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Parts and working of a telescopic zoom camera

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Parts and working of a telescopic zoom camera

Basics of capturing a picture

Light enters a dark box through a small hole and creates an inverted image on the wall opposite the hole.

Role of a camera in capturing pictures A still camera is an optical device which creates a single image of an object or scene, and records it on an electronic sensor or photographic film.

All cameras use the same basic design: light enters an enclosed box through a converging lens and an image is recorded on a light-sensitive medium.

A shutter mechanism controls the length of time that light can enter the camera.

A movie camera or a video camera operates similarly to a still camera, except it records a series of static images in rapid succession, commonly at a rate of 24 frames per second.

When the images are combined and displayed in order, the illusion of motion is achieved.

Camera buttons and controlsLens AlignmentFlash Pop Up ButtonLens ReleaseDepth of Field previewLens contactsMirrorGripShutter Release ButtonFocus Assist BeamPop Up Flash

ViewfinderDiopterAdjustmentRubberEye-cupJoystick DialExposure Lock/Zoom ButtonFocus Point Selector/Zoom ButtonWrite Indication LightJog Dial and Set buttonOn/Off ButtonErase Button11,12,13,14- UI buttons12-LCD screen

Light for LCD DisplayAuto focus/white balanceDrive/ISOShutter ButtonTop DialMetering/Flash CompensationLCD ScreenHotshoeExposure control Dial Flash

Main functional partsAperture ring-This part of the DSLR is used to manually select the desired aperture.

Dust removal system-These systems work by shaking the sensor very rapidly in order remove the dust particles.

Focus ring-The focus ring is used to manually let you have a control over the focus.

Live view-. This is especially useful for photographers using a tripod or working at odd angles.

Mount-The mount is the physical connection between the lens and the camera body.

Prime lens-These lenses are the ones which are fixed within the camera, which offer the best image quality.

Sensor-Used to capture incoming light.

Zoom lens-Unlike prime lenses, a zoom lens can cover a range of focal lengths.

Viewfinder-A viewfinder will display the various focus areas superimposed over the image

Zoom ring-This is the ring that one adjusts to manually control the zoom of your subject.

Zoom lens

A zoom lens is a mechanical assembly of lens elements for which the focal length (and thus angle of view) can be varied, as opposed to a fixed focal length (FFL) lens or prime lens.

Zoom lenses are often described by the ratio of their longest to shortest focal lengths.

A zoom lens with focal lengths ranging from 100mm to 400mm may be described as a 4:1 or "4" zoom.

This ranges up to 19 in SLR camera lenses, 83 in amateur digital cameras and can be as high as 300 in professional television cameras.

But photographic zoom lenses beyond 3 cannot generally produce imaging quality on par withprime lenses.

It features very complicated internal construction.

Principle

A simple zoom lens system

The three lenses of the afocal system areL1,L2,L3.

LensL3is fixed, but lensesL1andL2can be moved axially in a particular non-linear relationship, changing the overall focal length of the system.

While the negative lensL2moves from the front to the back of the lens, the lensL1moves forward and then backward in a parabolic arc.

In doing so, the overall angular magnification of the system varies, changing the effective focal length of the complete zoom lens.

The two fundamental parameters of an optical lens are the focal length and the maximum aperture.

The lens' focal length determines the magnification of the image projected onto the image plane, and the aperture the light intensity of that image.

Focal lengths are usually specified in millimetres (mm).

28 mm lens50 mm lens70 mm lens210 mm lens

With a large pinhole, the image spot is large, resulting in a blurry image.With a small pinhole, light is reduced and diffraction prevents the image spot from getting arbitrarily small.With a simple lens, much more light can be brought into sharp focus.

PartsThe mechanical movement of the optics within this zoom lens can be broken down into three independently moving groups of optical elements and one stationary group of optical elements.the focus group,the variator group,the compensator group, andthe master group.

Functions of various partsThe focus group moves forward or backward as necessary for focusing the lens.

Thevariator groupof lens elements, like its name implies, varies the magnification power of the focus group.

The variator group alone isn't enough to achieve a true zoom function and maintain focus.

The compensator groupof lens elements maintains proper focus when zooming a true zoom lens.

True zoom lenses have a compensator group which moves in the same direction but at a different rate compared to the focus group.

The compensator group is also partly responsible for changing the focal length of the lens when it is zoomed.

The variator and compensator groups work together to create the change in focal length when the lens is zoomed, and the compensator group also assures that the lens remains in focus while being zoomed.

The master group serves to relay the variable magnifications from the other groups to the camera's focal plane.

It is also optically constructed to correct aberrations from the other optical groups.

Zoom Lens MechanicsZoom lenses feature complicated to extremely complex internal construction.

The zoom's mechanics not only must move the various optical groups with the correct rates of movement, but also must do this precisely while also maintaining optical alignment of the optical elements.

The movement of the various optical groups is accomplished via a series of nested barrels or sleeves.These sleeves feature machined cam-slots and cam-followers. In zoom lenses, some sleeves remain stationary while others rotate or move back and forth.

Exploded view of a camera

Cut section

Detailed working of a camera

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