Rosco 91

Overview

"Rosco 91" does not refer to a spotlight, a grip device, or an ANSI lamp code, but to a color filter (gel) from the manufacturer Rosco. The number 91 stands for the color "Primary Green" and is available in both the standard Roscolux series and the more heat-resistant Supergel series under the same number (often referenced as R91).

It is a strong, saturated green. As the name "Primary Green" suggests, the filter is designed as the primary green color for additive color mixing: together with a primary red and a primary blue, almost any color can be mixed using three separately controlled light sources. Such filters are used in the beam of spotlights (in color frames, filter drawers, or gel clips) to color the white source light.

Technical Data

Verified key data according to manufacturer and dealer information:

The high degree of saturation means a correspondingly strong light loss: with only about 7% transmission, the filter absorbs about 3.8 stops, as it absorbs almost everything outside the green spectrum. Sheet material is also available from dealers in larger rolls; dimensions can vary depending on the batch and distributor.

Usage on Set

• Rich Green: for strongly colored light, e.g., theater and show lighting, stage washes, and stylized effect moods.
• Additive Three-Color Systems: as the green component alongside primary red and primary blue, to create mixed colors using three separate lighting circuits.
• Effect and Background Lighting: for colored backgrounds, cyc lighting, or green accents in film, TV, and studio.

When using, the high light loss must be factored in (requiring correspondingly more powerful or closer positioned spotlights), as well as heat generation: saturated gels get hotter in the beam path and age faster with strong quartz/halogen sources. For high thermal loads, the Supergel variant is preferred. With LED sources, gel filters are increasingly being replaced by onboard color mixing, but in classic conventional operation, R91 remains a standard green.