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Instead of a layer of grains making up the picture, the digital equivalent is a matrix of pixels. These work in a similar way to the grains in that when looking at a digital print, the eye merges the individual pixel rectangles into a continuous tone.
The pixels are set as a result of a sensor taking the light from the subject and processing it through a grid of Charge Couple Devices. (CCD). Each CCD is designed to measure the amount of light that hits it. The CCD only records in levels of black and white, and so is only able to record the brightness of a scene.
The way that colour is recorded is derived from a discovery made in the mid 1920’s, when it was discovered that you could get colour photographs from black and white film by using a set of coloured filters. If the same scene was shot three times on black and film using red, green and blue filters, and then projected together through the same filters, the result was a colour picture of the scene.
This basic idea is used today in the digital camera. The CCD’s are arranged into a grid pattern where each cell of the grid is filtered to only capture the level of red, green or blue wavelengths. The result is a set of three greyscale images that can be tinted and re-combined to produce the required coloured image.
The great advantage that digital photography offers over the traditional film is that the camera picture is digital and so can be easily manipulated by a computer. In fact, most digital cameras are now supplied complete with editing software to manipulate the finished picture. In some cameras it is even possible to capture the original greyscale images before they are combined. This RAW format allows the manipulation of the original picture elements providing almost unlimited scope for creativity.
This article has been written for www.TopDigicam.com by Roger Titley and all copyrights are reserved. It may only be reproduced if this copyright notice and the site link are included.
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