Merging created not through physical mixing of colours but by using the theory of perception of colour is called as optical mixing. In painting, optical mixing is done to make the painting appear brighter. Mixing of two colours physically may result in losing of intensity. But optical mixing retains the intensity of colours because it only appears to create a brighter colour. Optical mixing technique is commonly used for creating a glazing effect in painting and is popularly used in Impressionist and pointillist painting. Colour photos in newspaper is an example of optical mixing which appears to make pictures or images with small dots rather than a solid colour. Optical mixing makes the eye of the viewer to mix bits of original colour placed near to each other. Optical illusion in picture makes the picture more luminous when viewed from a distance.