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Gamma shift with LUTs in Coremelt’s Chromatic
Has anyone else noticed that Coremelt’s new plugin, Chromatic, makes a brighter picture compared to CGC finale or LUT utility (or mLUT!) when using the same LUT in both?
It looks to me like a gamma shift. I find I can get things to match by dragging the gamma slider in Chromatic from the default 2.40 to around 1.95. It is a shame that this slider is not available for the Camera log section though.
I guess the question is, which plugin is right?
Most of my LUT’s come from the brilliant LUTCalc and I deal with a lot of sony Slog3cine footage.
I am using the recommended legal/legal data range (as listed for FCPx and LUT utility/finale)I have to say this plugin is so good in every other respect, but if it is indeed increasing gamma… that is not good:-(
Maybe I’ve been living with darker pictures for ages and just got used to it!I messaged Coremelt tech support ten days ago and got no response. grrr
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10 Replies
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is that product still in public beta?
Scott Witthaus
Owner, 1708 Inc./Editorial
Managing Partner, Low Country Creative LLC
Professor, VCU Brandcenter -
Did you try hitting them all up over Twitter- sounds like an intriguing issue.
Noah
FCPWORKS – FCPX Workflow
FCP Exchange – FCPX Workshops
XinTwo – FCPX Training -
[Scott Witthaus] “is that product still in public beta?”
No. It’s been out commercially for a bit.
– Oliver
Oliver Peters – oliverpeters.com
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[Thomas O'Carroll] “I guess the question is, which plugin is right?”
The short answer is to not use LUTs. Many apps interpret them differently and their creation is either subjective or reverse engineered by the developer. I frequently see differences between the results of FCPX’s internally applied LUTs for camera profiles and LUTs that are theoretically the same, from other sources, applied elsewhere within the pipeline. It’s a color science issue and each developer handles it differently. So all may be correct or incorrect. Unfortunately it’s not an exact science.
– Oliver
Oliver Peters – oliverpeters.com
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I played around a bit more with this today using some Alexa Mini footage. I noticed that FCPX has 2 built-in camera profile LUTs – a regular and a 3D. The regular LUT looks closer to what I see in Chromatic, with elevated gamma. However, it’s the 3D LUT that should be used and what the clip defaults to. So maybe Chromatic is not using 3D Cube LUTs.
– Oliver
Oliver Peters – oliverpeters.com
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Hmm, I ran into another issue, severe luma clamping before applying any processing. It simply hard clamped luma to 100 when applying Chromatic. Even changing their “illegal Colors” to “Do Not Clamp” had no relief.
With 24 hours after I reported it they acknowledged it. Said they believe it may be related to the specific GPU (Late 2013 Mac Pro with AMD FirePro 500 in my case). In about 3 days they had a build for me which fixed the issue.Given what you’re seeing you should send them screenshots using the same source with CG and Chromatic with only the lut applied. Include Before and After scopes as well. I’d also include the GPU just in case that’s a factor.
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Just to say thanks for your replies. Sorry if it looks I’m slow to respond.
Coremelt responded to my support request on the 24th August. They said they’d look into the issue and get back to me. I’ve not heard anything since, but we’ll see.
Just to be clear, does anyone else see the problem I’m having?
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[Thomas O'Carroll] “Just to be clear, does anyone else see the problem I’m having?”
Yes.
– Oliver
Oliver Peters – oliverpeters.com
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[Oliver Peters] “The regular LUT looks closer to what I see in Chromatic, with elevated gamma.”
Just to clarify… are you saying you see a gamma “boost” as well?
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[Thomas O'Carroll] “are you saying you see a gamma “boost” as well?”
Yes.
– Oliver
Oliver Peters – oliverpeters.com
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