Colour cast
Encyclopedia
A colour cast is a tint of a particular colour, usually unwanted, which affects the whole of a photographic image evenly.
Certain types of light can cause film and digital cameras to have a colour cast. In general, the human eye does not notice the unnatural colour, because our eyes and brains adjust and compensate for different types of light in ways that cameras cannot.
In film, colour casts can also be caused by problems in development. Improper timing or imbalanced chemical mixtures can cause unwanted casts.
High end digital cameras try to automatically detect and compensate colour cast and usually have a selection of manually set White Balance settings to chose 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 used to reduce the blueish tint caused by daylight. Blue filters reduce the orange colour caused by incandescent light.
A variety of coloured filters in varying degrees of intensity are available. Kodak's amber filters, for example, vary from palest yellow ("81C") to deepest amber ("85B"). A photographer chooses which filter to used based on the quality of the ambient light. Colour temperature
meters can read the temperature
of the existing lighting conditions and guide the selection of the filter. Clouded sky, for example, requires a paler amber than clear blue sky. If a filter is unavailable, flash
is an alternative solution which usually provides enough neutral white light to counter the cast.
In the case of film, if photographs all contain the same cast, it is usually indicative of improper chemical development. If the film itself does not contain any cast, it can be reused to create another set of photographs in proper chemical conditions. If the film contains a cast, filters can be used during photo processing to correct it.
Certain types of light can cause film and digital cameras to have a colour cast. In general, the human eye does not notice the unnatural colour, because our eyes and brains adjust and compensate for different types of light in ways that cameras cannot.
In film, colour casts can also be caused by problems in development. Improper timing or imbalanced chemical mixtures can cause unwanted casts.
Solutions
A variety of coloured filters in varying degrees of intensity are available. Kodak's amber filters, for example, vary from palest yellow ("81C") to deepest amber ("85B"). A photographer chooses which filter to used based on the quality of the ambient light. Colour temperature
Color temperature
Color temperature is a characteristic of visible light that has important applications in lighting, photography, videography, publishing, manufacturing, astrophysics, and other fields. The color temperature of a light source is the temperature of an ideal black-body radiator that radiates light of...
meters can read the temperature
Color temperature
Color temperature is a characteristic of visible light that has important applications in lighting, photography, videography, publishing, manufacturing, astrophysics, and other fields. The color temperature of a light source is the temperature of an ideal black-body radiator that radiates light of...
of the existing lighting conditions and guide the selection of the filter. Clouded sky, for example, requires a paler amber than clear blue sky. If a filter is unavailable, flash
Flash (photography)
A flash is a device used in photography producing a flash of artificial light at a color temperature of about 5500 K to help illuminate a scene. A major purpose of a flash is to illuminate a dark scene. Other uses are capturing quickly moving objects or changing the quality of light...
is an alternative solution which usually provides enough neutral white light to counter the cast.
In the case of film, if photographs all contain the same cast, it is usually indicative of improper chemical development. If the film itself does not contain any cast, it can be reused to create another set of photographs in proper chemical conditions. If the film contains a cast, filters can be used during photo processing to correct it.