Brief description of the working of modern day digital cameras, their parts and cut section revealing the mechanism of telescopic lens.

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

3.  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.

4.  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.

5. 1. Lens Alignment
2. Flash Pop Up Button
3. Lens Release
4. Depth of Field preview
5. Lens contacts
6. Mirror
7. Grip
8. Shutter Release Button
9. Focus Assist Beam
10. Pop Up Flash

6. 1. Viewfinder
2. DiopterAdjustment
3. Rubber Eye-cup
4. Joystick Dial
5. Exposure Lock/Zoom Button
6. Focus Point Selector/Zoom Button
7. Write Indication Light
8. Jog Dial and Set button
9. On/Off Button
10. Erase Button
11,12,13,14- UI buttons
12-LCD screen

7. 1. Light for LCD Display
2. Auto focus/white balance
3. Drive/ISO
4. Shutter Button
5. Top Dial
6. Metering/Flash Compensation
7. LCD Screen
8. Hotshoe
9. Exposure control Dial
10. Flash

8.  Aperture 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.

9.  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.

11.  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 100 mm to 400 mm 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 with prime lenses.
 It features very complicated internal construction.

12. A simple zoom lens system

13.  The three lenses of the afocal system areL1, L2, L3.
 Lens L3 is fixed, but lenses L1 and L2 can be moved
axially in a particular non-linear relationship, changing
the overall focal length of the system.
 While the negative lens L2 moves from the front to the
back of the lens, the lens L1 moves 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.

14.  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 lens 50 mm lens
70 mm lens 210 mm lens

15. 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.

16.  The 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, and
the master group.

17.  The focus group moves forward or backward as necessary for
focusing the lens.
 The variator group of 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 group of 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.

18.  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.

19.  Zoom 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.

20.  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.