instructions to define the nodal point - · pdf fileinstructions to define the nodal point ......

© by Seitz Phototechnik AG, Hauptstr. 14, 8512 Lustdorf, Switzerland, Phone: +41 52 376 3353, Fax: +41 52 376 3305, [email protected], www.roundshot.chTechnical changes reserved, Released: 1.2005

Instructions to Define the Nodal Point

Roundshot Super 220 VRSoftware Release 4.0 and higher


1. Introduction

1.1 What is a nodal point?

The term „nodal point“ defines the optical centres of a lens where the incominglight is bundled in the optical axis.

1.2 What is the significance of the nodal point for panoramic photography?

For rotational panoramic photography of up to 360° the camera head with the lens rotatesaround a vertical axis. For optimum sharpness the nodal point needs to be exactly at the centreof this axis. If the nodal point is not situated exactly at the centre of the rotation axis, a so-calledparallax effect occurs. When rotating the camera the distances between vertical lines changeand sharpness as well as depth of field decreases.

Second nodal point (H)First nodal point (H’)

Good nodal point: Bad nodal point (parallax effect):

Film plane

Focal length(in mm)

The first (front) nodal point is theposition on the optical axis of a lens where the entering raycrosses the optical axis.

The second (rear) nodal point is theposition on the optical axis of a lenswhere the departing ray crosses theoptical axis.

The distance from the second nodal point to the focal point (film plane) is the focal length.


2. Procedure to define the nodal point for the Roundshot Super 220 VR with Software Release 4.0 and higher

The Roundshot Super 220 VR camera makes it possible to fit lenses of 13mm up to 1,000 focallength of a variety of manufacturers. The nodal point of these lenses is always different. For optimum depth of field the camera head is moved forward and backward on the optical benchto centre the nodal point of the lens in the rotation axis.

Optical bench(with scale for b-values)

Movement of camera head

Up to Software Release 3.97 the second nodal point was the reference and the b-value was calculated using a mathematical formula.

Camera tests have revealed that rotating in the first nodal point allows an even better sharpnessand depth of field. That is why – with Software Release 4.0 and higher – the first nodal point istaken as a reference. This nodal point is defined empirically / optically.


2.1 Defining the nodal point for the Roundshot Super 220 VR withSoftware Release 4.0 and higher

Good nodal point:Distance unchanged after rotation

Bad nodal point:Distance changed after rotation

Define two points in space that lie behind each other. Ideally takevertical lines (such as houses, poles, pillars etc.) at a distance of about 2m and 6m.

Focus at 4m.

Position the Super camera in such a way that the two lines areexactly behind each other. The line should be either on the very leftor on the very right of the viewfinder.

Rotate the camera head and observe in the viewfinder (ideally withmagnifying glass) how the two lines behave.

If the two lines are still exactly behind each other, then the nodalpoint is found.

If not, change the position of the camera on the optical bench(forward or backward) and repeat the procedure until the lines areexactly aligned.


2.2 Read the b-value and enter it in the Super SoftwareExample: Nikkor 28mm PC Shift f/3,5

Read the b-value on the scaleof the optical bench. B = 72

Open the lens list of the Roundshot Super Software.

Enter the effective focal length* of your lens in the list (for example 28.6mm) and press button„D“ to save.

* A list of effective focal lengths and a simple empirical approach to determine effective focal length is given in the Appendix; this data has beencollected from manufacturers data sheets (where available) and from Seitz research; due to the wide variety of available lenses and thesometimes difficult access to lens data no warranty can be given as to the completeness and exhaustiveness of data


Enter now the h-value. This value is calculated as follows:

=h-value(mm)

43.4

b-value(mm)

72.0

Effective focal length(mm)

28.6

The h-value is a correction value to bring the nodal point exactly into the rotation axis.

Press button „D“ to save.


Open the list of distance values, enter the focusing distance and press button „D“ to save.

As a result the optimum b-value is displayed again.

The optimum nodal point for your lens is now saved in the software and can be accessed anytime again.


Repeat this procedure for all of your lenses and check the sharpness using test film.

At closer distances (for example 1m instead of infinite) the lens has a longer effective focaldistance. This means that the b-value is increased by this difference (for example 29.4mm whenfocusing at 1m instead of 28.6mm at infinite distance for Nikkor 28mm PC Shift f/3,5). Henceslightly different b-values are obtained for different distances.

However, in reality these differences are not significant and can be ignored. A tolerance of +/-1mm on the optical bench cannot be detected by the human eye when defining the nodalpoint optically and leads to identical depth of field.

When using very wide angle lenses it is possible that the camera head moves back to the veryend of the optical bench and that the control unit and the battery appear in the image. This canbe solved by detaching control unit and battery with an external cable (article number 3084 and 3085) from the camera engine.

The b-values for the saved lenses with their respective distance settings can be accessed in theSoftware at all times. The Super Software can accomodate up to 20 lenses. When changinglenses these values can be retrieved and the optimum nodal point can be set on the opticalbench.

We are convinced that this new procedure to define the nodal point will produce very good results and wish you continued success and fun with your Roundshot Super 220 VR.


Appendix A: Lens Lists

The following tables are worksheets for your own selection of lenses.

Wherever available we have listed the effective focal length. This data has been collected frommanufacturers data sheets (where available) and from Seitz research; due to the wide variety of available lenses and the sometimes difficult access to lens data no warranty can be given as to the completeness and exhaustiveness of data.

You can fill in your own values in the colums „B-Value“ and „H-Value“ for future reference.


Nikon Nikkor

Lens Focal length Minimum Effective focal length B value H valueaperture "f" determined optically H = B - f

mm f mm mm mmNikkor 13 5,6 13.3 Nikkor 15 3,5 15.4 Nikkor 18 3,5 18.1 Nikkor 20 2,8 20.3 Nikkor 24 2,0 24.5 Nikkor 24 2,8 24.6 Nikkor 28 2,0 28.4 Nikkor 28 2,8 28.7 PC Nikkor 28 3,5 28.6 Nikkor 35 1,4 35.8 Nikkor 35 2,0 35.7 Nikkor 35 2,8 35.4 PC Nikkor 35 2,8 36.4 Nikkor 50 1,2 51.6 Nikkor 50 1,4 51.6 Nikkor 50 1,8 51.5 Micro Nikkor 55 2,8 55.0 Noct Nikkor 58 1,2 57.9 Nikkor 85 1,4 84.9 Nikkor 85 2,0 85.0 Nikkor 105 1,8 104.9 Nikkor 105 2,5 105.0 Micro Nikkor 105 2,8 105.4 Micro Nikkor UV 105 2,8 105.1 Nikkor 135 2,0 135.1 Nikkor 135 2,8 135.1 Nikkor 135 3,5 135.1 Nikkor 180 2,8 180.2 Nikkor IF-ED 200 2,0 199.4 Nikkor 200 4,0 199.5 Micro Nikkor 200 4,0 201.5 Nikkor IF 300 4,5 299.9 Nikkor IF 400 2,8 400.2 Nikkor IF 400 3,5 400.1 Nikkor IF 400 5,6 400.1 Nikkor IF 500 4,0 495.5 Reflex Nikkor 500 8,0 520.0 Nikkor IF 600 4,0 602.0 Nikkor IF 600 5,6 601.0 Nikkor IF 800 5,6 801.5 Reflex Nikkor 1000 11,0 999.7


Nikon AF


mm f mm mm mmAF Nikkor D 18 2,8 18.5 AF Nikkor D 20 2,8 20.4 AF Nikkor D 24 2,8 24.2 AF Nikkor D 28 1,4 28.5 AF Nikkor D 28 2,8 28.8 AF Nikkor 35 2,0 35.9 AF Nikkor 50 1,4 51.6 AF Nikkor 50 1,8 51.6 AF Micro Nikkor D 60 2,8 60.1 AF Nikkor 85 1,8 84.8 AF DC Nikkor D 105 2,0 103.4 AF Nikkor D 105 2,8 105.3 AF DC Nikkor 135 2,0 134.6 AF Nikkor ED 180 2,8 180.0 AF Micro Nikkor D 200 4,0 201.3 AF Nikkor ED 300 2,8 299.8 AF I Nikkor ED 300 2,8 299.8 AF Nikkor ED 300 4,0 299.4


Leica


mm f mm mm mmSuper Elmarit R 15 3,5 15.4 Elmarit R 19 2,8 19.4 Super Angulon 21 4,0 21.7 Elmarit R 24 2,8 24.3 Elmarit R 28 2,8 28.5 Super Angulon Shift 28 2,0 29.2 Summilux R 35 1,4 36.0 Summicron R 35 1,8 35.2 Elmarit R 35 2,8 35.2 PA Curtagon R 35 1,8 35.2 Summilux R 50 2,0 52.4 Summicron R 50 2,8 52.3 Macro Elmarit R 60 2,0 61.4 Summilux R 80 2,8 80.0 Summicron R 90 4,0 89.9 Elmarit R 90 2,8 91.0 Apo Macro Elmarit R 100 2,8 100.2 Macro Elmarit R 100 4,0 100.1 Elmarit R 135 2,8 135.1 Elmarit R 180 2,8 179.6 Apo Telyt R 180 3,4 181.7 Elmarit R 180 4,0 179.7 Tolyt R 250 2,8 251.8 Telyt R 280 2,8 279.2


Contax Zeiss


mm f mm mm mmDistagon T 15 3,5 15.4 Distagon T 18 4,0 18.6 Distagon T 21 2,8 21.0 Distagon T 25 2,8 25.9 Distagon T 28 2,8 28.5 Distagon T 35 1,4 36.5 Distagon T 35 2,8 35.9 PC Distagon T 35 2,8 35.2 Tessar T 45 2,8 46.5 Planar T 50 1,4 51.8 Planar T 50 1,7 51.9 Makro Planar T 60 2,8 61.7 Planar T 85 1,4 84.8 Planar T 100 2,0 99.9 Makro Planar T 100 2,8 100.0 Sonnar T 135 2,8 134.1 Sonnar T 180 2,8 178.1 Aposonnar T 200 2,0 199.9 Tele Apotessar T 300 2,8 300.6 Tele Tessar T 300 4,0 300.0 Mirotar T 500 4,5 504.5 Mirotar T 500 8,0 500.0 Mirotar T 1,000 5,6 1,020.6


Sigma


mm f mm mm mmAF / MF 14 3,5 14.5 AF 18 3,5 18.6

14 2,8 14.5


Zeiss Hasselblad


mm f mm mm mmDistagon 40 4,0 40.9 Distagon 50 2,8 51.7 Distagon 50 4,0 52.0 Distagon 60 3,5 60.2 Planar 80 2,8 80.5 Planar 100 3,5 100.3 UV Sonnar 105 4,3 107.5 Planar 110 2,0 110.8 Makro Planar 120 4,0 120.9 Makro Planar 135 5,6 137.1 Sonnar 150 2,8 151.1 Sonnar 150 4,0 151.2 Sonnar 180 4,0 179.4 Tele Tessar 250 4,0 246.3 Sonnar 250 5,6 248.4 Sonnar Superachromat 250 5,6 248.7 Tele Tessar 350 4,0 350.3 Tele Tessar 350 5,6 341.2 Tele Apotessar 500 8,0 499.3


Large format


mm f mm mm mmRodenstock Apo Grandagon 35 4,0 40.9 Schneider Super Angulon 47 2,8 51.7 Schneider Super Angulon XL 47 4,0 52.0 Schneider Super Angulon XL 58 3,5 60.2 Schneider Super Angulon 65 2,8 80.5 Schneider Super Angulon XL 72 3,5 100.3 Schneider Super Angulon 75 4,3 107.5 Schneider Super Angulon XL 90 2,0 110.8 Schneider Apo Symar 100 4,0 120.9 Schneider Apo Symar 120 5,6 137.1 Schneider Apo Symar 135 2,8 151.1 Schneider Apo Symar 150 4,0 151.2


Pentax 67


mm f mm mm mmPentax 67 45 4,0 46.2 Pentax 67 55 4,0 56.0 Pentax 67 75 4,5Pentax 67 Shift 75 4,5Pentax 67 90 2,8Pentax 67 105 2,4 105.0 Pentax 67 Soft 120 3,5Pentax 67 Macro 135 4,0Pentax 67 165 2,8Pentax 67 LS 165 4,0Pentax 67 200 4,0 199.9 Pentax 67 300 4,0Pentax 67 M 400 4,0Pentax 67 500 5,6Pentax 67 600 4,0Pentax 67 M 800 6.7Takumar 67 800 4,0Relfex 67 Takumar 1,000 8,0


Rollei 3000


mm f mm mm mmDistagon HFT 15 3,5 15.4 F-Distagon 16 2,8 15.8 Distagon T 18 4,0 18.6 Ro 20 2,8 20.5 VLP 21 4,0 21.6 Distagon T 25 2,8 25.9 Distagon HFT 28 2,8 28.8 VLP 28 2,8 28.0 Distagon HFT 35 1,4 36.5 Angulon 35 2,8 35.5 Rolleinar 35 2,8 35.0 Sonnar 40 2,8Samsung 50 1,4 51.5 Planar 50 1,4 50.9 Planar neu 50 1,4 51.8 Planar 50 1,8 51.8 SL-Xenon 50 1,8 51.6 - 52.9Rolleinar MC 55 1,4 54.7 S-Planar 60 2,8 61.7 Planar HFT 85 1,4 84.8 Sonnar 85 2,8 84.9 VLP 85 2,8 86.1 VLP 105 2,8 105.0 Rolleinar 135 2,8 134.9 Sonnar 135 2,8 135.0 Tele-Tessar 135 4,0 132.6 Tele-Tessar 200 3,5 194.0 Tele-Tessar 200 4,0 193.7 Tele-Tessar 300 4,0 300.0 Mirotar 500 4,5 504.5PC-Curtagon 35 4,0 35.2


Mamiya 645


mm f mm mm mmMamiya C 24 4,0 24.0 Mamiya C 35 3,5 35.8 Mamiya C 45 2,8 46.0 Mamiya Shift C 50 4,0 51.0 Mamiya C 55 2,8 55.5 Mamiya C 80 1,9 80.0 Mamiya C 80 2,8 80.1 Mamiya Macro C 80 4,0 80.1 Mamiya Macro A 120 4,0 117.0 Mamiya A 150 2,8 147.3 Mamiya C 150 3,5 145.9 Mamiya A 200 2,8 195.3 Mamiya C 210 4,0 210.3 Mamiya A 300 2,8 292.4 Mamiya C 300 5,6 299.7 Mamiya A 500 4,5 493.7 Mamiya C 500 5,6 500.0


Appendix B: Practical Approach to Determine the Effective Focal Length

Not all lens data is public. That‘s why – for some lenses - your own testing is required.This is a simple and very practical test that has been developed by one of our customers and that will give you very precise measurements.

Step 1: Set up a square table at a distance of a few metres on a wall (exactly 90° angle to camera). On the table draw a cross (for example, exactly 1m vertical, 1m horizontal, bigger forwide-angle lenses):

1m

1m

Step 2: Determine the nodal point of the lens optically (as described previously)

Step 3: Mount the Super camera on a tripod and centre the optical axis exactly at the centre of the cross. Focus on infinite distance (otherwise the effective focal length will deviate). Enter theeffective focal length in the Super Software, starting for example with f=28.0

0


Step 4: Complete a series of test images, each time increasing the effective focal length in theSuper Software. Plot the f value on the table. The Software will adjust image length and aspectratio:

1m

1m

f=28.0

1m

1m

f=28.1

1m

1m

f=28.2

1m

1m

F=29.0…

Step 5: Complete a series of test images, each time decreasing the effective focal length in theSuper Software. Plot the f value on the table. The Software will adjust image length and aspectratio:

1m

1m

f=28.0

1m

1m

f=27.9

1m

1m

f=27.8

1m

1m

f=27.0…

f=28.0 f=28.1 f=28.2 f=29.0

f=28.0 f=27.9 f=27.8 f=27.0


Step 6: Develop the film and evaluate the results

1m

1m

1m

1m Take the first image (f=28.0) and tilt itby 90°. The now horizontal line on thefilm is exactly 1m and is the referencevalue.

1m

1m

1m

1m

f=27.0 ..f=29.0

Compare the horizontal 1m line withthe vertical 1m line (tilted).The one test square that matchesexactly the 1m line is your effectivefocal length.

Cut the images (film).

Use a lightbox and lay your test images over the reference image (first, tilted image).

instructions to define the nodal point - · pdf fileinstructions to define the nodal point ......

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