FORUMS: list search recent posts

Gamma shift with LUTs in Coremelt's Chromatic

COW Forums : Apple Final Cut Pro X

<< PREVIOUS   •   VIEW ALL   •   PRINT   •   NEXT >>
Thomas O'Carroll
Gamma shift with LUTs in Coremelt's Chromatic
on Aug 22, 2017 at 12:21:37 pm

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


Return to posts index

Scott Witthaus
Re: Gamma shift with LUTs in Coremelt's Chromatic
on Aug 22, 2017 at 2:25:31 pm

is that product still in public beta?

Scott Witthaus
Owner, 1708 Inc./Editorial
Managing Partner, Low Country Creative LLC
Professor, VCU Brandcenter


Return to posts index

Oliver Peters
Re: Gamma shift with LUTs in Coremelt's Chromatic
on Aug 22, 2017 at 2:46:56 pm

[Scott Witthaus] "is that product still in public beta?"

No. It's been out commercially for a bit.

- Oliver

Oliver Peters - oliverpeters.com


Return to posts index


Noah Kadner
Re: Gamma shift with LUTs in Coremelt's Chromatic
on Aug 22, 2017 at 2:26:02 pm

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


Return to posts index

Oliver Peters
Re: Gamma shift with LUTs in Coremelt's Chromatic
on Aug 22, 2017 at 2:52:53 pm

[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


Return to posts index

Oliver Peters
Re: Gamma shift with LUTs in Coremelt's Chromatic
on Aug 22, 2017 at 10:11:22 pm

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


Return to posts index


Thomas O'Carroll
Re: Gamma shift with LUTs in Coremelt's Chromatic
on Sep 1, 2017 at 3:02:01 pm

[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?


Return to posts index

Oliver Peters
Re: Gamma shift with LUTs in Coremelt's Chromatic
on Sep 1, 2017 at 3:20:35 pm

[Thomas O'Carroll] "are you saying you see a gamma "boost" as well?"

Yes.

- Oliver

Oliver Peters - oliverpeters.com


Return to posts index

Craig Seeman
Re: Gamma shift with LUTs in Coremelt's Chromatic
on Aug 23, 2017 at 2:07:35 am

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.



Return to posts index


Thomas O'Carroll
Re: Gamma shift with LUTs in Coremelt's Chromatic
on Sep 1, 2017 at 2:54:32 pm

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?


Return to posts index

Oliver Peters
Re: Gamma shift with LUTs in Coremelt's Chromatic
on Sep 1, 2017 at 3:01:48 pm

[Thomas O'Carroll] "Just to be clear, does anyone else see the problem I'm having?"

Yes.

- Oliver

Oliver Peters - oliverpeters.com


Return to posts index

<< PREVIOUS   •   VIEW ALL   •   PRINT   •   NEXT >>
© 2017 CreativeCOW.net All Rights Reserved
[TOP]