Light Art: What is a Camera ?

Wednesday, December 26, 2007

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.