If you stare at a strong colour and then look at a white background, you will see an afterimage. There are negative and positive afterimages. Negative afterimages are more common and longer lasting. They have the complimentary hue and opposite brightness of the original stimulus. For example, if you stare at a red circle and then look at a white wall, you will see a green afterimage. Positive afterimages are a result of an extension of receptor and neural processing after the stimulation. Positive afterimages tend to be rare and short in length. An example of a positive afterimage is when you would continue to see the light of a flashbulb after someone takes your picture. Our perception of the size of the afterimage depends on its distance from us. The farther away the afterimage, the larger it appears.