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CTS Gel
Lighting · Equipment

CTS Gel

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color temperature flow roll take

Color correction gel that converts daylight (5600K) to tungsten (3200K) light. Available as Full CTS (+131 Mired), Half CTS (+65 Mired), and Quarter CTS (+32 Mired).

Technical Details

CTS gels are available in three standard strengths: Full CTS (Mired value +131), Half CTS (+65 Mired), and Quarter CTS (+32 Mired). Transmission for Full CTS is approximately 85%, with a light loss of 0.7 stops. The 0.1mm thick polyester films are heat-resistant up to 150°C and available in rolls of 61cm or 122cm width. Special variants like Double CTS (+162 Mired) allow for extreme corrections for LED panels with high Kelvin values.

History & Development

Lee Filters developed the first commercial CTS gel (Lee 204) for film production in 1971, after cinematographers had previously used improvised solutions with amber gels. Rosco followed in 1975 with the Cinegel series and standardized Mired values. The introduction of CTB gels (Color Temperature Blue) in 1978 completed the correction system. Modern LED panels began reducing the need for gels from 2010 onwards, but they remain standard for mixed lighting situations.

Practical Use in Film

Roger Deakins used Half CTS on the windows in the apartment scenes in "Blade Runner 2049" (2017) to balance warm evening light against cool LED practicals. A typical workflow: daylight sources are filtered with CTS, while tungsten lamps remain unfiltered – creating uniform 3200K lighting. In "Mad Max: Fury Road," John Seale combined Full CTS with 20K Tungsten Fresnels for a consistent desert atmosphere despite fluctuating daylight conditions.

Comparison & Alternatives

CTB gels (Color Temperature Blue) work in reverse, raising artificial light to daylight levels. Modern bi-color LED panels are increasingly replacing filtered artificial light, as they can be continuously adjusted between 2700K-6500K. ND/CTS combination gels reduce light intensity and color temperature simultaneously. For extreme corrections, dedicated Tungsten LEDs provide better color rendition than heavily filtered daylight LEDs. CTS remains indispensable for window corrections and practicals with fixed color temperatures.

From the crafts

Perspectives

Cinematographer

Ich verwende Full CTS primär für Fenster-Korrekturen in Innenräumen, wenn ich mit 3200K-Setup arbeite – das eliminiert den Blaustich und gibt mir homogene Farbtemperatur. Bei Half CTS an LED-Panels achte ich auf die Farbwiedergabe, da starke Filter den CRI-Wert reduzieren können. Der 0,7-Blendenstufen-Verlust bei Full CTS plane ich grundsätzlich in meine Lichtberechnung ein.

Director

CTS-Folie nutze ich bewusst für emotionale Farbdramaturgie – warmes, gefiltertes Fensterlicht schafft Intimität und Geborgenheit in Familienszenen. Die orange Tönung verstärkt Golden-Hour-Stimmungen auch bei neutralem Tageslicht, ohne auf die perfekte Tageszeit angewiesen zu sein. In Thriller-Szenen verwende ich bewusst ungefilterte Mischlicht-Situationen für visuellen Konflikt zwischen warmen und kalten Lichtquellen.

Producer

CTS-Folien kosten 8-12 Euro pro Quadratmeter und sind deutlich günstiger als zusätzliche bi-color LED-Miete für große Fensterflächen. Bei Außendrehs spare ich Wartezeiten auf perfekte Lichtstimmung, da ich Tageslichtvariationen mit CTS ausgleichen kann. Die Haltbarkeit von 3-5 Drehtagen bei intensiver Hitzeeinwirkung kalkuliere ich bei der Materialbestellung ein – kaputte Filter verzögern den Dreh unnötig.

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