Thin plastic sheets of polycarbonate or polyester mounted in front of lights to alter color or diffuse the beam.
Technical Details
Modern color gels are made of polycarbonate or polyester and can withstand temperatures up to 200°C. Light transmission varies between 15% and 90% depending on the color, while the absorption rate can reach up to 85% for darker gels. Lee Filters produces over 300 different color variations, and Rosco offers 400+ options. CTB (Color Temperature Blue) filters correct 3200K tungsten light to 5600K daylight, and CTO (Color Temperature Orange) filters do the reverse. Diffusion gels reduce light intensity by 0.25 to 2 stops while simultaneously scattering the light.
History & Development
In 1884, Louis Hartmann developed the first gelatin color filters for theatrical lighting. Eastman Kodak introduced standardized Wratten filters for cinematography in 1930. Rosco revolutionized the market in 1952 with heat-resistant plastic gels. Lee Filters established the industry-standard numbering system in 1967. While the digital revolution from 2000 onwards reduced the need for correction filters, it increased their creative use for look development.
Practical Use in Film
Cinematographer Roger Deakins used orange CTO gels in "Blade Runner 2049" for the dystopian exterior scenes. "Mad Max: Fury Road" employed Amber filters (#204) for the desert sequences. In night shoots, 1/4 CTB filters (#201) are regularly used to match LED panels to moonlight. The gels are mounted in front of lights using clips or magnetic frames, ensuring sufficient distance from the light source. Advantage: cost-effective, immediate color change. Disadvantage: light loss and limited durability with strong heat development.
Comparison & Alternatives
While color gels are attached to lights afterward, modern LED panels offer built-in color mixing without light loss. ARRI SkyPanels or Litepanels Geminis allow for stepless color temperature adjustment from 2800K to 10000K. Dichroic filters in HMI lights produce purer colors but cost ten times as much. Color gels remain standard for budget productions and for special effect colors not covered by LED systems. For continuous operation, glass filters are better suited, while gels are preferred for one-off setups and frequent color changes.