Color casts (or a color cast) are tints of a particular color, usually (but not always) unwanted and affects the whole, or portion, of a photographic image evenly.
There are types of light that can cause film and digital cameras to have a color cast. Illuminating a subject with light sources of different color temperatures will usually cause color cast problems in the shadows. In general, the human eye does not notice the unnatural color, because our eyes and brains adjust and compensate for different types of light in ways that cameras cannot.
WHEN COLOR CASTS ARE UNWANTED! When certain footage shows a color cast that is unwanted, it can often be removed. These type of color casts can be fixed in post production by a Di Colorist. The below image is a good example of removing a color cast in the post production color correction process . While the left image would be a great look for a story in a disco, bar or an other party type of scene, the right image has been neutralized by the di colorist with a proper black and white point and the color cast has been removed.
One of the Hollywood industry programs for color correction is Davinci Resolve. The type of color correction will depend on what the director needs and what kind of story he wants to tell. For instance, the left image, the original (even though it needs some work), can be used to tell the story of a disco or party with these colored lights, but if for some reason the director wants a clean image it can be achieved by a Di Colorist in special color correction programs such as Davinci Resolve.
WHEN ARE COLOR CASTS WANTED? Colors tell stories and so do color casts, with colored lights and/or colored gels, DOPs (director of photography) create great scenes to tell stories of bars, parties, streetlights etc.
An actor could for instance be standing next to a neon light and that light color reflects or shines on the actors face. Or at night standing next to a street with passing cars where some cars have yellowish and other blueish lights, these color casts can also be motion automated and recreated by the director of photography to have color cast changing color and even moving (simulating cars passing by). Illuminating a subject with light sources of different color temperatures will usually cause color cast problems in the shadows, a true director of photography will have mastered the art of correctly and deliberately adding color casts to the scene to support certain strong story telling.
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