Color Temperature Orange

Overview

Color Temperature Orange (CTO) refers to a series of orange conversion gels that are stretched or clipped in front of light sources on set to lower their color temperature. A classic application is converting daylight-balanced light (around 5500–5600 K) to artificial light/tungsten levels (around 3200 K), so that daylight sources like HMI and LED fixtures can match existing incandescent light or practical household fixtures. CTO is the warm counterpart to CTB (Color Temperature Blue), which conversely raises artificial light to daylight.

CTO is available in several density levels (Full, 3/4, 1/2, 1/4, 1/8), allowing the warming effect to be metered – from full conversion to a subtle warm touch. The main manufacturers are Rosco (product line RoscoSun) and LEE Filters (CT Orange series).

Technical Data

The conversion values are considered guidelines for a 5500 K daylight source and vary slightly depending on the manufacturer (different Mired shift). Rosco Full CTO has a Mired shift of approximately +167, LEE Full CTO approximately +159.

The gels are made of heat-resistant, deeply dyed polymer/polyester and are available as sheets as well as rolls. Each conversion level incurs a certain light loss (full conversion absorbs noticeably more light than the weaker levels).

On-Set Usage

• Matching daylight sources (HMI, LED) to existing artificial light or practical household fixtures in the frame.
• Warming the overall lighting mood for interiors, evening, or golden hour looks.
• Using weak levels (1/4, 1/8 CTO) on fill or key lights to make skin tones appear warmer and more flattering.
• With modern, color temperature-variable LED lights, it is often replaceable via the menu, but on physical fixtures (tungsten, HMI), CTO remains a standard tool.

The gel is attached using gel frames, on barndoors with clothespins (C47), or in filter frames in front of the fixture. It is important not to let the gel lie directly on hot glass to avoid burning.