The Importance of Bit Depth
Each digital file you create (capture or scan) is capable of representing a specific number of colors. This capability, usually referred to as the ‘mode’ or ‘color depth’ of the picture, is expressed in terms of the number of ‘bits’. Most photos these days are created in 24-bit mode. This means that each of the three color channels (Red, Green and Blue) is capable of displaying 256 levels of color (or 8 bits per channel). When the three channels are combined, a 24-bit image can contain a staggering 16.7 million separate tones/hues.
The Digital Photograph
Computers are amazing machines. Their strength is in being able to perform millions of mathematical calculations per second. To apply this ability to working with images, we must start with a description of pictures that the computer can understand.
This means that the images must be in a digital form. This is quite different from the way our eye, or any film-based camera, sees the world. With film, for example, we record pictures as a series of ‘continuous tones’ that blend seamlessly with each other. To make a version of the image that the computer can use, these tones need to be converted to a digital form.
The process involves sampling the image at regular intervals and assigning a specific color and brightness to each sample. In this way, a grid of colors and tones is created which, when viewed from a distance, will appear like the original image or scene. Each individual grid section is called a picture element, or pixel.