Gamma

Gamma describes the nonlinear relationship between a pixel's numerical value and the actual light output on a display. A gamma of 2.4 means that an input value of 0.5 (middle code value) produces an output of 0.5^2.4 = 0.189 — only about 19% of maximum brightness. This nonlinearity exists because human vision is roughly logarithmic: we perceive more detail in dark tones than in bright ones, so encoding more data in the shadow range makes efficient use of the available bit depth. In practical post-production, you encounter gamma in three contexts. Display gamma: the curve your monitor applies to convert input signal to light output. ITU-R Recommendation BT.1886 specifies 2.4 gamma for broadcast reference monitors in dim-surround conditions. sRGB uses a piecewise curve close to 2.2 gamma for brighter viewing environments. DCI-P3 theatrical uses 2.6 gamma for dark theaters — the darker the room, the higher the gamma needed to maintain perceptual contrast. Scene-referred gamma (LOG curves): camera manufacturers encode the sensor's linear data into logarithmic curves to preserve dynamic range. Sony S-Log3 maps 14+ stops into a 10-bit signal with a mid-gray point at 41% IRE (code value ~420 in 10-bit). Canon C-Log3 places mid-gray at ~34% IRE. Blackmagic BRAW Film uses a custom curve similar to Rec.709 in the highlights but with extended shadow rolloff. These LOG curves are not viewable as-is — they need to be converted (via a LUT, CST, or color management) to a display-referred gamma for monitoring. The reason gamma matters more than most colorists think: changing the display gamma changes the apparent contrast, shadow density, and color saturation of every image. A grade that looks perfect on a 2.4 gamma broadcast monitor will look flat and washed out on a 2.2 gamma computer screen, and crushed on a 2.6 gamma theatrical projector. You are not grading pixels — you are grading light output, and gamma is the translation layer between the two.

The most common gamma disaster: mixing scene-referred and display-referred pipelines. Here is the classic scenario — a DIT hands you S-Log3 footage with a show LUT applied in the metadata. You view it in Resolve with the LUT enabled, grade on top of the LUT, and everything looks fine. Then the editor takes the same footage into Premiere Pro, which does not read Sony's metadata LUTs, and suddenly the footage looks completely washed out because Premiere is interpreting LOG data as if it were Rec.709 display-referred. The grade cannot be matched because the gamma interpretation is fundamentally different between the two NLEs. LOG gamma curves differ between manufacturers, and there is no universal LOG. ARRI LogC4 has a different curve shape, mid-gray point, and shadow rolloff than Sony S-Log3 or Panasonic V-Log. If you apply a S-Log3-to-Rec.709 LUT to LogC4 footage, the mid-gray shifts, the highlights clip differently, and skin tones go wrong by 10-15 degrees on the vectorscope. Always use manufacturer-specific CST (Color Space Transform) conversions, not generic LOG-to-Rec.709 LUTs. In Resolve, the CST OFX plugin lets you specify exact input and output gamma curves — use it instead of LUTs for any critical work. Quick gamma reference for monitoring: use 2.2 for bright rooms (web content, office viewing), 2.4 for controlled dim environments (broadcast QC, client review suites), and 2.6 for theatrical projection. If you are delivering HDR, the gamma concept is replaced by the PQ (Perceptual Quantizer) transfer function defined in SMPTE ST 2084, which is absolute — it maps code values directly to nits of brightness rather than using a relative gamma curve. The entire 10-bit range maps from 0.0001 to 10,000 nits in a perceptually uniform way, with nominal diffuse white (100 nits) landing near the middle of the curve.