ARRI's logarithmic encoding curve (Log C, third generation) for ALEV3 sensors in the ALEXA family, combined with ALEXA Wide Gamut color space.
Log C3 (also written as LogC3) is ARRI's logarithmic encoding curve for cameras with the ALEV3 sensor. It is not a lighting or grip device, but rather camera/post-production color science: a transfer curve that translates the light captured by the camera into a flat-looking, desaturated signal that accommodates a large dynamic range within a 10-bit file.
The "Log" refers to the logarithmic relationship between exposure (measured in stops) and the encoded signal: each additional stop of exposure increases the signal by the same amount. The "C" refers to Cineon, the historical logarithmic film scan encoding, whose grayscale characteristic resembles a negative scan. The "3" denotes the third generation of the Log-C curve, introduced with the ALEV3 sensor. Log C3 is always used in conjunction with the ALEXA Wide Gamut (AWG) color space.
Material in Log C3 appears flat and desaturated when unprocessed; black and white values deliberately do not reach maximum values to preserve headroom for color correction (grading).
Log C3 is the encoding for the ALEXA generation with the ALEV3 sensor. This includes, among others, ALEXA Classic, ALEXA XT/SXT, ALEXA Mini, ALEXA LF, ALEXA Mini LF, and the AMIRA. Log C3 is recorded in ARRIRAW and in ProRes.
| Feature | Log C3 | Log C4 (Successor) |
|---|---|---|
| Sensor Generation | ALEV3 | ALEV4 (ALEXA 35) |
| Color Space | ALEXA Wide Gamut (AWG) | ARRI Wide Gamut 4 (AWG4) |
| Middle Gray | approx. 39% | approx. 32% |
| EI Dependency | EI-dependent | EI-independent |
| Dynamic Range | approx. 14–15 stops | up to 17 stops |
Since Log C3 records the image flat and desaturated, a monitoring LUT (e.g., to Rec. 709 or via ARRI Look Files) is typically applied to the image on set so that the director, camera department, and DIT see a predictable representation while the full tonal range is preserved in the recording. In color correction, grading Log C3 feels familiar to colorists because its behavior is close to that of a scanned film negative. Important in the workflow: Because the Log C3 curve is EI-dependent, the Exposure Index must be known for correct linearization or conversion – a point that its successor, Log C4, simplifies through EI independence.
Ich nutze Log-C3 hauptsächlich bei schwierigen Lichtverhältnissen, wo ich sowohl Details in den Schatten als auch in den Lichtern brauche – etwa bei Gegenlichtaufnahmen oder in Locations mit extremen Kontrasten. Das flache Monitoring-Bild erfordert allerdings präzise LUTs am Set, damit Regie und Kunden die finale Bildwirkung beurteilen können. Die nachträgliche Belichtungskorrektur von 2-3 Blenden rettet regelmäßig Takes, die in Standard-Gamma unbrauchbar wären.
Log-C3 gibt mir die Sicherheit, dass auch spontane Lichtwechsel oder unvorhergesehene Situationen bildtechnisch funktionieren – besonders bei Naturlicht-Drehs oder documentarischen Ansätzen. Die Flexibilität ermöglicht es, in der Post verschiedene Stimmungen zu testen, ohne dass das ursprüngliche Material limitiert. Allerdings muss ich mich darauf verlassen, dass das flache Set-Bild später die gewünschte emotionale Wirkung entfaltet.
Log-C3 verlängert zwar die Postproduktion um 10-15% durch zusätzliche Color-Pipeline-Schritte, verhindert aber kostspielige Reshoots durch "verbrannte" Lichter oder "absaufende" Schatten. Die Investition in Log-C3-fähige Monitoring-Hardware am Set amortisiert sich durch weniger Nachdrehs. Für Low-Budget-Produktionen mit knapper Post-Zeit ist jedoch Standard-Rec.709-Aufzeichnung wirtschaftlicher.
1. Was beschreibt „Log-C3" am besten?
2. Zu welchem Department gehört „Log-C3"?
3. Wie viele verschiedene Fachperspektiven bietet dieser Eintrag?
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