4.2.3 Lens system
The function of the lens system is to project an image onto the CCD light sensor. A well-designed system ensures that the image is sharp – in focus – and bright. To achieve this, what is needed is a good-quality glass lens (or rather a series of lenses) and accurate focusing. The brightness of the image depends upon the size of the lens. The bigger the lens, the brighter the image, but bigger lenses are more difficult to make and therefore more expensive. Also, of course, bigger lenses mean bigger and heavier cameras. As so often in technology there are trade-offs between several factors. In this case, brightness of the image (and therefore the ability of the camera to operate in low light levels) interacts with cost, size, weight and image quality. I shall discuss focusing in more detail later, after describing the light sensor.