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Author Topic: ProPhoto RGB vs Melissa RGB  (Read 3376 times)

texshooter

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ProPhoto RGB vs Melissa RGB
« on: August 23, 2022, 04:35:29 am »

If I'm not mistaken, Lightroom uses an exotic version of ProPhoto RGB (called Melissa RGB) as its working color space.  Prophoto RGB uses a 1.8 tonal response curve and Melissa RGB uses a 2.2 curve.  Where can I find this Melissa RGB color space to install inside Photoshop (just like I would for Beta RGB)?
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francois

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Re: ProPhoto RGB vs Melissa RGB
« Reply #1 on: August 23, 2022, 05:34:05 am »

Not sure if this is what you're looking for but there's a Melissa RGB profile here.
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Francois

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Re: ProPhoto RGB vs Melissa RGB
« Reply #2 on: August 23, 2022, 06:33:58 am »

Melissa RGB is the only used for the Histogram sans soft proffing. It is not used for any processing. ProPhoto RGB primaries with an sRGB TRC not a simple gamma curve.
http://digitaldog.net/files/18Color%20Management%20in%20Lightroom.pdf
« Last Edit: August 23, 2022, 06:44:29 am by digitaldog »
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simon.garrett@iee.org

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Re: ProPhoto RGB vs Melissa RGB
« Reply #3 on: August 23, 2022, 07:49:40 am »

Lightroom uses a whole raft of different colour spaces in different circumstances.

The working space in Develop module is ProPhoto RGB with a linear TRC.
Library module uses Adobe RGB (and previews are stored in Adobe RGB). This is to minimise step size with 8-bit previews. 
As Andrew says, Melissa RGB is used for histograms (to give a more perceptually uniform histogram).
Web module uses sRGB. 

There's no choice about any of these.  I think this is an advantage: with no settings to get wrong, it just works.  If colours vary between Lightroom and any other software, then almost invariably in my experience Lightroom is right and the other software wrong. 
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Arlen

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Re: ProPhoto RGB vs Melissa RGB
« Reply #4 on: August 23, 2022, 02:03:15 pm »

Lightroom uses a whole raft of different colour spaces in different circumstances.

The working space in Develop module is ProPhoto RGB with a linear TRC.
Library module uses Adobe RGB (and previews are stored in Adobe RGB). This is to minimise step size with 8-bit previews. 
As Andrew says, Melissa RGB is used for histograms (to give a more perceptually uniform histogram).
Web module uses sRGB. 

There's no choice about any of these.  I think this is an advantage: with no settings to get wrong, it just works.  If colours vary between Lightroom and any other software, then almost invariably in my experience Lightroom is right and the other software wrong.

Thank you, Simon, that is interesting information. I wasn't aware that the color space for LR Library module was different from the Develop module. I think that explains a perplexing observation that I made recently. Some very saturated, deep red flowers consistently showed different colors when the same image was viewed in Library mode than it did in Develop mode, as if the colors were out of gamut for Library mode. Opening the image into PS, with working color space Prophoto RGB, yielded colors matching LR's Develop mode. Now I understand why, I think.
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simon.garrett@iee.org

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Re: ProPhoto RGB vs Melissa RGB
« Reply #5 on: August 23, 2022, 02:21:41 pm »

I think that explains a perplexing observation that I made recently. Some very saturated, deep red flowers consistently showed different colors when the same image was viewed in Library mode than it did in Develop mode, as if the colors were out of gamut for Library mode. Opening the image into PS, with working color space Prophoto RGB, yielded colors matching LR's Develop mode. Now I understand why, I think.

That's my experience too.  Wide gamut monitors often go a bit beyond Adobe RGB, and test images with 100% saturated primaries in ProPhoto RGB look more vibrant in Develop module compared to Library.  I've not noticed any difference with any natural images. 
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digitaldog

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Re: ProPhoto RGB vs Melissa RGB
« Reply #6 on: August 23, 2022, 03:27:27 pm »

I wasn't aware that the color space for LR Library module was different from the Develop module.
The preview architecture differs in all modules from Develop. They use JPEGs in Adobe RGB, again, this has nothing to do with the underlying processing color space which again differs from the Histogram color space.
The most accurate way to see the data is in Develop module at 1:1 or greater zoom.
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Arlen

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Re: ProPhoto RGB vs Melissa RGB
« Reply #7 on: August 23, 2022, 03:37:18 pm »

Thanks, Andrew. I knew that the Develop view was more accurate. I just hadn't noticed before that the colors occasionally differ in Library mode on my wide gamut monitor.
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digitaldog

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Re: ProPhoto RGB vs Melissa RGB
« Reply #8 on: August 23, 2022, 03:43:11 pm »

Thanks, Andrew. I knew that the Develop view was more accurate. I just hadn't noticed before that the colors occasionally differ in Library mode on my wide gamut monitor.
Anything outside of Adobe RGB (1998) color gamut on a wide(er) gamut display will be clipped to Adobe RGB (1998) and further, the previews are JPEGs so there's whatever that brings to the party at 1:1 or greater.
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texshooter

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Re: ProPhoto RGB vs Melissa RGB
« Reply #9 on: August 23, 2022, 04:52:39 pm »

Opening the image into PS, with working color space Prophoto RGB, yielded colors matching LR's Develop mode. Now I understand why, I think.

I would think they should look different because the Develop mode in Lightroom delivers 2.2 TRC (or more precisely "sRGB TRC" which is almost identical to 2.2) whilst Prophoto RGB in Photoshop delivers 1.8 TRC.  Or does Lightroom convert 2.2 to 1.8 when going to Photoshop and, conversely, from 1.8 to 2.2 when making a round trip back into Lightroom?
« Last Edit: August 23, 2022, 05:19:46 pm by texshooter »
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digitaldog

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Re: ProPhoto RGB vs Melissa RGB
« Reply #10 on: August 23, 2022, 05:21:20 pm »

I would think they should look different because the Develop mode in Lightroom delivers 2.2 TRC (or more precisely "sRGB TRC" which is almost identical to 2.2) whilst Prophoto RGB in Photoshop delivers 1.8 TRC.  Or does Lightroom convert 2.2 to 1.8 when going to Photoshop and, conversely, from 1.8 to 2.2 when making a round trip back into Lightroom?
Thanks to Display Using Monitor Compensation, they match as they should.
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texshooter

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Re: ProPhoto RGB vs Melissa RGB
« Reply #11 on: August 23, 2022, 06:07:46 pm »

Thanks to Display Using Monitor Compensation, they match as they should.

I can't fine the DUMC checkbox.



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digitaldog

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Re: ProPhoto RGB vs Melissa RGB
« Reply #12 on: August 23, 2022, 06:17:56 pm »

I can't fine the DUMC checkbox.
Long gone (from old versions such as Photoshop 5). There's no reason to disable this.
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texshooter

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Re: ProPhoto RGB vs Melissa RGB
« Reply #13 on: September 07, 2022, 07:30:48 pm »

Not sure if this is what you're looking for but there's a Melissa RGB profile here.

The icc download includes two versions of Melissa RGB--MelissaRGB and MelissaRGBD65.  Which one is the same used in Lightroom?  And is there a reason why Adobe chose to give Melissa RGB a 2.4 TRC (same as sRGB) instead of a 2.2 TRC (same as Prophoto RGB and Adobe RGB)?
« Last Edit: September 07, 2022, 07:35:42 pm by texshooter »
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digitaldog

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Re: ProPhoto RGB vs Melissa RGB
« Reply #14 on: September 07, 2022, 07:42:46 pm »

The icc download includes two versions of Melissa RGB--MelissaRGB and MelissaRGBD65.  Which one is the same used in Lightroom?  And is there a reason why Adobe chose to give Melissa RGB a 2.4 TRC (same as sRGB) instead of a 2.2 TRC (same as Prophoto RGB and Adobe RGB)?
You can see exactly what ProPhoto RGB is and you can modify it to Melissa RGB (albeit with a simplifed gamma, not a 2.2 TRC) directly in Photoshop's Color Settings. Alter the gamma, Save As a new ICC profile. And as you can see, it isn't D65 nor can I understand why anyone would do that.
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texshooter

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Re: ProPhoto RGB vs Melissa RGB
« Reply #15 on: September 07, 2022, 07:54:03 pm »

I use Windows. I don't see your Custom RGB screen when I open Photoshop's Color Settings?
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digitaldog

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Re: ProPhoto RGB vs Melissa RGB
« Reply #16 on: September 07, 2022, 08:11:57 pm »

I use Windows. I don't see your Custom RGB screen when I open Photoshop's Color Settings?
Its there:
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texshooter

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Re: ProPhoto RGB vs Melissa RGB
« Reply #17 on: September 07, 2022, 08:25:51 pm »

Oh wait, I think I figured it out. I need to first select ProPhoto RGB inside the Working Spaces>RGB box.  Then I change that same box selection to "Custom RGB" which will load the previously selected ProPhoto RGB space, but then let me tweak the gamma curve settings. I mistakenly thought that when I selected "Custom RGB" I was removing the previously selected working space.

Sometimes finding the ON switch is the hardest step  :-[
« Last Edit: September 07, 2022, 08:47:58 pm by texshooter »
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texshooter

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Re: ProPhoto RGB vs Melissa RGB
« Reply #18 on: September 08, 2022, 12:34:40 am »

If I wanted to tweak ProPhoto RGB inside Photoshop to match exactly with Melissa RGB in Lightroom, can I choose these color settings? or does the sRGB TRC only work with the sRGB color space?



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digitaldog

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Re: ProPhoto RGB vs Melissa RGB
« Reply #19 on: September 08, 2022, 08:54:12 am »

Gamma in that dialog is simplified, not a TRC. Not identical to sRGB (not that when the rubber hits the road it will make much of a difference depending on what you do with the profile).
http://digitaldog.net/files/LinearityandGamma.pdf
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