Cinematographer
Aus DoP-Perspektive ist dieses Element essentiell für die visuelle Gestaltung. Es ermöglicht mir die gewünschte Farbstimmung und das ästhetische Bild konsistent umzusetzen.
Color Temperature Blue (CTB) gel that corrects tungsten light (3200 K) to daylight balance (approx. 5600 K).
Overview
"Daylight Correction" in film lighting refers to raising the color temperature of a tungsten light source (artificial light, 3200 K) to daylight level (around 5600 K). This is achieved with blue correction gels, known as CTB (Color Temperature Blue). The gel is placed in front of the light source or taped to windows as a roll to match a tungsten lamp to incoming daylight or to keep mixed lighting color-consistent.
The opposite conversion – converting daylight (e.g., HMI) down to artificial light – is done with orange CTO (Color Temperature Orange) gels. CTB and CTO are thus complementary tools for set color correction.
How it Works
The correction strength is specified in Mired shift: CTB creates a negative Mired shift, thus cooling the light. Since the blue gel absorbs a significant portion of the warm spectrum, full correction results in a considerable loss of light output – a key practical factor in planning lighting levels.
The gels are available in graduated densities (Full, 3/4, 1/2, 1/4, 1/8 CTB). Weaker densities are used for partial correction or effects like cool shadow or moonlight; full density covers the coldest midday sun.
Technical Data (Example LEE 201 / 202)
| Gel | Conversion | Transmission | Mired Shift |
|---|---|---|---|
| LEE 201 Full C.T. Blue | 3200 K → 5700 K | approx. 34% | −137 |
| LEE 202 Half C.T. Blue | 3200 K → 4300 K | approx. 55% | −78 |
The low transmission of the Full CTB gel illustrates the high light loss of full correction. Rosco offers comparable products in its Cinegel line (e.g., Full Blue).
Set Usage
- Matching tungsten lights (Fresnels, open-face, incandescent practicals) to daylight through a window.
- Taping CTB rolls to window panes to trim interior light to daylight (often combined with ND).
- Standardizing mixed lighting situations so a single white balance works for the entire scene.
- Partial corrections (1/2, 1/4 CTB) for intentionally cool, but not fully neutralized, moods.
From the crafts
Perspectives
Producer
Diese professionelle Lösung erhöht die Produktionseffizienz und reduziert Post-Production-Anforderungen. Sie ermöglicht flexible, schnelle Anpassungen während des Drehs.
Gaffer
Als Gaffer ist dies ein unverzichtbares Werkzeug meines täglichen Handwerkszeugs. Es ermöglicht mir professionelle Lichtkontrolle und schnelle Anpassungen auf Set, was Zeit spart und Qualität sichert.
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