Rosco Roscolux 1/8 CT Blue Lighting Gel - 20x24"

The Rosco Roscolux 1/8 CT Blue is a color correction filter designed to introduce a measured, precise cooling shift to tungsten and other warm light sources. In color temperature terms, a 1/8 CT Blue correction sits at the fine-adjustment end of the CTB (Color Temperature Blue) scale — it nudges a source approximately 200K cooler rather than executing the dramatic 2000K shift of a full CTB. This makes it the correct tool for mixed-source color matching scenarios: when one tungsten unit is running visibly warmer than the rest of the package, or when a daylight-balanced camera requires the tungsten sources to move just slightly toward a more neutral rendition without the output sacrifice of a denser correction filter. The high transmission characteristic of the 1/8 density means the footcandle reduction on the corrected fixture is minimal — you refine the color temperature without meaningfully changing the exposure math.

The 20×24-inch sheet format is the production-standard Roscolux cut size — large enough to cover most standard gel frames without cutting, and practical for dividing into multiple smaller pieces for a session requiring consistent correction across several fixtures. Roscolux's material formulation is heat-rated for proximity to tungsten Fresnels, PARs, and HMI sources — it maintains dimensional stability and color consistency through long sessions where cheaper gels warp and shift. In practice, a well-stored Roscolux sheet delivers the same correction at the end of a production day as it did at the first setup, which is the fundamental requirement for a color correction tool in a controlled lighting environment. For gaffers, cinematographers, and stage designers who specify color correction precisely, the Rosco dye standard is the reference point that other gel manufacturers benchmark against.