Scene-referred camera encoding
Why cameras record Log, why the flat image preserves dynamic range, how Log differs from RAW and gamma, why every log curve needs the correct camera gamut, and how to normalise footage without LUT magic.
Log is not a grey style and not unfinished video. It is a non-linear way to pack a large scene-exposure range into a limited digital signal without forcing highlights into hard display contrast inside the camera.
Quick reference
Gamma and gamut form a source pair.
One common Sony production pair.
Generation/version matters for interpretation.
They are different layers of the image pipeline.
The 'flat' picture is not the intended final look. Log is an encoding designed to carry scene information efficiently before an appropriate transform and grade.
A modern sensor can distinguish many stops between deep shadows and clipped highlights. If that range is immediately forced into a contrasty display-oriented encoding, much of the headroom is either clipped or receives an awkward distribution of code values. Log-like encoding compresses highlights while preserving useful precision through mid and lower exposure regions for post-production.
The idea is close to a logarithmic relationship: equal multiplicative changes in scene exposure — stops — receive more even spacing in the encoded signal than they would in a linear representation. Real camera curves are usually piecewise and do not have to be a pure mathematical logarithm across the whole range. LogC4, S-Log3 and Blackmagic Film are therefore different specifications, not one universal Log.
A Log signal is not yet intended for direct display rendering. It preserves scene relationships before the creative/display transform, so scene black does not have to sit at display black and highlights do not have to be stretched to 100% display white. If a wide camera gamut is also interpreted as Rec.709 without a transform, saturation and hue relationships are further distorted. A flat viewer image is therefore a consequence of display interpretation, not a lack of information.
Gamma/transfer describes tonal encoding but not chromaticities. ARRI LogC4 therefore normally comes with ARRI Wide Gamut 4; Sony S-Log3 with S-Gamut3 or S-Gamut3.Cine; Blackmagic Film Gen 5 with Blackmagic Wide Gamut in the matching colour-science generation. In CST, Input Gamma without the correct Input Colour Space is only half the source description.
ARRI LogC4 is part of REVEAL Color Science for the ALEXA 35 generation. The official specification defines the LogC4 curve and AWG4 primaries, with AWG4 using D65 white. An important production detail is that LogC4 uses the same tonal curve across EI settings, while exposure interpretation and metadata live in the wider camera pipeline.
Sony distributes S-Log3 with different S-Gamut variants. S-Gamut3.Cine is designed to be convenient for cinematic grading and is slightly wider than DCI-P3, while S-Gamut3 is wider and requires more careful colour conversion. The label 'S-Log3' without knowing which gamut was selected is therefore insufficient for a correct transform.
Blackmagic Generation 5 Color Science uses its own wide-gamut/non-linear camera representation to preserve a large dynamic range and colour data. In Resolve, Blackmagic Film/Gen 5 options should not be replaced by older generations merely because both images look flat: the generation and camera metadata determine the correct interpretation.
RAW stores sensor data or a representation close to it before some image-processing decisions; Log is a defined RGB/video encoding after or within part of the camera colour pipeline. BRAW can be decoded into different gamma/gamut states including Film, while ProRes Log is already recorded in a specific encoding. '12-bit RAW' and '10-bit Log' therefore describe different layers of the system and are not interchangeable properties.
First identify the exact source pair: camera gamut + log curve + generation/version. Then convert the footage into the chosen working space through RCM/ACES input transforms or CST. Creative contrast, saturation and look are built after technical normalisation — or inside a scene-referred working space before the output transform. A display LUT can be useful for monitoring, but a LUT should not replace knowledge of the source state.
A wide latitude does not mean infinite headroom. The sensor still has a noise floor and clipping point; the chosen EI/ISO, lighting ratio and placement of skin/highlights affect signal-to-noise and available headroom. Log only encodes the captured range — it cannot restore what the sensor has already clipped or buried in noise.
In Resolve, never identify Log by appearance. Start with camera model/settings/metadata → determine the exact Input Colour Space + Input Gamma pair → only then apply the transform.
Technical definitions are anchored to standards bodies and primary specifications wherever that distinction matters.
Official LogC4 and ARRI Wide Gamut 4 specification.
Official Sony package with technical summary and LUT resources.
Explanation of S-Gamut / S-Gamut3 / S-Gamut3.Cine differences.
Official description of Generation 5 Color Science and non-linear camera encoding.
