Colour spaces

Simulator

Raw formats

Raw keeps the sensor's own data instead of a finished picture, so white balance, ISO and the colour pipeline can still be chosen afterwards. Video raw formats are built to be played back frame after frame and usually develop into the maker's log curve and gamut. Still raw formats keep one frame at the highest bit depth the sensor gives.

Gamut, gamma and what a LUT moves

Two different things decide how a camera stores colour: which colours it can reach at all, and how it spreads brightness across the numbers in the file. They are chosen separately, and confusing them is behind most of the trouble people have with log footage.

• Gamut is the range of colour

  A colour space is a triangle drawn between three primaries. Everything inside it can be described by mixing them; everything outside simply cannot be represented, however many bits you have. Rec.709 is a small triangle, Rec.2020 a much larger one.

• Rec.709

  The television standard, and still what most screens and most delivery specs assume. Its triangle is small, which is why heavily saturated reds and greens from a wide-gamut camera have to be pulled in to fit.

• DCI-P3

  The cinema projection standard, and what most modern phones and laptops actually display. Noticeably wider than Rec.709 in the reds and greens, and the realistic target for anything that needs to look rich on good screens.

• Rec.2020

  The ultra-high-definition standard. Wider than any current display can actually show, so it is used as a container to work in rather than something a screen reproduces. Much of its triangle is theoretical today.

• Gamma is not gamut

  Two separate things that get confused constantly. Gamut is which colours you can reach. Gamma, or the transfer curve, is how brightness is spread across the numbers in the file. A camera has both, and they are chosen independently.

• Why log looks flat

  A log curve spreads the code values evenly across the stops so that no part of the range is starved. Shown directly on a screen expecting a display curve, that looks washed out and grey. It is not a look, it is storage.

• What a LUT does

  A lookup table maps one set of values onto another: usually log footage into a display standard so it can be judged. A viewing LUT changes nothing in the file. A LUT baked into a render does, and cannot be taken back out.

• Raw is linear

  A sensor counts light, so raw data is linear: each stop up doubles the number. Half of all the code values go to the brightest stop and the darkest stops get a handful, which is why still raw needs 12 to 16 bits where a log file manages with 10.

• Raw has no colour space yet

  Raw values are in the sensor's own colours, which no standard describes. Developing the file turns them into a gamut: for video usually the maker's own wide gamut, which reaches further than Rec.2020 and sometimes outside the colours the eye can see.

• The practical order

  Shoot in the widest gamut and the log curve your camera offers, grade in a wide working space, and convert to the delivery standard last. Converting early throws away range you cannot get back.