Last Updated 3 months ago
Definition
CTO (Color Temperature Orange) is an orange-colored color-correction gel used to warm a light source by shifting its color temperature downward. The most common application is converting daylight-balanced lights (around 5600K) to match tungsten (around 3200K). CTO is one of the most frequently used gels on film sets and is a standard tool for both the lighting and grip departments.
Where CTB cools the light, CTO warms it—making it essential for controlling mood, matching sources, and keeping skin tones consistent.
What CTO Does
Different light sources emit different color temperatures. Without correction, scenes shot with mixed lighting can look mismatched or unnatural. CTO allows filmmakers to bring those sources into alignment.
CTO accomplishes:
- Daylight ? Tungsten conversion
- Warming overly cool sources
- Matching LEDs or HMIs to practical lamps
- Creating warm stylistic lighting
- Correcting mixed lighting environments
It ensures a cohesive look, clean white balance, and natural skin tones.
Common Strengths of CTO
CTO gels come in multiple densities, each offering a different degree of warming:
- Full CTO ? Converts 5600K to ~3200K (daylight ? tungsten)
- ½ CTO ? Produces a warm daylight balance; useful at golden hour
- ¼ CTO ? Mild warm tint; great for talent key lights
- ? CTO ? Very subtle warmth; often used to enhance complexions
DPs and gaffers select the strength based on the desired look and how the camera is balanced.
When CTO Is Used
1. Balancing Daylight to Tungsten
When shooting in a tungsten-balanced interior, daylight coming from windows or daylight LEDs must be warmed with CTO.
2. Matching LEDs and HMIs to Practical Lamps
Household bulbs are warm. CTO helps match professional lights to those practicals so the scene feels cohesive.
3. Cosmetic Enhancement
CTO is commonly used on faces—¼ or ? CTO adds subtle warmth, improves skin tones, and prevents talent from looking overly cool under daylight setups.
4. Creating Mood or Stylized Warmth
Directors may push scenes warmer for emotional or narrative reasons. A strong CTO on key or fill can support that look.
CTO vs. CTB
- CTO (Color Temperature Orange): Cools ? Warm (Daylight ? Tungsten)
- CTB (Color Temperature Blue): Warm ? Cool (Tungsten ? Daylight)
These two gels are the foundational color-correction tools in lighting.
Practical Considerations
- Full CTO reduces light output (all gels cut some intensity).
- Tungsten units require spacing from the gel to avoid burning or warping.
- Even with modern RGBWW LEDs, CTO gels remain useful for precise spectral correction or matching on mixed sets.
Related Terms
- CTB – Converts tungsten to daylight by cooling the light.
- Colour Temperature – Measurement of a light source’s warmth or coolness.
- Diffusion – Softens light; often used alongside CTO.