Gel; Diffusion Gel; Filter Gel; Color Gel; Lighting Gel;
Gels are transparent coloured material used to modify lights for photography, video and theater. Light is projected through the gel to create coloured effects in the scene being photographed. Some gels modify the light for colour correction. These have specific colour to compensate for particular light conditions.
Gels which modify light in specific ways may also be considered to be photographic filters if placed in front of a lens where they will affect the character or colour of incoming light.
Modern gels are made from a variety of different materials. Gels are mounted in a frame which is slipped into the front of a light fixture in the light beam. In photography, when used as a filter, they are stiffer and normally mounted in some sort of frame in front of the lens.
Gels have a limited life. The light shining through them fades the colours. Gels with more saturated colours fade faster.
In digital photography there is less need for corrective colour gels. The effects can be compensated in-camera by the use of white balance settings. However, gels may be needed to reproduce scenes or specific light conditions for special creative purposes. This is especially true where mixed lighting conditions would be misinterpreted by white balance metering. Non-corrective colours may also be used to create mood, atmosphere or dramatic conditions in the scene. In this case combinations of various gels may be used to create customized light conditions.
All gels used for colour correction are matched to colour temperature charts. Some gels are calibrated with specific colour temperatures for correcting light of particular types. Some manufacturers have specific schemes of calibration for their filter gels. Refer to specific manufactures for details.
Some gel types have generally recognised names. For example these common gel types have specific colour results…
CTB (color temperature blue) – converts tungsten light to ‘daylight’ color.
CTO (color temperature orange) – converts daylight to tungsten
Gel strength is indicated by fractions such as 3/4, 1/2, 1/4, and 1/8. 1/2 CTB gel is half the strength of a full strength CTB gel.
Note: ‘Daylight’ is not a specific term. Gels tend to be based on standards set by individual manufacturers. It is therefore a consumer decision on what to buy to for specific colour corrections.
Fluorescent lights emit a greenish colour cast. Gels that remove it are called ‘minus green’. Gels adding a green cast are ‘plus green’.
Diffusion and other filter types
A number of non-color gels exist to create special light effects. Gels exist to create diffusion effects on the light. Other effects include opal, skylight, star-effect and various softening filters and light effect filters. Most manufacturers have a range of these special effect gels. Refer to individual manufacturers websites for full details.