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Video basics3 min read

LESSON 87

Log profiles and LUTs

Flat on purpose, then shaped later.

IN THIS LESSON

  1. What a log profile is
  2. Where log came from
  3. What a LUT is
  4. Practice: working with log

What a log profile is

A log profile is a picture setting that records brightness on a logarithmic curve rather than the contrasty curve of normal video. The result looks grey and washed out straight from the camera, but it keeps detail in the shadows and highlights that a normal profile would throw away. The flat image is not meant to be watched as it is. It is a starting point for colour grading, where the contrast and colour are put back in a controlled way. Log is used mostly in filmmaking and higher-end videography.

Where log came from

The idea goes back to Kodak's Cineon film-scanning system of the early 1990s, which used a log curve to store scanned negatives efficiently. Digital cinema cameras adopted it: Arri's D-20 offered Log-C around 2005, and Sony's F35 recorded S-Log in 2008. Cheaper cameras followed, including Canon Log on the C300 and S-Log2 on Sony's A7 II. Each maker has its own curve, among them Log-C on Arri, C-Log on Canon, F-Log on Fujifilm, N-Log on Nikon, S-Log on Sony, V-Log on Panasonic and D-Log on DJI drones. They are not interchangeable.

What a LUT is

A lookup table, or LUT, is a table that maps each input colour to an output colour. A 3D LUT is a cube of values indexed by red, green and blue, and the software blends between the nearest points; cubes of 33 points per side are common. In practice a LUT is how a flat log picture is turned into something that looks normal on a monitor, or how a planned look is previewed on set. LUTs are used throughout film production and in the digital intermediate, and modern graphics cards and many monitors can apply them in real time.

Practice: working with log

This is working practice. Expose log carefully, because its flat look fools the eye: use the maker's recommended middle-grey level or a conversion LUT on the monitor while you shoot. Load the maker's conversion LUT for your exact log curve, not a random creative one. In the edit, apply the conversion first and grade on top of it. If you have little time or will not grade, a standard profile may serve you better than log. Keep a note of which curve and which LUT each clip used, because a LUT built for one maker's log will give strange colour on another's, and the mistake is easy to miss on a small screen.

Try it today

  1. 01Find which log curve your camera uses and download the maker's LUT.
  2. 02Shoot one scene in log and one in the standard profile.
  3. 03Apply the conversion LUT to the log clip in your editor.
  4. 04Lift shadows and pull highlights on both clips and compare.
  5. 05Save the LUT where your editor will always find it.