SDI Color Space setting

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calebstaines
Posts: 1
Joined: Sun May 08, 2016 2:49 am

Hi,

I have some questions about the SDI Color Space setting in the Look menu of the LF and Mini LF (and some other older models). I’ve done a little research and can’t find an explanation anywhere. I feel like I'm misunderstanding something.

In the section describing the SDI Color Space setting, the Mini LF User Manual gives a good explanation of what Rec. 709 and Rec. 2020 are but it doesn’t really explain what this setting does, when it has an effect and why you would want to change it.

Say I’ve created an ALF-2 file with a LUT which includes a colour space transform to Rec. 709 / BT. 1886. If the SDI Color Space in camera is set to Rec. 2020, does this transform the SDI output signal so that the image will display correctly on a Rec. 2020 monitor?

Say I’ve created a different ALF-2 file which targets DCI-P3. Does the SDI Color Space setting have an effect in this case? Or does the camera know that the target colour space of the ALF-2 file is not Rec. 709 or Rec. 2020 and therefore that the adjustment isn’t appropriate? Does the ALF-2 file contain metadata about the target colour space based on the setting in the Arri Color Tool when the Look file was made?

If I’m outputting LogC3 over SDI, does the SDI Color Space setting have an effect on the outputted signal? I feel like it shouldn’t. I know I could test this myself but I never seem to get around to experimenting with these things during a shoot day.

The pipeline of the Alexa 35 seems more straightforward. The ALF4 file is always targeting LogC4 and the SDI Color Space setting is choosing which display transform is applied. (Right?) But its function in the older cameras isn’t so clear; the selected Look or Look file is already targeting a particular display standard so what is this setting for?

Any clarification would be really appreciated.

Caleb Staines
DIT
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