Bit Depth and its Significance

Even a student studying in an elementary school knows that there are three important colours-Red, Green, and Blue which are commonly denoted as R, G, and B. All other colours can be derived from just these three. This is the reason why R, G, and B are also called the "primary colours".

- Ashok Kandimalla

Ashok Kandimalla has been in the photographic field for over three decades and has extensive experience in both film and digital photography.

Being an electronics engineer by profession and a photographer, he possesses a unique and deep insight into the technical aspects of digital photography and equipment. He has published more than a 100 articles on photography and some of his writings have also been published in the well-known international magazine Popular Photography. An avid collector of photographic books and vintage cameras, Ashok has a keen interest in the history of photography and a passion for sharing his knowledge on photography through teaching and writing. He is the only Indian photographer to be featured on the Nikon Centenary website.

He is presently working as a Management and Engineering consutant. He can be reached at [e-mail].

While most digital cameras can record colour, the sensor in a camera is not sensitive to colour directly. To register colour, every photo site, commonly called a pixel has a coloured filter in front of it. In almost all sensors, there are two pixels with a green filter for every red, and blue pixel. Thus, the R, G, and B pixels are in the ratio of 1:2:1 (Picture 1).

This arrangement of pixels is called the Bayer Pattern, named after its inventor Dr. Bryce Bayer, a scientist from Kodak. It allows the camera (or suitable software) to generate any colour at every pixel and the process employed for synthesising colour this way is called 'Demosaicing".

Before we go further, we need to understand two terms 'gamut' and 'colour space. Any device will have a limitation on the number of colours it can handle. Think of a device, say a camera. Assume that all colours that this camera can record are contained in a box - just like a kid would have a crayon box. Let us say you have captured an image with your camera.