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Need help understanding RedCineX Color Space and Gamma Space

Omar N

Omar N

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Hello everyone,

Can anyone provide a brief explanation on what the different options mean under the Color Space and Gamma Space in RedCine-X? I see the following:

Color Space:

REDcolor
REDcolor 2

Gamma Space:

REDgamma
REDgamma 2
REDlog
REDlog film


When I change this parameters, the look obviously gets changed but I am not sure what the meaning of each item is, or if one is "better" than the other.

I have poked around a bit on the forums but did not see this question answered. I apologize if I missed it.

Thank you very much in advance for your help.
~Omar
 
Short answer:

RedColor2
RedGamma2

I'll leave the longer explanation to someone more knowledgeable than myself :)
 
..and about to be replaced by "xxxxx3" versions!

Stu Aull
Alaska
 
Shoot in REDcolor 2
Grade in REDlog film

. . . is what I got out of REDucation
 
Color is hue, saturation and to some degree value but mostly hue and saturation.
Gamma is like curves in photoshop.

Just as you can save an image in linear, log or rec709 space and then convert back to sRGB so too can REDColor be encoded to another gamma. The one exception though is that REDLogfilm and Linear both are linear just stored differently but REDGamma isn't a standard gamma and can't be reversed.
 
Gamma and Color Space are used to interpret RAW data into something useful. They are typically used as a look for monitoring and a starting point for grading.

Over time... Graeme has been able to improve both of these. The newest (and best) will be released today... REDcolor3 and REDgamma3.

Because you are shooting RAW, files can be opened in any combination of gamma and color space that you like best. And you can change between them whenever you want. Personal preference.

IMHO, RC3 gives the best color, especially skin tones, and RG3 is the nicest "out of the box" look. (Don't forget to try adding a bit of Alchemy).

We do expect that most serious grading will still be done with RC3 and REDlogFilm.

Jim
 
Is it possible to get a linear to light for sfx, or even better, a lut to put on top of cg for vfx work.
It'd make my day:-)

Thanks
 
Jannard said:
IMHO, RC3 gives the best color, especially skin tones, and RG3 is the nicest "out of the box" look. (Don't forget to try adding a bit of Alchemy).
Click to expand...
For corporate and shorts work, what is the trick to using Alchemy to get quick solid results? How is it best used with rg2/rg3?
 
Patrik Forsberg said:
Is it possible to get a linear to light for sfx, or even better, a lut to put on top of cg for vfx work.
It'd make my day:-)

Thanks
Click to expand...

Select linear for gamma (after enabling advanced controls) or export to EXR (always linear light).
 
For linear light integer formats, it's important to set the ISO down to 320 to ensure it doesn't clip or go into non-linear FLUT gain, and remember there's a black offset of 800/65535 in the data that must be subtracted in processing to get pure linear light. But there's better ways to get linear light... Always use a 16bit format for this kind of output.

1) export EXR as Rob suggests above. That is utterly linear, no offset, never anything non-linear and no ISO/FLUT range restrictions or anything.
2) export with REDLogFilm because it linearizes perfectly back to linear light using the standard cineon equation in Nuke, Shake etc.

Graeme
 
And there you have it guys. The master explains it way better than I ever could! :)
 
Wow what a response! Thanks guys. One of the biggest reasons to shoot on RED is the support found on these forums. Seriously...
 
Omar N said:
Can anyone provide a brief explanation on what the different options mean under the Color Space and Gamma Space in RedCine-X?
Click to expand...
Color Space and Gamma Space are words that are frequently thrown around, and they can mean different things to different people. I've seen different manufacturers even not quite agree on what they are. (In particular, Quantel and Technicolor.)

At least you didn't ask about Lookup Tables (LUTs)! I came to the conclusion a long time ago that a LUT can mean almost anything you want it to mean. As long as the color being displayed on your monitor is correct, it almost doesn't matter -- a good color corrector can act as "sort of" a variable LUT, to a point.

Graeme is, of course, absolutely right: the role of the color space and gamma space controls in RedCineX Pro are there just to get you closer to what you eventually want to work with. Applying a temporary look is very necessary during the initial editing process, and is also helpful for the final colorist. I would never want anyone to have to work with RAW files where they can't see at least a semblance of what the DP initially wanted. But making those decisions with an uncalibrated monitor is dicey at best.

Good references:

Color Space

Gamma Correction

Color Management

Quantel Digital Factbook

Quantel Guide to Digital Intermediates

I would also point to Steve Shaw's Light Illusion website, as well as the many reference papers available on Northlight's website and THX/Cinespace's website. There are many different ways to approach this problem, but over the last ten years, the industry seems to be sorta/kinda moving in the same vague direction. The problem is, no two camera companies exactly agree on color science. Kodak sort of invented most of this stuff years ago, but a lot of that's been discarded (both rightly and wrongly). One hopes that SMPTE and other industry orgs will set some standards that will be widely adopted, but things are changing so fast, I'm not optimistic.

The two most important things to consider (strictly my opinion): make sure you can believe your monitor in terms of calibration, so you know it's telling you the truth; and test the workflow before you commit to a specific process. In lots of cases, you can make up your own standards, create a unique aspect ratio, do all kinds of stuff, but ultimately, it has to work for the distributor who pays for the project.
 
Just switch on Alchemy (in RCX-P) and it goes to the default of 0.35. That seems to be a nice place to start.

Jim

PatrickFaith said:
For corporate and shorts work, what is the trick to using Alchemy to get quick solid results? How is it best used with rg2/rg3?
Click to expand...
 
Patrik Forsberg said:
Is it possible to get a linear to light for sfx, or even better, a lut to put on top of cg for vfx work.
It'd make my day:-)

Thanks
Click to expand...

I have LUTs (Color .mga by default, but available in other formats) available for sale on my website (see my signature) which can be used to view/render REDlogFilm as REDgamma or REDgamma2 (I guess I'll need to create a REDgamma3 version now). In Nuke I use a lin2log followed by a 1D version of this LUT as a viewer LUT, which I find works well for me. Is this the sort of thing you are looking for?
 
Jannard said:
Just switch on Alchemy (in RCX-P) and it goes to the default of 0.35. That seems to be a nice place to start.

Jim
Click to expand...

I just shot a 2 day shoot and was told that the trans-code to Pro Res for offline took forever after day one's shoot. We set up a look for the Pro Res which included Alchemy and a small shadow adjustment.

Day two we set the Pro Res file output without the Alchemy setting and was told the files transcoded at least 50% faster than day ones.

Does the Alchemy setting make for a much more computer intensive conversion?
 
Tim Bradley said:
I just shot a 2 day shoot and was told that the trans-code to Pro Res for offline took forever after day one's shoot. We set up a look for the Pro Res which included Alchemy and a small shadow adjustment.

Day two we set the Pro Res file output without the Alchemy setting and was told the files transcoded at least 50% faster than day ones.

Does the Alchemy setting make for a much more computer intensive conversion?
Click to expand...

If there is a RR in that machine, it makes a big difference – Alchemy is not accelerated by it.
 
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