The human mind is full of visual images. The difference between an artist or a designer and a common man actually lies in the mental skill of an artist or a designer to utilise this raw material for the process of creating something "new". It is also interesting to understand the actual process of visual perception in the brain. Light enters the eye through the external lens of cornea and then passes through the pupil. A light-sensitive retina acts like a film of the camera. The retina is a cluster of 130 million microscopic receptors containing light-sensitive chemicals called photo pigments. There are two basic types of cells -- cones that are used for daytime vision and rods that are used for seeing at night-time.

The basic mechanism of your eye works like the camera. The colour for instance has no meaning outside your brain, except as a variation in wavelengths of light and is reflected by different materials. Because different cones on your retina have photo pigments that respond best to the particular wavelengths of light, the visual system is able to record information of wavelengths. The brain interprets this to create a sensation that we perceive as colour.

If you think of the sharpness of the rods and the cones on the retina and the fineness of the retina grain and the diameter of the cones, which is about 115 millionth of 1 metre, the sharpness of the vision means that the eye can see a 0.02mm thin line less than the width of human hair viewed from 30 cm away.

The eye is able to respond to a remarkable range of light intensity, the maximum being a million times more than the minimum intensity that it can detect. The minimum detectable intensity is so low that one could see a candle burning 8 km away!