collimated lights vs. diffused light - durst-pro-usa

A paper:

SOMETHING ABOUT BILL CLINTON AND LIGHT HEADS!

By Jens Jørgen Jensen, World Images Inc.

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CONTENTS. INTRODUCTION. ...............................................................................................................................4 THE PURPOSE. ...................................................................................................................................5 ANSWER TO A FREQUENTLY asked QUESTION. ........................................................................5 THE TERM “CONDENSER HEAD”. .................................................................................................7 THE EXPERIMENT. ...........................................................................................................................8 THE DIFFUSED LIGHT HEAD........................................................................................................12 SUMMARY........................................................................................................................................15 THE CONDENSER HEAD................................................................................................................16 SUMMARY........................................................................................................................................23 THE THEORY BEHIND THE USE OF CONDENSER LENSES. ..................................................24 FILM EXPOSURE AND PROCESSING FOR CONDENSER & DIFFUSED LIGHT HEADS. ....36 CONCLUSION...................................................................................................................................39 THEORY AND PRACTICE. .............................................................................................................41 Just a small hint!. ................................................................................................................................42

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INTRODUCTION.

If you were asked; “For what do you remember former president Bill Clinton?” What would then be the first thing you would think off? I believe that a very large percentage of the people asked that question will answer; “His affair with Miss Lewinsky”. Only those individuals with a deeper, more comprehensive knowledge of Mr. Clintons many fine accomplishments will remember the much more important facts. This goes to prove that a negative image is not only almost impossible to get rid off, it certainly also gives a distorted view of reality. Back in the late seventies the photographic community needed an excuse for abandoning “condenser printing”, in favor of the newly developed “Cold-light” and “soft-light-color-Dichro” heads. Instead of the truth it was said that Condenser light produced prints with “too much contrast”. The truth being that condenser printing is more labor intensive and the condenser system more expensive to manufacture. The new soft-light heads were promised to be not only less demanding in terms of labor input but also to increase the quality of the finished print. Therefore the “Too much Contrast” story became an explanation easy to believe. We are all naturally seeking to improve our work. Over time more negative terms such as “to grainy” and “to much dust” was added to the collective knowledge of the properties of “condenser printing” in order to boost the sales of the new “soft-light heads”. The negative image that unfairly was hung on “Condenser printing” is still hurting the entire photographic community. Many photographers and printers shun condenser printing based on rumors only. And are therefore loosing out on a real wonderful tool. And that is just what “condenser-printing” is – another tool. Not a replacement for diffused-light – not a universal tool - just another tool with different properties. As a tool condensers cannot be ignored because of its ability to reproduce fine detail.

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THE PURPOSE. The purpose of this paper is to establish the differences between diffused-light printing (Cold light) and Condenser printing. A discussion with the purpose of establishing, which one is superior, would have no meaning. Both types have their strong sides as well as their weak sides. Which in the end all boils down to taste and purpose. Only by knowing both types in detail is it possible to choose which type of head to use for which type of printing.

ANSWER TO A FREQUENTLY asked QUESTION. Should I purchase a Diffused light head or a Condense light source if I cannot afford both types? That question is actually superfluous! If you have a condenser head you also have a diffused light head. It is a 2-second operation to turn a Condenser head into a diffused light source. This is what you need to do: Install the condenser combination that will cover the largest format the enlarger is designed for Insert an Acrylic diffuser, type 1, between the negative and the last condenser lens. Viola you have the most perfect “diffused light source” you can dream off, lots of even diffused light. A Condenser head modified with a acrylic diffuser will create light of the exact same type as the light produced by a diffused light head using an acrylic diffuser. And it will do so with light of the correct wavelength for the paper. A diffused light source cannot produce Specular light (Condenser light). Even if you install condensers under the diffused light source you will not get the true Specular light.

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A NOTE.

In the remainder of this text I will be using the term “diffused-light-heads” as a common denominator for both “Cold-light-heads” and “Color Dichro-heads”. There is in reality no difference between the RESULTS produced by those two types of light if the Cold Light source produce light with the correct spectrum for the paper in use . Cold-light-heads and Color-Dichro-heads both produce light of the EXACT same quality. The light produced is called “Diffused light”. Insert link on spectrum.

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THE TERM “CONDENSER HEAD”. Before entering into a detailed discussion of the properties of “Condenser light” versus “Cold light” I would like to start by looking at the term “Condenser light”. The term “condense” is generally understood as meaning concentrate, compress or compact. And that is exactly what a condenser head does. A condenser light system is constructed in such a manner that; First the image of the lamp filament is enlarged to cover the negative in question, then the image of the lamp filament is condensed and focused precisely in the center of the enlarging lens – at the Nodal Point. This feature makes it a very bright and efficient light source. As such the name Condenser Head is a fitting name. But it could just as well be named “A projector head”. A slide projector works in the exact same manner as a condenser head. The condenser system in a slide projector is considered far less sophisticated than it’s counter part the “Condenser head” Modern paper emulsions are so light sensitive that printers, with a few exceptions, no longer need the condenser head for its high light output. Condenser heads are therefore no longer used primarily for their ability to concentrate the light. The fact is that condenser heads are now being used for their ability to reproduce fine details. The ability to reproduce fine detail is due to the light rays, emitted by the bulb, being arranged into parallel rays of light by the condenser lenses. The technical term for this effect is called Collimation. Therefore, I want to argue that the term “Condenser head” has become an inappropriate description of this type of light head. Since the rendering of fine details is the result of the light being Collimated the light head we all know as a Condenser head should correctly be named a Collimation head or if you want s Specular light head. It is in fact for it’s ability to deliver Collimated light we are primarily using the condenser head today. Photographers using “Printing out paper” for enlarging still rely on the Condenser head for its ability to produce intense light. (Visit J.Zdral at world-images-inc.com and see a presentation of his images. The directed light produced by a condenser lens or elliptic mirror is called “Specular Light”. The light produced by devices incorporating an acrylic diffuser is called “Diffused Light”. You may argue that the actual name of the light source is irrelevant for this discussion, which has the purpose of determining the differences between Specular-light and Diffused light. You are right of course. And, yes you are also right, it will not serve any purpose changing the name of “The Condenser head”. It will just ad confusion. Is not my intention either to suggest a name change. My intention with this somewhat long opening is to make you think of “The Condenser Head” in a very different manner than you are used to. If you bear with me and humor me by walking with me through the following basic exercises my reason will become clear further ahead in the text.

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THE EXPERIMENT. As a start I would like you to think about the sun as a photographic light source, which no one can argue it is. It is being used daily by millions as a gigantic “studio-lamp”. As a studio-lamp it is a spot light producing Specular light.

On this model showing the Sun and the Earth I have tried to illustrate that the Earth is so far away from the Sun, and the sun of such enormous size in relation to the Earth that the fraction of light rays reaching us are virtually parallel. This is not a theory of mine; it is a scientific fact. If this model had drawn true to scale the Earth would have been smaller and six feet away from the sun. (If you assign the sun the size of a quarter then the correct size of the earth would be approximately that of a pinhead, and the pinhead would be six feet away from the sun.) Then; Go outside on a clear and sunny day. Walk away from buildings into an open space. Hold your hand up and cover the sun with it. The backside of your hand, the side towards your face, will appear dark. Now do the same exercise when standing with your back against a light colored wall. You will immediately notice that the backside of your hand appear lighter when standing close to the wall than it did when standing out in the open. This is due to the light reflected off the wall is hitting your hand. Light is electromagnetic rays that are visible to the human eye. Electromagnetic rays can be bent, manipulated and reflected. Insert link to light page

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Now, find a piece of white paper or cardboard and bring it outside in the sun. Hold the paper perpendicular to the sunrays so that the sun shines directly on it. Then insert your hand between the paper and the sun. Your hand will create a clearly defined image of your hand (a shadow) on the paper. The further away you hold your hand from the paper the lighter and the less defined the shadow will be. Although the shadow is getting increasingly un-sharp with distance it maintains almost the same size regardless of distance. The fact that the shadow becomes a little lighter (washed out), the further away from the paper you hold it, is due to reflected light bouncing around in our environment. This experiment becomes even clearer if you use a piece of black paper instead of your hand. The hand is “light” on the back side and acts as a small reflector in it self, reflecting light back on the paper and making the shadow lighter than one created by a piece of black paper. IMAGINE your self dressed in black and standing inside a large box. The box is lined inside with black velvet and has it’s opening facing the sun. When standing inside the box the shadow of your hand would remain the same density (Degree of blackness) regardless of the distance to the paper. This is because inside the large box there would be no reflected light of any consequence.

The fact that your hand is making such a nicely defined shadow, and that the shadow stays virtually the same size regardless of the distance to the paper, is not just because the light rays are parallel when reaching your hand it is also proof that the light rays emitted from the sun (light Source) are virtually parallel when reaching your hand. If the light rays were not parallel the size of the shadow would increase or decrease when the distance from the object (hand) to the surface (paper) was changed. Further more; as you will see from the picture, above to the right, the sunrays are so FOCUSED (Parallel) that they are almost able to “print” a sharp copy of a negative on the paper. The sunrays (light rays) are collimated (parallel) when reaching your hand and the negative. Parallel light rays create a clearly defined shadow. Please go inside and repeat the experiments in front of a bank of fluorescent lights. Preferable use a bank of fluorescent lights with an acrylic diffuser in front of it.

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Hold a piece of paper directly underneath the Fluorescent light tubes, insert your hand between the light panel and the paper. You will immediately notice that there is hardly any shadow. In fact you will have to bring your hand almost in contact with the paper in order to create a trace of a shadow. Furthermore this shadow will have almost no resemblance with your hand. The shadow will be an almost shapeless bleak spot. There are two reasons for this. First, a bank of Fluorescent lights covered with a diffuser is creating diffused light. Diffused light is unable to create a clearly defined shadow because the diffuser is scattering the light rays in all directions. Secondly; the light rays reaching your hand are not parallel. Due to the size of the light source, in relation to your hand, the light rays reaching your hand from the edge of the light bank does so at a very flat angle. If you IMAGINE your self being able to stand as close to the sun as you were to the bank of fluorescent lights, then also the sun would create diffused light. And you would not be able to create a shadow on the paper with your hand. It is the objects distance from a given light source, and the intensity of the light source, that dictates the “quality” of the shadow.

The “Cold-light” heads and the “Color-Dichro” heads used in enlarging both create soft diffused light. In diffused light heads the size of the light source in relation to the negative is almost a 1:1 ratio. The light source is typically 10 to 20% larger than the format for which it is designed. “Condenser” heads are constructed in such a manner that it creates light of the same type as the light reaching us from the sun. It is designed to make it appear that the light source is infinitively far away from the object (negative) in order to make the light rays parallel and thus create a very strong shadow. Thinking about the hand in front of the Diffused light source; it would be hard to imagine that an even smaller object would be able to create a shadow at all. If you held a coin on a stick in front of the diffused light source there would be no shadow at all. The amount of reflected (diffused) light is so strong that it overpowers the black image (shadow) of the coin. Now think about what would happen with a spec of dust in front of that bank of lights!!!!!

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This is the Fluorescent light

fixture used for the picture on the previous page. To prove that this is actually a bank of Fluorescent lights we removed one tube so that the green cast, typical for Fluorescent, would show in one side.

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THE DIFFUSED LIGHT HEAD.

Based on the simple experiments we just conducted it is quite easy to comprehend why a “diffused-light- head” is capable of suppressing dust and impurities in negatives when printing. The dust spec is simply “washed” away with light. It would be a contradiction in terms to think that fine details in the negative would be maintained while dust specs are be washed away. If you examine a diffused light enlarger you will see that the position of the negative is equal to that of your hand under a bank of fluorescent lights.

The only difference: Compared to our primitive experiments an enlarger has one more object to take into consideration - the enlarging lens. An enlarger does not project the negative directly onto the photographic paper. We need a lens to focus and render a sharp and detailed image of the negative.

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In fact the enlarger lens assume the function of the paper in our experiment. The enlarging lens sees the negative silhouetted against the light source, just as our first experiment where we held our hand up in front of the sun.

The fact that the lens is focused on the silhouette does to some degree diminish the effect of the washout. However it does not eliminate “washout”. If introducing a lens would eliminate “washout” (Flare) you would not have to extend exposure and development times for negatives processed for “diffused-light” printing. Also, if introducing a lens would eliminate the effects of flare it would render all dust and foreign objects with a clear shadow just as the parallel light rays from the sun does. Mr. Burkett, Master Ilfochrome printer, suggested to ad to this chapter that; according to his personal experience some enlarging lenses even ad to the degree of diffusion. (Insert link to Burkett) A diffused light source will send light rays, bouncing around in all directions, through all the clear and less exposed areas in your negative. These non-parallel light rays will make the dense areas in your negative appear lighter (lower contrast) than they in fact are. The lens will see this flare just as the piece of paper did. That is the reason why you have to overexpose and overdevelop your negative when you use a Cold light or Color Dichro head for printing.. When you overdevelop your negative you increase the contrast in the negative. The increased contrast compensates, to some degree, for the “grayness” (lack of contrast) created by the flare. Cold light sources and Color Dichro heads create soft light. The correct technical term is “Diffused” light. Condenser heads create Collimated light (Parallel light rays). The correct technical term is “Specular” light.

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Simple diffused light heads are fairly easy to make and maintain. They are therefore available in a variety of different qualities. They can be made with a variety of different light sources, such as incandescent bulbs, fluorescent lights, neon tubes or halogen lamps. The most inexpensive kind is the type using neon or fluorescent tubes. Those types of light heads are quite adequate as long as the amount of light is not critical and as long as the evenness is not critical. Diffused light heads based on a single incandescent lamp or tube tend to be very uneven especially when used with a grade 3 to 5 variable contrast filter. When the diffused light head is made with one or more halogen lamps and when Dichroic filters are introduced in the light path the complexity and the cost of the diffused light head tend to go up drastically. The more expensive Color Dichro heads will produce extremely even light even at grade 5. A Durst Color Dichro Head is the most advanced Diffusion light heads on the market. Incorporating up to 6 diffusers it is by far the most even diffused light available. Modern Color Dichro heads belong to the group of light heads labeled “Diffused light heads”. They produce the exact same directional-quality of light as Cold Light heads. And as any other diffused light head whether it is using neon, fluorescent or incandescent lamps. When studying differences in the quality of diffused light heads it is very important to notice that the directional quality of the light produced by the heads will be the same, regardless of the mechanical quality, as long as they incorporate the same type of acrylic diffuser at the final stage in front of the negative. link to article about acrylic diffusers It is very possible to obtain different degrees of diffusion by exchanging the diffuser in use. A piece of “Milk-glass” can be used as a diffuser. A piece of sand-blasted glass can also be used as a diffuser. Acrylic diffusers come in a variety of opacities that create different degrees of diffusion. Acrylic diffusers of almost opaque white material will create the most diffused light. By introducing a opaque white acrylic diffuser in front of the negative, and AFTER the last condenser, even a Condenser head will produce diffused light. When comparing the quality of two diffused light heads using the same type of diffuser material only such qualities as mechanical sturdiness, filter repeatability, light evenness and light spectrum can make the difference. The mechanical quality of diffused light heads will be discussed in a separate paper. It is not the purpose of this paper to enter into a discussion of these aspects.

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SUMMARY. Soft-light is less of everything, less work; less spotting and less expense (compared to condenser-light). It is also less light and less sharpness, both real sharpness – detail - and perceived sharpness equal to local contrast. In some instances it is also less tonality, but that we will discuss later in the chapter; FILM EXPOSURE AND PROCESSING FOR DIFFERENT TYPES OF PRINTING. At one point diffused light is “more” – it is more flexible and easier to use than a Condenser system.

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THE CONDENSER HEAD.

A Condenser head is designed and constructed in order to create light of the same type and quality as that we receive from the sun. It is designed to create Collimated light of the highest possible intensity. Compared to a simple Cold light head a condenser head is a far more complicated unit. A Condenser head is of even more advanced design than the most complicated Color Dichro head as long as we do not consider such aspects of a Color Dichro head as electronic controls.

Before I go further into a detailed explanation I want to point out that my explanation makes itseem like using a Condenser head is overly complicated. THAT IS IN FACT NOT THE CASE.It is very easy to use a Durst Condenser system. All you need to know is how to read theCondenser tables (The tables are attached) and that you can adjust the position of the enlarginglamp to obtain the most even light distribution on the baseboard. Adjusting the lamp is donevisually and only requires that you know what to look for. The explanation is attached. If this paper is giving the impression that using a condenser head is complicated it is most likelybecause I am so fascinated by the craftsman’s ship involved in designing a Condenser head. Plusthe fact that I like the technical details. The technical details are of no real importance for theactual use of a Condenser head. The real important message is found under in the conclusion ofthis paper.

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When you use a Condenser head for printing, the negative is not just placed in front of a bank of lights. It is in fact inserted into a complete optical system. When you install a lens in sequence with another lens you are in fact creating a new different lens or optical system with different properties than those of the individual lenses. Whether a condenser system consists of 1, 2, 3, 4 or 5 lens elements it is transformed into an entirely new complicated optical system as soon as the enlarging lens is introduced into the system. The enlarging lens becomes “just another lens” in the entire system.

The purpose of the condenser system is to:

A. Focus the lamp or lamp filament right in the center (Nodal point) of the enlarging lens. B. Place the negative exactly where the light rays are produced with the highest degree of

Collimation. If we examine a condenser head we will see that the negative is positioned exactly at the plane where the light rays exit the last condenser lens. This is also the plane where the light rays are most parallel. A condenser head manipulate the light rays in such a manner that they become almost parallel and resemble those received from the sun. The plane where the bundle of light rays is most parallel is also the plane with the least stray light. From that, and our previous experiments, follows that the “shadows” created by the negative, will be seen by the lens with their maximum opacity. Or in other words with the least flare or “washout”. I use the word “shadow” because the negative is merely a substrate holding silver silhouettes of varying opacity. A silhouette could also be your hand inserted in the light beam.

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The challenges involved in construction a Condenser system is:

A. To focus the lamp or lamp filament right in the center (Nodal point) of the enlarging lens. B. To place the negative exactly where the light rays are produced with the highest degree of

Collimation. C. To position the lens at a point where it renders a sharp print simultaneously with demands A

and B being fulfilled. D. To incorporate condenser lenses with a diameter large enough to cover the negatives in

question while at the same time maintaining the size of the system small enough to be manageable.

E. To enable different degrees of enlargement for each size of negative. F. To create a bundle of light rays with the highest possible degree of Collimation.

How these six demands are fulfilled will be briefly described in the next chapter. The most common problem to solve in condenser systems is to get the diameter of the condenser-lenses large enough while at the same time getting the focal length short enough to make it practical to use and produce. Durst has solved this problem very elegantly. Not only have they managed to construct a condenser head of very compact size they have also managed to produce a system that covers almost every imaginable combination for lens and negative sizes. For each negative format Durst is using THREE Plano Convex condenser lenses. With a few exceptions the convex side is facing the convex side when two condenser-lenses are paired. When enlarging with a diffused light head any enlarging lens with a circle of coverage large enough to cover the format in question can be used as long as the diffuser is larger than the negative. This is not the case with condenser systems. When using a condenser head for printing only certain combinations of negatives and lenses can be used together. Even though a wide-angle lens is capable of covering a given negative it may not be

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possible to use that exact combination. This is because the DIAMETER of a condenser lens, with a focal length of the right size to place the lamp filament in the nodal point of a given enlarging lens, may be to small for the negative in question. Example: The EL-Nikkor 240mm f5.6 lens is more than capable of covering an un-cropped 8x10” negative. However the diameter of the condenser lenses, with a focal length capable of placing the lamp filament in the nodal point of the 240mm enlarging lens, is to small. The diameter is shorter than the diagonal of the 8x10” negative making the use of this particular combination of lens and negative impossible. If the filament of the lamp is not placed within a certain distance from the center of the enlarging lens you will get extreme light fall off, equal to black corners, on your print. Enlarging lenses with a focal length of 240mm are used with Durst Condensers #250 and #380 in pair, the convex sides facing each other. The Durst Condenser model 250 has a usable diameter of 250mm and a focal length of 375mm. The Durst Condenser model 380 has a usable diameter of 380mm and a focal length of 570mm. The diagonal of an 8x10” negative is approx. 325mm, and thus to large for the diameter of the Durst condenser model 250. Other than those few restrictions the Durst condenser system is so ingenious and precisely designed that all you have to do, to adapt the head to a new size negative or print, is to change the size/combination of the condenser lenses and the enlarging lens.

DURST 10x10” condenser head, DURST LACON 380 for 10x10” and 8x10” printing and DURST LATICO 240 condenser for 5x7” printing.

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The Durst system has a provision allowing the lamp to be adjusted in three planes and to be rotated. This feature is placed outside on the back of the condenser head and is very easy to access. All functions are adjusted with three different knobs or handles. The lamp can move; Up and down, left to right and from front to back. In a Durst condenser system these adjustment are first of all used for adjusting the position of the bulb, in relation to its physical dimensions. Bulbs are manufactured with small tolerances as to the physical dimensions and filament placement. OPAL bulbs may need to be rotated in order to find the most even section of the opal coating. Secondly the movement from the front position to the rear position is used to adjust the position of the lamp filament in relation to the position of THE ENLARGER lens’ Nodal point. When focusing for prints of different size the distance from the Nodal point of the lens to the negative varies and thus the distance from the condenser lens to the Nodal point. In order to maintain the lamp filament exactly in the nodal point it is necessary to be able to adjust the position of the lamp in relation to the Condenser system. The fact that the lamp needs adjustment for each print size makes it more complicated to use than a diffused light head. If you are fortunate to posse a Durst Condenser head you can allow your self to IGNORE adjusting the lamp when changing the degree of enlargement IF you use an OPAL lamp or another diffused light source. You then only need to adjust the lamp when installing a new lamp. The Durst Condenser heads are so precisely designed and manufactured that; If the OPAL source is adjusted correctly for your most commonly used print size the small variation involved with other sizes will only affect the degree of Collimation and the light intensity slightly. Light evenness is not affected. This holds true even when changing from one set of condensers to another. When using a POINT-LIGHT lamp it is necessary to adjust the lamp even for small variations in print size. A POINT-LIGHT lamp is a type of lamp with a clear cone and a small tightly woven filament. Condenser light sources come in a variety of qualities. In contrast to diffused light sources the mechanical quality of the condenser light head plays a very important role. Without getting to deep into it such a thing as centering of the lenses are extremely important for the performance of a condenser system. It is extremely important that the quality of the optical design is the best possible because of its influence on the degree of collimation created. The better the optical design the more pronounced the collimation will be. You can create different degrees of collimation just by adjusting the distance from the light source to the condenser lenses or by adjusting the size of the bulb – actually two sides of the same case because a large bulb will seem smaller if placed further away from the condenser. But still not quite since bulb placement also plays an important in relation to the focal length of the condenser lenses. The bulb has to be placed at a certain distance from the condenser lenses in order to obtain the best collimation and the highest light out-put. The degree of collimation is also influenced by the type of bulb used. A large OPAL bulb will create light that is less collimated than light created with a small OPAL bulb. The larger the OPAL bulb the less critical such aspects as bulb placement becomes.

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When using an OPAL bulbs of increasing size in a condenser system you gradually move away from collimation. The larger the cone of the OPAL bulb, the smaller the degree of collimation will be. True Collimation is based on an “infinitively small” point of light. As the “point of light” increases in size more and more light rays are spilled outside the concentrated bundle of Collimated light rays that we seek to obtain by using a Condenser system. The light spilled to the sides increases the amount of flare in the condenser system. By using an opal bulb in a condenser system we are in fact creating a “projected diffused light”. Which can be considered an intermediate between a true diffused light source and a true Specular light source. Some poorly designed condenser systems require an opal bulb in order to function properly. They need the large cone in order to produce light all the way into the corner of the format that is being printed. When a bulb with clear glass is used in a condenser system the light is named “point light”. This is because the condenser system will see the actual filament of the lamp as a small bright point. The smaller the filament the stronger the Collimation will be. The higher the degree of collimation the higher the contrast will be of the image projected on to the printing medium, paper or film. By using coated condensers, and/or coated mirrors, and/or coated negative glasses the collimation can be further increased proportional to the number of surfaces that are coated because FLARE inside the condenser system is being reduced exponentially. The DeVere Condenser System: The DeVere condenser system is as advanced as the Durst system. In the DeVere system it is possible to use a wider selection of lenses with the same set of condensers. A 240mm enlarging lens can be used to enlarge an 8x10” negative. This flexibility has been obtained by using condenser lenses with a very large diameter and therefore a relative large focal length also. Focal length and diameter of a lens are proportional. By constructing the lamp-housing in such a manner that the distance from the bulb to the condenser lenses can be adjusted over a very long range of 600mm = 24 inches DeVere has obtained to design a condenser system of extreme quality and flexibility. The DeVere system will even accommodate a 480mm lens used with an 8x10” negative. As a matter of fact; in this system all lenses of different focal lengths can be used with the same set of condenser lenses and as such there are practically no limitations as to the combination of condensers-lenses and enlarging lenses.

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The extreme flexibility was been obtained by sacrificing size and simplicity. The large diameter of the condenser lenses not only dictated a large focal length but also that a total of four condenser lenses had to be used. The four lenses are used in two pairs. Furthermore very complex condenser lenses had to be used. The DeVere system is using two Positive-Meniscus lenses and two Plano-Convex lenses. The two sets of two condenser lenses each have a diameter of 400mm (15.74”) and a focal length of 1600mm (63”) per set. Because the two sets are paired the total focal length is reduced to approximately 800mm. The size and the weight of the condensers make it unsuitable for vertical enlargers. The distance from the enlarging lens to the lamp, when used with a 360 mm lens, is more than 2000mm, (6,5 feet.) The system is therefore only suitable for horizontal enlargers. In addition to the two large sets of condensers the DeVere system incorporates two additional booster lenses for smaller formats. The complicated construction also sacrificed economy to some extend. The system is prohibitively expensive. It was designed and built for DeVere by legendary lens manufacturer Rodenstock. If a similar set of condensers were to be obtained today the price would be well over $25,000.00. And this price could only be obtained if a total of 25 sets were ordered at the same time! The DeVere condenser system is quite complicated to use. The lamp needs to be re-focused for every single change made in the enlarging-lens and/or degree of enlargement. This is especially true when a true point light lamp is used. (Insert link to point light source). The results produced by both the Durst and the DeVere Condenser heads are superior to any other type of light heads as far as detail and sharpness in concerned. For me personally it is an indescribable joy working with these two systems. Slow and challenging but very rewarding.

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SUMMARY. A condenser head produce prints with higher contrast and more detail than any other light source because the light rays are Collimated. The degree of collimation is determined by:

1) the type of lamp being used 2) the mechanical quality of the condenser head 3) the degree of internal flare in the condenser head.

The degree of internal flare is determined by the quality of the design and by how many of the lens surfaces that are anti-reflex coated. It is possible to adjust the degree of collimation by using lamps with varying filament size as well as using opal lamps or diffusers. A condenser head is not as flexible as a diffused light head when it comes to choosing enlarger lens. Using a condenser head require that the manufacturers table of possible condenser lens and enlarger lens combinations be followed. Using a condenser head requires as a minimum that a new lamp be adjusted for position before being used for printing. It is possible to turn a Condenser head into a diffused light head in seconds by introducing an acrylic diffuser between the negative and the last condenser lens.

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THE THEORY BEHIND THE USE OF CONDENSER LENSES. A “condenser” is a lens just as the lenses you use on your camera, a very simple lens but never the less a lens Any type lens can be used in a condenser system. These are the most commonly used lens types used for condenser heads.

All Durst condensers are PLANO-CONVEX, Type The DeVere system is using both PLANO CONVEtype 5. If parallel light rays from a distant light source, ex. thean image of the light source behind the lens.

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#1, PLANO CONVEX #2, UN SYMETRICAL DOUBLE CONVEX #3, SYMMETRICAL DOUBLE CONVEX #4, NEGATIVE MENISCUS, thin center and thick edge. #5, POSITIVE MENISCUS, thick center and thin edge.

1.

X and POSITIVE MENISCUS, Type 1 and

sun, is projected through a lens it will create

You have probably seen this effect when using a magnifier glass to start a campfire. The bright spot created by the magnifier is in fact the image of the sun that is focused as a small bright hot spot. In a condenser system this property is used in reverse. The lens is used to turn the globe of light emitted by a lamp filament in to a bundle of Collimated light rays. The lamp is placed at the point of focus and is projecting its light through the lens from the flat side of a PLANO CONVEX lens. When you focused the image of the Sun with the magnifier you may not have noticed that the image of the sun was not entirely sharp. Looking closely would reveal that it had a “halo” around it. The halo is due to Spherical Aberration. All lenses are born with a series of defects in relation to focusing an image sharply. Condenser lenses and magnifiers are very simple lenses and tend to have quite a lot of spherical aberration as their worst fault. Spherical aberration is a lens fault causing the light rays passing through it to focus in two different planes. A “condenser” is a lens-element just like the lens-elements used in any taking or enlarging lens. However it is most often a cheaply made lens and of lower quality, than a lens element used in a camera or enlarging lens. In camera and enlarging lenses Spherical aberration is minimized and controlled by using different types of glass and counter acting with several lenses of different shape and type. When designing an advanced condenser system the Spherical Aberration is controlled in a different manner. By placing the lamp ¼ Focal Length (FL) inside focus, which is away from the point of focus in the direction of the condenser lens, it is possible to obtain almost true Collimation with one condenser lens. Using two condensers in a pair further reduce the spherical aberration to 25% of the aberration created by one lens. One would naturally think that the light would spread in a wide fan as the size of the light cone is increased. The reason this is not happening is that the light rays now has to battle the S.A and therefore is turned into a bundle of almost parallel light rays. Already now you can start to see the relevance of Durst using two PLANO CONVEX condenser lenses in a pair and of supplying a way of adjusting the distance from the lamp to the condenser lens. By using two Plano Convex lenses in a pair Collimation is increased because S.A is decreased. If we had not decreased S.A it would have caused a lot of light to spill to the sides and thus create flare and loss of light.

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The two drawings above illustrate how S.A is controlled by moving the lamp. Looking at the drawings you may get the impression that moving the lamp will solve all problems because it is shown that the light beam are almost parallel. Unfortunately true Collimation is only possible with a true “point” source of light. A true point does not exist. If a point is visible it has to have a size. The size of the point ( The light filament in a lamp with a clear cone or the size of the cone on an OPAL bulb.) creates a new problem we have to look at, in order to understand what makes a Condenser head function.

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The light rays emitted from any given point on the lamp filament, or the cone of an OPAL lamp, is creating it’s own set of parallel light rays. This model shows how a “theoretic true point” would render the light rays.

Lamp filament.

The next model shows how a “theoretic true point” would render the light rays if it were placed off center in relation to the physical center of the condenser lens.

As you will see; the light rays created outside of the center of the lamp filament would still be a bundle of parallel rays however they would not all be seen by the next lens in the system because they are not parallel to the rays created in the center of the filament. They would instead bounce off the sides of the inside of the condenser house. That is why a condenser head and all photographic lenses are black inside – to reduce flare.

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Now – if you IMAGINE the filament as an infinitive amount of tiny points. Then you will understand;

1. That flare will exist even in the most perfectly designed condenser system because all lamp filaments have a size. And therefore there will be light rays leaving the primary bundle even though they are parallel.

2. That the smaller the filament the more the final light cone will approach true Collimation.

Because the smaller the filament is the smaller the amount of parallel light rays leaving the primary bundle.

3. Why anti-reflex coating is helping in decreasing the flare level.

The optical engineers that designed the condenser systems worked with and used the fact that part of the light would be diverging. They used this property to create enough coverage for the negative in question with the shortest possible distance from lamp to negative. Let us look at how they did that:

The angle of divergence and the resulting size of the light cone can be calculated. Angle of Divergence = S ⁄ R Radians. Example: S = 4mm, R = 380mm and the filament needs to be projected 380mm (1 FL) to be

positioned in the aperture of the lens.

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Angle of Divergence = 4 ⁄ 380 Radians = 0.01052631578 Radians Light spread = 380 x 0.01052631578 = 4 mm + diameter of lens = 250 mm Diameter of light beam at 380mm = 254mm Now let us look at the actual condenser lens sitting right in front of the lamp in a Durst 10x10 Condenser head and let us assume that we use a DULAMP 1200-TOP which has a filament with a size of 15x15mm. The diameter of the filament would be approx. 21mm. And let us assume that Durst had placed the lamp in the correct spot as previously determined, which was ¼ inside focus towards the first condenser. S = 21mm, R = focal Length of LAZUCO 181 condenser = 250mm. The diameter of LAZUCO is 181mm. The distance from the lamp to the first of the two LACON 380 condensers is approx. 1100mm. The diameter of the LACON 380mm is 380mm Angle of Divergence = 21 ⁄ (250x 0.75) Radians = 0.112 Radians Light spread = 1100 x 0.112 = 123 mm + diameter of lens = 181mm Diameter of light beam at 1100mm = 304mm We would need the diameter of the light cone to be exactly 380mm to cover the entire surface of the LACON 380mm lens. The light cone is obviously to small to cover the entire condenser. The diameter of a 10x10” negative is 14.14” = 359mm. Assuming that the natural light fall off created by the enlarging lens is equal to the natural light fall off created by the shooting lens (which is rarely the case in practice) we would need the condenser to be almost totally covered. How did Durst fix that? They moved the lamp closer to the first condenser! (And therefore introduced a heat filter before the first condenser). Angle of Divergence = 21 ⁄ 115 mm Radians = 0.183 Radians Light spread = 1100 x 0.183 = 201mm + diameter of lens = 181mm Diameter of light beam at 1100mm = 382mm If you try and re-calculate the last example with the distance being 125mm from the filament to the first condenser you will immediately see why accurate positioning of the lamp is so important when we talk about point light sources.

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You will also understand why the PULAMP with a diameter of the filament of less than 7mm will not cover 8x10” formats. And that the PULAMP can only be used for formats with a diameter not exceeding 248mm = max. 7x7” neg. Let us try to calculate the 10x10” situation using an OPAL lamp with a 4” cone. Angle of Divergence = 100 ⁄ 75 mm Radians = 1,3 Radians Light spread = 1100 x 1,3 = 1466mm + diameter of lens = 181mm Diameter of light beam at 1100mm = 1647mm With a light cone of that size there will be a lot of stray light / flare inside the condenser head. Also, you can use any f-stop even f5.6 and still have the entire aperture filled with light. You have in effect created a “projected diffused light” which is an intermediate between Specular light and diffused light. The next issue we need to look at is the actual size of the filament that are being projected into the Nodal point of the lens = right at the aperture Focusing the filament right in the center of the enlarging lens has the purpose of maximizing the amount of light being output to the printing surface (photo paper or film.) Since enlarging lenses of different focal lengths have different sizes of the Iris Diaphragm (Aperture) the same lamp filament needs to be projected with different sizes depending on the lens in use. Ex. The diameter of the aperture in a 300mm Schneider Componon is approx. 50mm at f5.6. The diameter of the aperture in a 360mm EL Nikkor is 65mm at f5.6 and a 150mm Rodagon has an aperture with a diameter of approx. 25mm at f5.6. The area of the aperture opening at f8, in any given lens, will be half of the area at f5.6. The area at f11 will be half that at f8 and so on. f5.6 f8 f11 Most condenser systems are designed to work at a certain given f-stop when using a point light lamp. Most often this f-stop will be f11. When using an opal lamp you are free to use any f-stop on the lens.

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When calculating the distances for the condenser system we will always calculate with distances that are LESS than one focal length. The distances from the lamp to condenser #1 and from the Virtual Filament to the center of the main condenser lens will per our previous discussion always be less than one focal length. Therefore we will have to use the following formulas: I1 = (M-1) x EFL O1 = I1 / M M = degree of enlargement = Image size / Object size. EFL = effective focal length of lens in question. When calculating the distances for the Image system (negative to print) we will always calculate with a distance from the negative to the enlarging lens which is LARGER or equal to the focal length of the enlarging lens. Only when focusing at infinity (making a print where objects are life size) is the distance (bellows extension) from the negative to the Nodal point equal to the focal length of the enlarging lens. Therefore we will have to use the following formula: I2 = (M+1) x EFL O2 = I2 / M

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M = Image size / Object size. EFL = effective focal length of lens in question. In both cases the overall length of the system may differ slightly from the value obtained by adding the Object distance to the Image distance. If you use a condenser system to make prints that are the same size or smaller than the negative a whole new set of conditions will take effect and calculations made for those situations. In practicality you do not need to worry about all this theory. Durst has already provided a table showing all the necessary condenser and enlarging lens combinations. Refer to you enlarger manual for details. Calculating the EFL (Effective Focal Length) of a lens (set of condensers) is quite simple.

The Effective focal length, (EFL), of a set of identical lenses will always be equal to ½ focal length of one of the two lenses.

The effective focal length (EFL) of three or more lenses, in contact or nearly in contact, can be calculated with the following formula: Three lenses 1/f combined = 1/f1 + 1/f2 + 1/f3 1/f combined = 1/100 + 1/200 + 1/300 = 11/600 invert f combined = 600/11 = 54.54mm effective focal length

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When calculating the size of the projected lamp filament for an a-focal condenser system things grow a bit more complicated. In order to understand this model in relation to the other models shown it is very important to be aware that any of the two lenses (F1 and F2) can be a set of condenser lenses in contact or near contact. It can be a set of three or four condenser lenses for that matter. If that is the case then the EFL of this lens is first calculated with the previous formula. In this case M = F2 / F1 = 570 / 250 = 2.28X Therefore, if we used a DULAMP 1200-TOP with a 21mm filament we would produce a projected filament with a size of approx. 48mm in diameter. This would fit the 300mm Schneider Componon at f5.6. Now let us assume that the negative is positioned 70 mm under the last condenser lens which would position the negative approx. 500mm from the Nodal point of the enlarging lens. With a 300mm lens and a 500mm bellows extension we calculate the print size in the following manner. We know three parameters: Effective focal length of the enlarging lens is 300mm The long side of our negative is 10” = 254mm (8x10”) The bellows extension is 500mm Then we need to find M, which is the degree of enlargement.

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M = EFL / (O2 – EFL) M = 300 / (500 – 300) M = 300 / 200 M = 1.5 X Thus we can print a 12x16” print from an 8x10” negative with this specific combination of lenses and still maintain all parameters optimal. The following is a drawing of a Durst 10x10” condenser head. The drawing is true to scale. The blue frames in the head indicate the two surface coated mirrors. The larger of the two mirrors can be tilted down to cut the light path short and concentrate the light on smaller formats.

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With their two condenser heads – LACO 57 and LACO 1010 Durst has taken “Condenser-printing” to the highest possible level obtainable within reasonable means. The heads are extremely easy and comfortable to work with and they are of very high mechanical and optical quality. The Durst system standard configuration is three condensers and two mirrors. The use of two mirrors makes it possible to change the distance from the lamp to the nodal point off the lens. The Durst system offers 9 condenser-lenses of different focal length accommodating almost any focal length lens on the market. The most usual condenser-lens is Plano convex. For each negative format Durst is using THREE Plano Convex lenses. With a few exceptions the convex side is facing the convex side when two condenser-lenses are paired. When using two identical condenser lenses, as a pair in contact, you reduce the TOTAL focal length to half of the focal length on one condenser while maintaining the diameter of the “longer-focal-length” condenser lens. This is a very important and largely overlooked aspect of constructing a condenser head. Ex. A Durst Condenser head is using a pair of two identical condenser lenses each with a focal length of 570mm for 8x10” and 10x10” printing. This focal length of the condenser lenses are necessary to make the diameter of the two lenses large enough to cover a 10x10” negative (254mm x 254mm). When pairing the two lenses the Effective Focal Length (EFL) is reduced to 285mm which is very important in order to fit the optical system inside a compact condenser head and to make it possible to make LARGE prints from 8x10” negatives. Please see the calculation on the previous page. Had the focal length not been reduced the lamp would have had to be placed almost four feet away from the condenser lenses and the enlarging lens would have had to have been placed another almost four feet away from the condenser lenses. Thus making the whole system at least nine feet long. When designing a real effective condenser head the challenge is to be able to maintain the image of the lamp filament in the center of the lens while at the same time being able to focus the negative on the paper. Therefore only certain focal length enlarging lenses work correctly with certain combinations of condenser lenses. The Durst Condenser model 250 has a usable diameter of 250mm and a focal length of 375mm. The Durst Condenser model 380 has a usable diameter of 380mm and a focal length of 570mm. Durst has further introduced a third condenser lens quite close to the lamp. The function of this lens is both to enlarge the size of the lamp behind it but also to increase the degree of parallelism (Collimation) of the light rays. Enlarging the lamp or the lamp filament is equal to creating a light cone large enough to cover the format in question as discussed earlier. One of the mirrors, the large mirror, can tilt from its top position to a 45 degree angle and thus reduce the distance from the first condensers to the two second condensers. This feature is used when the 10x10” head is used to print smaller formats, 5x7 and smaller.

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FILM EXPOSURE AND PROCESSING FOR CONDENSER & DIFFUSED LIGHT HEADS. Manufacturers of Cold light heads propose that the film manufacturers recommended exposure and development, for a given BW film, should be extended approximately 30%. Some even recommend a 50% increase. Insert link to Aristo page http://www.aristogrid.com/coldlight.html In this context it is an interesting detail that many fine art printers, teachers and textbooks recommend to reduce film speeds to 50% of the manufacturers recommended speed – that is one f-stop overexposure. Fred Picker from Zone VI even suggests rebuilding your light meter to show one f-stop less light than factory intended. I am sure these recommendations are entirely due to the fact that those giving the advice is using a diffused-light head for enlarging . Extended exposure and development of negatives produced for diffused-light printing is necessary in order to obtain a level of exposure and contrast capable of producing a normal contrast range on a “grade 2” paper as compared to a CONTACT print. With other words; It is necessary to modify the film manufacturers optimal exposure and optimal development data in order to make the negative suitable for diffused light printing. That is a true oxymoron. At first the manufacturers (and users) of Cold light heads praise this light source for its ability to suppress grain and dust and then it is recommended to overdevelop the negative, which in return will increase grain and decrease detail in the negative. It is common knowledge that exposure increased above the level recommended by the manufacturer will decrease the resolving power of a given film. As a matter of fact an “under exposed” film will have greater resolving power than a correctly exposed film. Any one disputing that as a fact only need to put a 200 ASA standard color film in a 35mm camera and shoot a series of nine exposures from –4 over N to +4 f-stops overexposure. And have the film developed in the nearest one-hour kiosk. You will immediately see that details decrease with the increased exposure. As soon as you enter in to “over exposure” also the grain increase drastically Some experts will claim that the loss of resolving power, resulting from the increased exposure, will be countered by the increase in edge-contrast created by the prolonged development time necessary for BW film processed for diffused light heads. I disagree with that argument when talking about pictorial images. There may possible be grounds for that argument when judging purely technical images such as pictures of resolution charts. Resolution charts do not take into consideration tonality. Furthermore high contrast edges on the grain is to be avoided when the grain is located in white or light gray areas. Clearly no one will dispute the fact that both increased exposure and increased development results in a more defined grain structure.

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The effect of increased exposure and development is that; 1) more silver halides are exposed than needed 2) the silver actually exposed is made less transparent. 3) The silver grains actually exposed starts to “bleed” and “Clog”.

A single grain of silver can only “absorb” a certain amount of exposure. When it has received its maximum amount of exposure and its maximum amount of development it becomes inactive and further increase in density (on the film) can only be obtained by effects known as “bleeding” and “clogging”. Bleeding is what happens when a silver grain already saturated is bombarded with more light waves, the exposure starts to flow over to the next lower level of unexposed silver halides. Clogging is what happens when two grains of silver, located next to each other receives enough exposure and enough development in order to bleed into each other. Let me try and explain that in a more graphic way; IMAGINE that you were to photograph TWO tiny tiny dots (.) The dots are white and placed next to each other in the middle of a large piece of completely black paper or fabric. The distance between the two dots is equal to the diameter of one dot. The film manufacturers recommended exposure and development would produce a negative in which the two white dots would receive just enough exposure and development to reproduce as two white dots with the same density, as the two original dots, when the negative is contact printed. And just enough exposure and development for the black paper to reproduce with the same density as the original black paper when the negative is contact printed. It is very important to be aware that published film speeds and processing times, for a given film, are designed to produce a negative suited for contact printing. The type of light used to make the exposure also influences the physical quality, sharpness and contrast, of a CONTACT print. However the differences are minute and I have chosen not to take into account this aspect in this discussion. Now let us IMAGINE that we overexpose and over develop a second negative shot of the two dots. This time we give the negative half an f-stop more light and 30% more development than the manufacturers recommendation. The increased exposure would allow silver grains around those actually producing the white dots to also start picking up light, and thus ad to the size of the dots. The increased development would not only increase the density of the two dots it would further ad to density of the silver grains picked up around the actual image of the two dots. Before you know it, each of the two tiny dots would have grown 50% and would thus have become ONE larger oblong looking white dot. You can make a very easy experiment that will show the effect of “bleeding” and “clocking”. Put a single hair in your enlarger (any enlarger will do) and make a print where the hair is clearly defined. Then gradually increase exposure or development and you will see at first that the hair starts to look fuzzy and then it will disappear completely and you are left with a completely black print

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Extended development also diminish tonal separation. When development is extended values that would normally be placed lower on the curve are pushed up in the area of the curve where no separation is possible. This effect and the increased grain is particular noticeable in a print/negative with normal shadows and white clouds on a blue sky. A minimally exposed and developed negative is therefore always to be preferred.

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CONCLUSION.

We have seen that diffused light sources, Cold-light and Color Dichro heads, create very soft results because of the extreme amount of flare created. We have seen that Collimated light or Specular light-heads, Condenser heads, create high contrast reproduction because of the elimination of flare due to the light being collimated. We know that the film manufacturers recommended speed and development times are designed to give us a negative that will produce the best contrast in a CONTACT print. Our common sense tells us that BOTH Specular light and diffused light create more flare than a contact print does because of the simple fact that there is no room for flare to be created when the negative is in contact with the printing paper. With this information it makes sense;

1) That we have to INCREASE the manufactures recommended development times MORE in order to make a negative suitable for a diffused light source.

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2) That we have to INCREASE the manufactures recommended development times LESS to

make the negative suitable for a Specular light source. We know that “less exposure” and “less development” will give us a negative with “more tonal separation” and “more resolution”. We know that the factors influencing the physical qualities of a negative influence a print in the exact same manner. Therefore the conclusion must be that: If we are looking to produce prints with the largest amount of detail, the smoothest grain and the longest tonal scale we must expose and develop our negative as little as possible. Printing minimally exposed and developed negative will require a lower paper grade if printed with a Specular light source than it will if printed with a diffused light source. Therefore the best technical quality obtainable in a Black and White print is obtained from a minimally processed negative printed on as low a paper grade as possible this combination is only possible with a Specular light source - a Condenser head. Of course there are other aspects of a print than technical quality. There are feelings and expectations. And artistic expressions. In a portrait we do not expect to see every little blemish in the skin. It hurt our feelings if we are “reproduced” to detailed.. In a picture of a spare part recovered from a plane crash we expect to see as many details as absolutely possible, and we want the tonal gradation to be as true as possible because it enables us to make the best assessment of that particular parts involvement in the crash. It is all about expectations, visualization and choices.

With knowledge about our tools AND the right tools we are able to make quality choices.

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THEORY AND PRACTICE. Reasonable skepticism is healthy. And as the involved reader I am sure you are going to say; “That is all very fine, but it is theory” Yes and No, of course it is all theory but it certainly holds true in practice. All of the above is my personal experience. I worked “backwards” when learning all this. From my daily work with the medium “I knew all this “theory” in practice”. It was not until later that I had to prove my experiences by establishing the theory. You your self was engaged in the light tests. Here is an outline of the tests I made to prove the film theory. I suggest that you make similar tests to convince your self. I set up my 8x10” Linhof camera and focused on an image that I had constructed with the purpose of determining the effect of exposure and development on resolution, tonality and graininess. I made an image of a piece of black paper and a piece of white paper, which I placed on the ground. I left approx two inches (5cm) between the two pieces of paper so that I could see the ground between the two pieces. On both pieces of paper I placed a large Kodak gray scale, a piece of a Kodak Grey card, a white flower, a red flower, a fresh branch with green leaves, a piece of chicken (could not use human flesh due to the duration of the experiment), some ground pepper and ground salt, the smallest pieces was hard to see with the naked eye and finally a US Air force resolution target and pieces of a resolving power chart. I exposed a total of 35 negatives. Exposure Exposure Exposure Exposure Exposure Exposure Exposure Development

- 1.5 - 1.0 - 0.5 N + 0.5 +1.0 + 1.5 -40% - 1.5 - 1.0 - 0.5 N + 0.5 +1.0 + 1.5 -20% - 1.5 - 1.0 - 0.5 N + 0.5 +1.0 + 1.5 N - 1.5 - 1.0 - 0.5 N + 0.5 +1.0 + 1.5 + 30% - 1.5 - 1.0 - 0.5 N + 0.5 +1.0 + 1.5 + 60%

Five negatives was exposed at the exact value that my factory adjusted Minolta Spot meter, directed at the Kodak Grey Card, indicated as the normal exposure based on the Agfa’s indicated film speed of 100ASA for AGFAPAN 100. After the first five another five negatives were exposed at each of the following settings; -1/2, -1, -1.5, +1/2, +1, +1.5 thus making it a total of 35 exposures and five identical sets of film. These five sets I then developed at N (Agfa’s recommended development time in the recommended developer), N-20%, N-40%, N+30% and N+60%.

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(If your purpose is just to establish the truth of resolution, graininess and tonality you can make this experiment faster with five rolls of 120 or 35mm film. My purpose was also to actually test my system and find my “normal’s”. I later repeated the entire experiment with Pyro development.) After development I contact printed the five sets of prints. I established my contact printing exposure by printing to a density that just accurately would render zone 0, on the Kodak grayscale, as maximum black. With the knowledge that shadow details are controlled by exposure and contrast by development I exposed all contacts absolutely identically. I took great measure to insure accurate processing of the prints. I then choose the “best” CONTACT print of each set of contacts . Leaving me with five “best” contacts. Then the hard work started. I printed all negatives first with a Durst Color Dichro head and then with a Durst Condenser head. I used the same enlarger and the same lens for both series. I again printed for maximum black in Zone Zero, but this time I also printed for tonality. I printed for maximum black and chose paper grade to maintain detail in my high lights. I used a Durst PCM1001 analyzer to avoid having to make test strips from each single negative. The PCM1001 is the only easel meter, to my knowledge, that calculates Reciprocity when the exposure time is changed. From those 2 x 35 prints I choose the TWO prints that most accurate resembled my best contact print. It was a quite amazing discovery! In order to give you a chance to conduct the tests your self and to give my self a chance to redo the tests with TMAX I will wait with publishing my detailed results till November of 2000. My AGFA PAN tests were made back in 1985.

Just a small hint!. A 10X enlargement of the best negative, developed for and printed with condenser light, showed less graininess and more details than a 5X enlargement from the best negative developed for diffused light. And it did so with minor increased tonality!!!! Jens J. Jensen Hillsboro, March 29, 2002.

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Literature list: Photographic Sensitometry by Todd and Zakia. Kodak manuals, Agfa Litterature Lens design Fundamentals by Rudolf Kingslake. Optics in Photography by Rudolf Kingslake.

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Table of condenser combinations for the Durst Laborator 184.

VERTICAL PROJECTION

Lens f = mm /

inches

Negative size mm / inches

Linear magnification

minimum maximum

Condenser Combination

+LAZUC0 181 Position of mirror lever Condenser

position.

360 14

200x 250mm 8x10” 0,9x 2,5x 380

380 H = REAR POSITION

Or V = FRONT POSITION

0,6x 1,3x 380 380 H = REAR POSITION

1,3x 2,8x 382 380 H = REAR POSITION 300

12

200x 250mm 8x10”

180x240mm 61/2 x 81/2 2,8x 4,0x 380

380 V = FRONT POSITION

0,4x 1,3x 380 380 V = FRONT POSITION 240

9 ½” 130x 180mm

5x7” 1,3x 5,0x 380 250 H = REAR POSITION

0,3x 1,lx 380 380 H = REAR POSITION

1,lx 3,0x 380 250 H = REAR POSITION 210

8 ½” 130x180mm

5x7”




7 1/8” 100x150mm 4 ¼ X 6 ½ “




6 100x125mm

4x5”


0,25 x 0,9 250 380 H = REAR POSITION 135

5 ¼” 85x100mm 3 ¼ x 4 ¼ “




4 1/8” 65x.90mm 2 ½ x 3 ½ “


80 31/

60x60mm 2 ¼ X 2 ¼ “ 3,8 x 21,0 X 180


60 2~/,

40x40mm 1 ½ X 1 ½ 5,0x 26,5x 160


50 2

24x36 35mm 6,7x 33,0x 160


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HORIZONTAL PROJECTION

Lens f =mm / inches

Negative size

mm / inches


minimum - maximum

Condenser combination

+LAZUCO 181 Position of mirror lever Condenser

position.

2,5x 9,0x 382 380

H = REAR POSITIONV = FRONT POSITION 360

14 200 x 250mm

8x10” 9,0x 21,0x 380


4,0x 5,3x 380 380 V = FRONT POSITION

300 12

200x 250mm 8x10”

180x240mm 6 ½ x 8 ½ “



9 ½” 130x180mm


210 8 ½”

130x180mm 5x7” 6,2x 33,0x 380


180 7”

100x150 4 ¼ x 6 ½ 7,5x 43,0x 250



6 100x125mm


135 5 1/4

85x100mm 3 ¼ x 4 ¼ “ 11,0x 47,0x 250


105 4 1/8

65x90mm 21/2” x 3 ½” 14,0 67,0x 180


80 3 1/8”

60x60mm 2 ¼ x 2 ¼ “ 21,0x 73,0x 180


60 2 1/8”

40x40mm 1 ½” x 1 ½” 23,0 x 84,5 x 180


50 2

24x36mm 35mm 33,0x 170,0x 160


On the left-hand side of the condenser head, when standing in front of the enlarger, there is a leaver. This lever manipulates the large mirror inside the condenser head; please make sure this lever is in the right position for the enlargement at hand. When nothing else in mentioned the condensers is installed in the head with the curved sides facing each other. When a point light lamp is used the condensers must be of the coated type.

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Condenser combinations for 5x7” Durst Condenser head.

DIFFUSED VERTICAL PROJECTION

Focal length of lens, mm (inches)

Nominal negative size, mm (inches)

Linear magnification Mm. Max.

Condenser comb.

Top Bottom

Minimum. diameter

of opal light source,

mm 1.7X 4.4Xxxx

240xxxxxx 240xxxxxx 240mm

9 ½ “ 130 X 180mm

5X7” 0.9X 1.7X 240 R

240

1.2X 5.3X 240 240 210mm

8 ½ ” 130X180mm

5X7” 0.7X 1.2X 240 R

240

3.2X 6.6X 240 200 180mm

7 1/8 ” 100X150mm 4 ¼ x 6 ½ “

0.5X 3.2X 240 240

110xxxxxx

1.0X 8.5X 240 200 150mm

6” 100X125mm

4X5” 0.4X 1.0X 240

240

1.0X 9.5X 240 160 135mm

5 ¼ “ 85X100mm 3 ¼ x 4 ¼ “

0.4X 1.0X 240 240

0.3X 2.4X 240 200 100mm

4” 65X90mm 2 ½ x 3 ½ “

2.4X 13.0X 240 130

80mm 31/8”

60X60mm 2 ¼ x 2 ¼ “ 0.6X 17.5X 200

130

90

60mm 2 3/8”

40X40mm 1 ½ x 1 ½ “ 2.9X 23.5X 130

85 50mm

2” 24X36 35mm 3.8X 28.5X 130

85

65

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DIFFUSED HORIZONTAL PROJECTION

Focal

length of lens, mm (inches)



Condenser comb.

Top Bottom

Minimum. diameter


mm 240mm 9 ½ “

130 X 180mm 5X7” 4.4x 21x 240

240 210mm 8 ½ ”

130X180mm 5X7” 5.3x 21x 240

240 H 180mm 7 1/8 ”

100X150mm 4 ¼ x 6 ½ “ 6.6x 26x 240

200 150mm

6” 100X125mm

4X5” 8.5x 30x 240 200

110

135mm 5 ¼ “

85X100mm 3 ¼ x 4 ¼ 9.5x 39x 200

160 100mm

4” 65X90mm 2 ½ x 3 ½ “ 12.0x 45x 200

130 80mm 31/8”

60X60mm 2 ¼ x 2 ¼ “ 17.5x 65x 160

130

90

60mm 2 3/8”

40X40mm 1 ½ x 1 ½ “ 23.5x 92x 130

85 50mm

2” 24X36 35mm 28.5x 102x 130

85

65

47


POINT-LIGHT VERTICAL PROJECTION




Mm. Max.

Condenser

combination

Top Bottom

2.2X 4.4X 240 PT 240T 240mm

9 ½ “

130X180 5X7”

0.9X 2.2X 240 PT 240PT

2.1X 5.3X 240 PT 240T 210mm

8 ½ „ 130X180

5X7“ 0.7X 2.1 240 PT

240 PT

1.2X 6.6X 240T 240T 180mm

7 1/8“ 100X150

4 ¼ x 6 ½ „ 0.5X 1.2X 240 RT

240T

2.5X 8.5X 240T 240T

0.8X 2.5X 240 T 240T

150mm 6“

100X125 4X5“

0.4X 0.8X 240 RI 240T

1.6X 9.5X 240T 200T

0.7X 1.6X 240T 240T

135mm 5 ¼ ”

85X100mm 4 ¼ x 4 ¼ ”

0.4X 0.7X 240 RT 240T

0.3X 0.6X 240 PT 240T

0.6X 2.0X 240 T 200T

2.0X 5.0X 240 T 130T

100mm 4”

65X90mm 2 ½ X 3 ½ “

5.0X 13.0X 200 T 130T

3.6X 17.5X 160T 110T

1.3X 3.6X 200T 130T

0.8X 1.3X 200 1 1601

80mm 3 1/8“

60X60mm 2 ¼ X 2 ¼“

0.6X 0.8X 240T 160T

4.0X 23.5X 130T 85T 60mm

2 3/8“ 40X40mm 1 ½ X 1 ½

2.9x 4.0x 130T 85T

50mm 2“

24X36 35mm 3.8X 28.5X 130T

85T

48

Condenser combinations for 5x7” Durst Condenser head. POINT-LIGHT HORIZONTAL PROJECTION

Focal length of

lens,

mm

(inch)




Top Bottom

240mm 9 ½ “

130X180mm 5X7” 4.4X 22.4X 240 PT

240 T

5.3X 8.2X 240 PT 240 T 210mm

8 ½ „ 130X180mm

5X7“ 8.2X 20.5x 240 PT

240 HT

6.6X 13.5X 240 T 240 T 180mm

7 ½“ 100X150mm 4 ¼ X 6 ½“

13.5X 27.2X 240 T 240 HT

150mm 6“

100X125mm 4X5“ 8.5X 32.5X 240 T

200 T 135mm

5 ¼“ 85X100mm 31/4X41/4 9.5X 42.0X 240 HT

200 T 105mm 4 1/8“

65X90mm 21/2X31/2 11.8X 47.0X 240 T

130 T 100mm

4“ 65X90mm

2 ½ X 3 ½ “ 13.0X 45.0X 240 HT 130 T

80mm 3 1/8”

60X60mm 21/4X21/4 17.5X 75.0X 160 T

130 T

60mm 2 3/8“

40X40mm 1 ½ X 1 ½“ 23.5X 104.0X

130 T 110 T

50mm 2”

24X36mm 35mm 28.5X 116.0X 130 T

110 T

49

MANUAL FOR DeVere CONDENSER SYSTEM, Available from DURST-PRO-USA, Inc.

NEGATIVE SIZE RECOMMENDED LENSES CONDENSER COMBINATIONS

11x14" 480mm Rodagon, 300mm

Rodenstock Geragon, 270mm Rodenstock Geragon.

4 elements, set #1 and set#2.

Set#1 condenser 10x10", 8x10" and

18x24cm 480mm, 360, 300mm or 240mm 4 elements, set #1 and set#2

5x7", 13x18cm and 6x17cm 240mm, 210mm and 180mm

4 elements, set #1 and set#2 PLUS

240mm supplementary element

4x5", 9x12cm, 6x12cm 210mm, 180mm and 150mm 4 elements, set #1 and set#2

PLUS 180mm supplementary element

6x9cm and 6x7cm 150mm, 135mm and 105mm


180mm supplementary element and thick spacer in negative holder.

6x6, 4.5x6 and 4x4cm 105, 90mm and 80mm.


180mm supplementary element and thick spacer in negative holder.

35mm 60mm lenses


180mm supplementary element PLUS

one thick and one thin spacer in negative holder

Please notice: When using a condenser system the critical components are the enlarging lens and the condenser lenses. How those two items are combined determine the lamp position. The size of the negative play no role in the equation and has no influence on the result. Any size negative can be used with any correct combination of enlarging lens and condenser lens. Example #1, a "small crop" crop of from an 10x10" negative can be printed with any focal length lens having a circle of coverage large enough to cover the diagonal of the crop as long as the correct condenser combination for that particular lens is used. Example #2, a 35mm lens can be printed with any lens having a circle of coverage large enough to cover as long as the correct condenser combination for that particular lens is used.

This situation is ONLY limited by physical limitations of the equipment in use

50

DeVere Condenser Light source adjustments: Three adjustments are provided for centering the lamp on the optical axis. Two of the adjusting knobs are on the underside of the lamp house and one on the lower right-hand side of the lamp house. The larger of the two knobs on the underside adjusts the lamp in the vertical plane and the small knob, to the right of the large knob, imparts a rotational movement whereby the lamp filament can be squared with the aperture. The adjusting knob on the right-hand side provides lateral movement of the lamp at right angles to the optical axis. To adjust proceed as follows: 1. Remove the negative holder from the machine and fit an 8xlO” (203mm x 254mm) frame.

Install a negative, any negative. 2. See that the masking leaves are well clear of the 8xlO” aperture. The 2 hand wheels on the

left-hand side of the machine can adjust the position of the masking blades. Some machines delivered by DURST-PRO-USA, Inc. have been retrofitted with the more advanced Durst negative holder. When this modification is made the masking blades has been removed to make space for the thicker negative holder.

3. Adjust the negative carrier rise and fall hand wheel until the scale at the right-hand side of the

negative stage is at zero setting. This centralizes the negative carrier in the vertical plane. 4. Insert the negative holder in the negative stage until the ends~ are flush with the negative stage

casting. This ensures the negative carrier is centralized in the horizontal plane. 5. Install a 360mm focal length lens to a on the lens stage. Set the lens to a wide aperture. Switch

on the Condenser light. 6. (DeVere use a bayonet type fitting for their lens boards, high end machines delivered by

DURST-PRO-USA, Inc have been retrofitted with a Durst lens board adapter.) 7. Release the negative stage locking lever, the lens stage drive and the condenser housing drive.

Make sure that the negative stage and the condenser housing is properly connected. 8. Adjust the positions of the negative and lens stages on the optical bench to give approximate size

and sharp focus. Now engage the negative stage locking lever, the lens stage drive and the condenser house drive in order to maintain sharp focus at the given size. REMOVE THE NEGATIVE!.

9. Release the lamp house runner locking lever and move the unit along it’s expandable track.. It

will be seen that the image, on the baseboard, appears to be of a circular nature with a dark fringe. Find the position where the illumination appears fairly even. Lock the lamp house runner in this position and stop the lens aperture diaphragm down until a white circle with a blue surround will become apparent. It is likely that this circle will not be in the centre of the projected image. Using the three adjustments described at the beginning of this paragraph. Adjust the position of the lamp until it is perfectly centered in relation to the negative and optical systems It is possible that there will be a slight cut-off of the projected image.

10. If the cut-off is the same at the four edges of the image adjust the position of the lamp-house on

it’s track until a perfectly clean, white illuminated area is obtained.

51

11. I

ltrithC

The two set condensers installed. T

f the cut-off is not the same at the four edges iens mounts need slight adjustment. Ease the Cohe lamp house bellows to adjust in a rotating ight-hand side of the condenser housing to mncrements from right to left. If it is necessary to he two screws slightly, open the housing door and Repeat adjustments until the required pondenser mount adjusting/locating screw under

Condenser access door

52

he condensers are quite impressive.

t is possible that the position of the condenser ndenser mount adjusting/locating screw under

movement. Use the 2 adjusting screws on the ove the condenser mount assemblies in small move the mounts in the opposite direction, ease on the opposite side and move the mounts by ositions are obtained Finally ensure that the the bellows is firmly tightened

positioning screws.

SUPPLEMENTARY C0NDENSER LENSES and NEGATIVE CARRIERS The table of recommended lens and condenser combinations shows that the standard 4-element condenser assembly will cover negative format sizes from 11xl4” down to 10x10”. For smaller negative formats the use of supplementary lenses is recommended. Two supplementary (condenser) lenses with diameters off 180mm and 240mm are available for this purpose. The supplementary lenses are mounted on metal plates which locate in the recess in the negative stage in the same manner as the loose plate used when the standard condenser assembly only is being used. TloTe FnmT6t JWM

he mounting plate should be inserted in the rens facing the condenser housing When theperating position and secured to the negative she convex surface of the supplementary lens flement of the standard 4-element assembly

or negative sizes 6x9cm and below, in addecessary to position the negative further awayost intense part of the light beam. his is achieved by the use of either a circula0mm version, or by the use of a spacer betweeypes are available from DURST-PRO-USA, In

ens J. Jensen orld Images Inc ay 30, 2002.

Snap bracket. Recess for insertion of plates w. accessory condensers. Bottom brackets.

ecess with the convex surface of the supplementary condenser/lamp-house assembly is moved into its tage. its neatly within the concave surface of the foremost

ition to the use of supplementary lenses it will be from the condenser system in order to keep it in the

r negative holder adapter, available in a 30mm and n the negative stage and the condenser housing. Both c.

53

Projection information for DURST Horizontal enlargers. This table is intended for calculating track length for horizontal Durst HL2500 series enlargers. FOCAL

LENGTH 360MM RODAGON 300mm RODAGON 240mm RODAGON

Format A B C D A B C D A B C D

8x10 NA NA NA NA 25 46.5 85.5 23.5 18.5 37 76 20.5

12x16” 35.5 57 95 22 30 49 88 21.5 24.5 40 79 17.5

20x24” 48.5 67.5 106 20 40 57 96 19 31.5 45.5 84.5 15.5

30x40” 70.5 86.5 125 18 58 73 104 17 47 59 98 14.5

40x50” 85.5 102 139 17.5 71 85 124 16.5 57 69 108 14

50x60” 98.5 114.5 150 17 82 96.5 135.5 16 66 78.5 117.5 13.5

80x100” 150 165 217 16 124.5 138 177 15.5 103 114.5 143.5 13 A = distance from baseboard / vacuum wall to lens nodal point (Nodal point is approx middle of lens) B = distance from baseboard / vacuum wall to negative plane C = distance from baseboard / vacuum wall to the rear end of the enlarger. D = bellows extension. also B = distance from negative to baseboard C = total length of room or tracks. (If measurements are needed for Durst L184/1840 please subtract approx. 12” from column “C”. Max print size with 300mm lens is 30x40” from a full neg.) These measurements may vary considerably for a DeVere horizontal enlarger because it is possible to move the negative stage up to 24 inches on BOTH sides of the center of the optical bench. This movement is not possible on a Durst enlarger. The measurements above assumes the negative stage placed at the very front, as is the case on a Durst horizontal enlarger, and as such the tracks can be up to 30 inches shorter than indicated when a DeVere horizontal enlarger is used.. All measurements are in INCHES. Measurements are approximate. Rodenstock recommend a 240mm lens used at 4X enlargement Rodenstock recommend a 300mm lens used at 4X enlargement Rodenstock recommend a 360mm lens used at 2.5X enlargement Using the lenses outside these recommendations will not guarantee optimum sharpness and resolution. There are special lenses for the 1:1 area (APO type lenses, APO Rodagon, APO Ronar and other special lenses) and for the area above 10X enlargements (G type lenses).NA = needs extended lens board and/or bellows extension if a 360mm lens is used for 1:1 printing.

54


DIFFUSED VERTICAL PROJECTION




Condenser comb.

Top Bottom

Minimum. diameter


mm 1.7X 4.4Xxxx

240xxxxxx 240xxxxxx 240mm

9 ½ “ 130 X 180mm

5X7” 0.9X 1.7X 240 R

240

1.2X 5.3X 240 240 210mm

8 ½ ” 130X180mm

5X7” 0.7X 1.2X 240 R

240

3.2X 6.6X 240 200 180mm

7 1/8 ” 100X150mm 4 ¼ x 6 ½ “

0.5X 3.2X 240 240

110xxxxxx

1.0X 8.5X 240 200 150mm

6” 100X125mm

4X5” 0.4X 1.0X 240

240

1.0X 9.5X 240 160 135mm

5 ¼ “ 85X100mm 3 ¼ x 4 ¼ “

0.4X 1.0X 240 240

0.3X 2.4X 240 200 100mm

4” 65X90mm 2 ½ x 3 ½ “

2.4X 13.0X 240 130

80mm 31/8”

60X60mm 2 ¼ x 2 ¼ “ 0.6X 17.5X 200

130

90

60mm 2 3/8”

40X40mm 1 ½ x 1 ½ “ 2.9X 23.5X 130

85 50mm

2” 24X36 35mm 3.8X 28.5X 130

85

65

55


DIFFUSED HORIZONTAL PROJECTION

Focal

length of lens, mm (inches)



Condenser comb.

Top Bottom

Minimum. diameter


mm 240mm 9 ½ “

130 X 180mm 5X7” 4.4x 21x 240

240 210mm 8 ½ ”

130X180mm 5X7” 5.3x 21x 240

240 H 180mm 7 1/8 ”

100X150mm 4 ¼ x 6 ½ “ 6.6x 26x 240

200 150mm

6” 100X125mm

4X5” 8.5x 30x 240 200

110

135mm 5 ¼ “

85X100mm 3 ¼ x 4 ¼ 9.5x 39x 200

160 100mm

4” 65X90mm 2 ½ x 3 ½ “ 12.0x 45x 200

130 80mm 31/8”

60X60mm 2 ¼ x 2 ¼ “ 17.5x 65x 160

130

90

60mm 2 3/8”

40X40mm 1 ½ x 1 ½ “ 23.5x 92x 130

85 50mm

2” 24X36 35mm 28.5x 102x 130

85

65

56


POINT-LIGHT VERTICAL PROJECTION




Mm. Max.

Condenser

combination

Top Bottom

2.2X 4.4X 240 PT 240T 240mm

9 ½ “

130X180 5X7”

0.9X 2.2X 240 PT 240PT

2.1X 5.3X 240 PT 240T 210mm

8 ½ „ 130X180

5X7“ 0.7X 2.1 240 PT

240 PT

1.2X 6.6X 240T 240T 180mm

7 1/8“ 100X150

4 ¼ x 6 ½ „ 0.5X 1.2X 240 RT

240T

2.5X 8.5X 240T 240T

0.8X 2.5X 240 T 240T

150mm 6“

100X125 4X5“

0.4X 0.8X 240 RI 240T

1.6X 9.5X 240T 200T

0.7X 1.6X 240T 240T

135mm 5 ¼ ”

85X100mm 4 ¼ x 4 ¼ ”

0.4X 0.7X 240 RT 240T

0.3X 0.6X 240 PT 240T

0.6X 2.0X 240 T 200T

2.0X 5.0X 240 T 130T

100mm 4”

65X90mm 2 ½ X 3 ½ “

5.0X 13.0X 200 T 130T

3.6X 17.5X 160T 110T

1.3X 3.6X 200T 130T

0.8X 1.3X 200 1 1601

80mm 3 1/8“

60X60mm 2 ¼ X 2 ¼“

0.6X 0.8X 240T 160T

4.0X 23.5X 130T 85T 60mm

2 3/8“ 40X40mm 1 ½ X 1 ½

2.9x 4.0x 130T 85T

50mm 2“

24X36 35mm 3.8X 28.5X 130T

85T

57

Condenser combinations for 5x7” Durst Condenser head. POINT-LIGHT HORIZONTAL PROJECTION

Focal length of

lens,

mm

(inch)




Top Bottom

240mm 9 ½ “

130X180mm 5X7” 4.4X 22.4X 240 PT

240 T

5.3X 8.2X 240 PT 240 T 210mm

8 ½ „ 130X180mm

5X7“ 8.2X 20.5x 240 PT

240 HT

6.6X 13.5X 240 T 240 T 180mm

7 ½“ 100X150mm 4 ¼ X 6 ½“

13.5X 27.2X 240 T 240 HT

150mm 6“

100X125mm 4X5“ 8.5X 32.5X 240 T

200 T 135mm

5 ¼“ 85X100mm 31/4X41/4 9.5X 42.0X 240 HT

200 T 105mm 4 1/8“

65X90mm 21/2X31/2 11.8X 47.0X 240 T

130 T 100mm

4“ 65X90mm

2 ½ X 3 ½ “ 13.0X 45.0X 240 HT 130 T

80mm 3 1/8”

60X60mm 21/4X21/4 17.5X 75.0X 160 T

130 T

60mm 2 3/8“

40X40mm 1 ½ X 1 ½“ 23.5X 104.0X

130 T 110 T

50mm 2”

24X36mm 35mm 28.5X 116.0X 130 T

110 T

58


VERTICAL PROJECTION

Lens f = mm /

inches

Negative size mm / inches


minimum maximum

Condenser Combination

+LAZUC0 181 Position of mirror lever Condenser

position.

360 14

200x 250mm 8x10” 0,9x 2,5x 380


Or V = FRONT POSITION



12

200x 250mm 8x10”

180x240mm 61/2 x 81/2 2,8x 4,0x 380


0,4x 1,3x 380 380 V = FRONT POSITION 240

9 ½” 130x 180mm


0,3x 1,lx 380 380 H = REAR POSITION

1,lx 3,0x 380 250 H = REAR POSITION 210

8 ½” 130x180mm

5x7”




7 1/8” 100x150mm 4 ¼ X 6 ½ “




6 100x125mm

4x5”


0,25 x 0,9 250 380 H = REAR POSITION 135

5 ¼” 85x100mm 3 ¼ x 4 ¼ “




4 1/8” 65x.90mm 2 ½ x 3 ½ “


80 31/

60x60mm 2 ¼ X 2 ¼ “ 3,8 x 21,0 X 180


60 2~/,

40x40mm 1 ½ X 1 ½ 5,0x 26,5x 160


50 2

24x36 35mm 6,7x 33,0x 160


59


HORIZONTAL PROJECTION

Lens f =mm / inches

Negative size

mm / inches


minimum - maximum


+LAZUCO 181 Position of mirror lever Condenser

position.

2,5x 9,0x 382 380

H = REAR POSITIONV = FRONT POSITION 360

14 200 x 250mm

8x10” 9,0x 21,0x 380



300 12

200x 250mm 8x10”

180x240mm 6 ½ x 8 ½ “



9 ½” 130x180mm


210 8 ½”

130x180mm 5x7” 6,2x 33,0x 380


180 7”

100x150 4 ¼ x 6 ½ 7,5x 43,0x 250



6 100x125mm


135 5 1/4

85x100mm 3 ¼ x 4 ¼ “ 11,0x 47,0x 250


105 4 1/8

65x90mm 21/2” x 3 ½” 14,0 67,0x 180


80 3 1/8”

60x60mm 2 ¼ x 2 ¼ “ 21,0x 73,0x 180


60 2 1/8”

40x40mm 1 ½” x 1 ½” 23,0 x 84,5 x 180


50 2

24x36mm 35mm 33,0x 170,0x 160


On the left-hand side of the condenser head, when standing in front of the enlarger, there is a leaver. This lever manipulates the large mirror inside the condenser head; please make sure this lever is in the right position for the enlargement at hand. When nothing else in mentioned the condensers is installed in the head with the curved sides facing each other. When a point light lamp is used the condensers must be of the coated type.

60

collimated lights vs. diffused light - durst-pro-usa

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