Scene-Linear to Shaper + LUT with 3DL file format

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Amaan Akram

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Aug 28, 2018, 12:52:01 PM8/28/18
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Hi all,

I've been using the Cinespace lut format with ociobakelut to make LUTs that go from Scene-Linear -> AlexaV3LogC -> Shot LUT.

This has worked just fine for 99% of our needs. Now, however, I need to use the .3DL Flame format but the transform going from Scene-Linear->ShaperLUT does not seem to handle input values above 1.
The only change in the command for ociobakelut is the change of format from cinespace to flame. I assume there is something very simple that I am missing. Has anyone run into this before?

thank you,
amaan


Kevin Wheatley

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Aug 28, 2018, 12:57:28 PM8/28/18
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On Tue, Aug 28, 2018 at 2:20 PM, Amaan Akram <am...@themill.com> wrote:
> I've been using the Cinespace lut format with ociobakelut to make LUTs that
> go from Scene-Linear -> AlexaV3LogC -> Shot LUT.
>
> This has worked just fine for 99% of our needs. Now, however, I need to use
> the .3DL Flame format but the transform going from Scene-Linear->ShaperLUT
> does not seem to handle input values above 1.

Amaan,

From your description, I suspect your problem is simply assuming the
3DL format can handle input >1.0 which in general implementations they
do not (there are some but they are obscure).

What is preventing you sticking with CSP files? You should be able to
use them with Flame for instance, or is it a different tool that is
forcing you to the Flame format?

Kevin

Amaan Akram

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Aug 28, 2018, 1:00:57 PM8/28/18
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Thanks Kevin

Indeed I am assuming that the Shaper LUT can map [0-8] back to [0-1] for 3DL

I am trying to use ffmpeg, which does not support Cinespace LUTs, but does support Iridas Cube, Pandora and 3DL

Kevin Wheatley

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Aug 28, 2018, 1:10:21 PM8/28/18
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How are you feeding images with the range 0-8 into FFmpeg as OpenEXR?

If so you could use the conversion functions supported by the
apply_trc option from the OpenEXR codec, as a preshaper, then you
could use the 3DLUT as [0-1]. FFmpeg doesn't really work outside the
0-1 range, it is designed around the use of integer encoding and the
floating point support is currently limited.

You would then need to edit your OCIO config to emulate the same
shaper functions (SMPTE 2084 or maybe one of the log functions would
work for you), so your ociobakelut output would work for you

yes it is a bit of a hack

Kevin

Amaan Akram

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Aug 29, 2018, 4:43:11 AM8/29/18
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Thanks Kevin. Unfortunately none of those log functions apply to our case. We will investigate a different route.
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