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What is a Camera ?

What is a camera?

Essentially, a camera is a device consisting of a light-tight box which has an opening covered by a lens in one wall. This lens forms a real image image of the object upon a film of light sensitive material placed on the opposite side. The film is chemically processed to make a negative.

• A pinhole camera, instead of a lens, has a hole of 0.016 inch in diameter which produces the image. But the image is blurred. Being a very small hole, the quantity of light passing through is very little and need very long time to expose the film.

• In a box camera, either the shutter speed is fixed with variable aperture or with a fixed aperture and variable shutter speed.

• Bellows type camera are usually used for large size films .

• Small format (35mm and below) are often of the tube type. They are earlier versions to SLR type. High-class models are quipped with coupled rangefinders (for focusing) interchangeable lenses and shutter speeds up to 1/1250^th of a second.

• The medium format ‘Twin-lens Reflex’ camera has two compartments, one above the other. The lens of the two parts have exactly the same focal length. A mirror positioned at 45º inclinations reflects the image to the viewfinder above in the top compartment while the lower one takes the picture. Both lenses move simultaneously.

The viewing image remains visible all the time, but the viewpoint difference (parallax) of the two lenses means that the framing on the top screen is not exactly identical with that on the film. Hence, this poses a problem while capturing faces or portraits – the head portion is eliminated and the neck is very prominent.

PARTS OF AN SINGLE LENS REFLEX (SLR) CAMERA

1. Shutter speed dial/film speed set ring
2. Shutter release button
3. Film advance lever
4. Frame counter
5. Strap hook
6. Hand grip
7. Self –timer lever
8. Lens release button
9. Hot shoe
10. Film rewind crank
11. Film rewind knob and film compartment opening knob
12. Film speed setting window
13. Aperture setting ring
14. Focusing distance scale marked in meter and feet
15. Focusing ring
16. Depth-of-field scale
17. Depth-of-filed preview lever
18. ME (Multi exposure) lever
19. Exposure measurement button (correct/over/under)
20. View finder eye-piece
21. Rewind shaft
22. Film loading chamber
23. Battery compartment cover
24. Tripod fixing socket
25. Film Guide rails
26. Sprocket
27. Back cover
28. Film pressure plate
29. Film rewind button
30. Film take-up spool
31. Flash synchro contact
32. Data back contact
33. Window to view film data

* Image from uni. victoria website

SINGLE LENS REFLEX CAMERA (SLR)

Most of the modern 35 mm (small format) and medium format cameras are all of this type. A mirror in the camera body is pivoted at an angle of 45 degrees just in front of the focal plain shutter. The light rays passing through them is reflected above the focusing screen. The focused image on this screen is seen again through a prism placed at the top.

The prism is called ‘penta prism’ since it has five sides and it turns the light rays to 90 degrees with the view finder without reversing the image. The light rays take a total internal reflection inside the prism.

The stop value (f) or the aperture is set before the exposure is made. When the shutter is released the deviating mirror is automatically swung up above and the focal plane shutter is mounted directly in front of the film, momentarily exposes the film.

The advantage of an SLR camera is that the photographer is able to see the image exactly what the lens is viewing, (the field of coverage).

But the disadvantage is that (it is not once you get used to it) there is a black out in the view finder at the exact moment of exposure.

The set aperture closes to the set value only just before the exposure is made. Otherwise it is fully opened to allow maximum light through the lens for convenient sharp focusing.

WORKING OF AN SLR CAMERA

Most of the modern 35mm (small format) and medium format are all of this type. A mirror in the camera body is pivoted at an angle of 45⁰ just in front of the focal plane shutter. The light rays passing through it are reflected above to the focusing screen. The focused image on this screen is seen again through a prism placed at the top. The prism is called ‘Penta Prism’ since it has 5 sides and it turns the light rays to 90⁰ to the viewfinder without reversing the image. The light rays take a total internal reflection inside the prism.

The stop value (f) or aperture is set before the exposure is made. When the shutter is released the deviating mirror is automatically swung up above and the focal plane shutter mounted directly in front of the film, momentarily exposes the film

*** Diagrams visible at www.howstuffworks.com

HANDLING THE CAMERA

• While focusing, see that your finger is not blocking the lens.
• When taking a picture from top angle, sometimes your camera case or the sling will get into the field of view.
• In standing posture, more stability is achieved by butting the fore- arm firmly against chest.
• Always use the camera sling. Put it around your neck to protect your camera from falling.
• Use lens hood to protect your lens. It also blocks stray light entering the lens.