Some software have the ability to convert from/to Cineon logarithmic space to linear. It also appears that Blender had a node named log2lin in some point (in 2.4 maybe).

Is there a way, addon or node group that can make the conversion? And the opposite?

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    $\begingroup$ There are a near infinite number of logs. Which log? Also, sRGB is a colour space, "log" is not. You would need more information. $\endgroup$ – troy_s Mar 15 '17 at 22:05
  • $\begingroup$ You were right, I've improved my question. $\endgroup$ – Antonio Buch Mar 16 '17 at 10:41

If you intend to transform a log encoded image to scene referred linear, you need to be certain of the following characteristics:

  1. The log encoding format of your source footage. There are many different log encoding formats, and to achieve a proper transform, the exact log encoding, with variables, must be known.
  2. The source footage colour primaries. The source is encoded with specific colour primaries that must be known.
  3. The destination colour primaries. These must be known to transform to your reference correctly. Blender's default configuration reference space assumes BT.709 primaries, for example.
  4. The destination transfer characteristics. In the case of default Blender, the reference space in the compositor is scene referred linear.

Once you know these details, the proper transforms can be added to the OpenColorIO configuration, and your data can be transformed correctly.

| improve this answer | |
  • $\begingroup$ Excuse me, but I do not understand how to convert the images. $\endgroup$ – Antonio Buch Mar 21 '17 at 12:23
  • $\begingroup$ You would need to identify specifically what log encoding format the encoded values are in, as well as what colours the primary lights, or primaries are. That is "What colours do the red, green, and blue intensity values represent?" $\endgroup$ – troy_s Mar 21 '17 at 12:26
  • $\begingroup$ Yeah, it's Cineon log. Software like AE or Natron have an effect/node to convert from/to Cineon log. $\endgroup$ – Antonio Buch Mar 22 '17 at 9:19
  • $\begingroup$ What are the primaries? $\endgroup$ – troy_s Mar 22 '17 at 9:19
  • $\begingroup$ How can I find out what the primaries are? Sorry for the initial question troy_s but I think that my improved question focus only on Cineon log which is a standard format. Your answer only leads to more questions, how can I identify the primaries? How to add the transforms to the OpenColorIO configuration? Could you focus on Cineon or improve your answer to a more step to step one? $\endgroup$ – Antonio Buch Mar 22 '17 at 9:43

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