Colour centre in humans as an area specialized for colour vision. V2, also called the prestriate cortex, is believed to have a small role in colour processing by projecting signals from V1 to the V4-complex. Whether or not colour selective cells are present in V2 is still being investigated. Some optical imaging studies have found small clusters of red-green colour selective cells in V1 and V2, but not any blue-yellow colour selective cells. Other studies have shown that V2 is activated by colour stimuli, but not colour after images.[8] V4 also has feedback on V2, suggesting that there is a defined network
Colour cast Improper timing or imbalanced chemical mixtures can cause unwanted casts. Colour casts can also occur in old photographs due to fading of dyes, particularly under the action of ultra violet light. These may be correctable on a scanned version of the photograph with image editing techniques. Most digital cameras try to automatically detect and compensate colour cast and usually have a selection of manually set white balance settings to choose from. Otherwise, photo editing programs, such as Photoshop, often have built in colour correction facilities. For film, blue filters and amber filters are used to counter casts. Amber filters are