Double CTB: Very strong blue color correction gel (approx. -12 Mired) — fully converts tungsten artificial light to cool daylight color temperature.
Definition
The Double CTB is a color correction filter that corrects artificial light by two full stops from 3200K to 5600K. The filter converts tungsten light to daylight quality.
Practical Application
This lighting element is used in various professional scenarios:
- Color Correction: Matching tungsten lamps to daylight or HMI sources
- Light Control: Reduces light output by approximately 2 f-stops
- Effect Design: Creates cool color moods with mixed light sources
- Set Efficiency: Avoids yellow cast in post-production
Technical Details
Important technical features include:
- Light Transmission: approximately 25% (2 stops loss)
- Color Temperature Shift: -2800K (from 3200K to 5600K)
- Available as gel filter, clip-on, or permanently mounted variant
- Standard sizes for luminaires from 150W to 20kW
Practical Tips
- Compensate exposure by 2 stops or raise the luminaire higher
- For LED panels, prefer direct color temperature change
- Use a light meter with color temperature display
- Protect the filter from heat - maintain a safe distance with high wattages
Professional Standards
In professional film and television production, CTB filters enable:
- Uniform color temperature with mixed light sources
- Quick adjustment without changing lamps
- Reduced color grading effort
- Broadcast-compliant color values according to Rec. 709
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