Color correction
Color correction is a process used in stage lighting, photography, television, cinematography, and other disciplines, which uses color gels, or filters, to alter the overall color of the light. Typically the light color is measured on a scale known as color temperature, as well as along a green–magenta axis orthogonal to the color temperature axis.
This article is about color correction using lighting and camera filters. For video color correction in post-production, see Color grading. For color correction of still images in post-production, see Color balance. For mutual color correction of digital images, see Color mapping.
Without color-correction gels, a scene may have a mix of various colors. Applying color-correction gels in front of light sources can alter the color of the various light sources to match. Mixed lighting can produce an undesirable aesthetic when displayed on a television or in a theatre.
Conversely, gels may also be used to make a scene appear more natural by simulating the mix of color temperatures that occur naturally. This application is useful, especially where motivated lighting (lending the impression that it is diegetic) is the goal. Color gels may also be used to tint lights for artistic effect.
Gel nomenclature[edit]
The main color-correction gels are "color temperature blue" (CTB) and "color temperature orange" (CTO). A CTB gel converts tungsten light to "daylight" color. A CTO gel performs the reverse.[3] Note that different manufacturers' gels yield slightly different colors. As well, there is no precise definition of the color of daylight since it varies depending on the location (latitude, dust, pollution) and the time of day.
Gels that remove the green cast of fluorescent lights are called "minus green". Gels that add a green cast are called "plus green".[3] Fractions such as 3/4, 1/2, 1/4, and 1/8 indicate the strength of a gel. A 1/2 CTO gel is half the strength of a (full) CTO gel.
Color correction in software[edit]
Software applications such as Adobe Photoshop allow the user to correct colors to achieve the desired results in an image. Multiple tools available to correct colors, match colors, or change colors of images or of parts of images.
