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By: Jo Chew
Date: 4/11/2006

The term "camera" comes from the Latin "camara obscura", which means "dark room".

This type of room was an artist's tool in the middle ages. A light proof room, in the form of a box, with a convex lens at one end, and a screen that reflected the image at the other was used by the artists to trace images and later produce paintings.

In the 19th century, "camera" referred to a device for recording images on film or some other light-sensitive material. It consisted of a light-proof box, a lens through which light entered and was focused, a shutter that controlled the duration of the lens opening and an iris that controlled the amount of light which passed through the glass.

Joseph Nicephore Niepce producted the first negative film image in 1826. This is considrered as the birth of photography. Initially, such photographic cameras didn't differ much from the "camara obscura" concept. They were in the form of a black box, with a lens at the front and a film plate at the back. The initial image setup and focusing was done on an upside-down projection, which a photographer could only see when covered with a black sheet.

The first commercial photographic cameras had a mechanism for manual transport of the film between exposures, and a viewfinder, or eyepiece, that showed the approximate view as seen by the lens.

Today, we use the term "camera", in film, photography, television and multi-media.

They project the image onto different "targets", but they all use light and lenses.

To understand CCTV you don't need to be an expert in cameras and optics, but it helps if you understand the basics

Many things are very similar to what we have in photography, and since every one of us has been, or is, a family photographer, it will not be very hard to make a correlation between CCTV and photography or home video.

In photographic and film cameras, we convert the optical information(images) into a chemical emulsion imprint(film). In television cameras, we convert the optical information into electrical signals.

They all use lenses with certain focal lengths and certain angles of view, which are different for different formats.

Lenses have a limited resolution and certain distortions(or aberrations), but this is more obvious in the film cameras. This is because the film resolution is still far better than the electronic camera resolution(as till 1995).

For illustration purposes, high resolution CCD chips these days have something like 752x582 pixels(picture elements), whilst 100 ISO 35mm colour negative film has a resolution of approximately 4000x3000 elements(film grains).

In the last year or two, another type of camera has emerged onto the market. This is a camera used with computers for both video conferencing and digital image storage. A camera like this, uses a CCD chip as an imaging device, but instead of producting an electronic signal or storing the image on film, it converts the image to digital format and stores it on a micro disk in the camera or outputs it in digital format, so as to be transferred to a computer. This is only a still camera, but the day when a "motion" digital camera appears on the market has now arrived.