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Author Topic: Lightroom Colour Space  (Read 7760 times)

papa v2.0

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Lightroom Colour Space
« on: February 23, 2015, 07:42:53 pm »


I apologise it this has been done to death.
so if there is a thread ive missed just say so.

When I open a RAW in LR what space am I rendering in (Melissa/Prophoto?)
When I export (say to sRGB) does the colour space conversion take place then (clipping and all)?

Ta
Iain



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digitaldog

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Re: Lightroom Colour Space
« Reply #1 on: February 23, 2015, 07:53:03 pm »

When I open a RAW in LR what space am I rendering in (Melissa/Prophoto?)
When I export (say to sRGB) does the colour space conversion take place then (clipping and all)?
Yes and no. Yes, you are clipping at the point of conversion. No, it's not Melissa or ProPhoto RGB. Close, same gamut and primaries, different TRC. Has no name (Melissa is used for Histograms and RGB numbers).
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Jim Kasson

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Re: Lightroom Colour Space
« Reply #2 on: February 23, 2015, 08:28:08 pm »

Yes and no. Yes, you are clipping at the point of conversion. No, it's not Melissa or ProPhoto RGB. Close, same gamut and primaries, different TRC. Has no name (Melissa is used for Histograms and RGB numbers).

Andrew is, as usual, correct. The only thing I can add is that the tone response curve is linear -- some would say it's not a curve at all -- in Lr's native space. That makes a lot of operations less expensive (in terms of machine cycles) to execute.

Jim

papa v2.0

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Re: Lightroom Colour Space
« Reply #3 on: February 24, 2015, 04:28:21 am »

Hi Andrew, Jim . Thanks  to both.

I was thinking that was the case.

So the histogram is based on a rendering to Melissa which is a variant of ProPhoto.

There is no ability in LR to render directly to a smaller space with associated histogram, is that correct?

Unlike Camera Raw where one can select the render-space (choice of four) and the associated histogram before export.

Also, has the image on screen gone thought the selected colour space choice for export (say sRGB) or is it a straight internal colour space to monitor colour space conversion. (hope that makes sense).

and last but not least, why histogram readout in RGB% and can this be changed to RGB 255 etc

Iain



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D Fosse

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Re: Lightroom Colour Space
« Reply #4 on: February 24, 2015, 05:30:48 am »

In soft proof the corresponding histogram is shown. In fact you can think of ACR as Lightroom with soft proof permanently on.

The on-screen image is always the standard source profile > display profile conversion.* In Develop the source is linear ProPhoto; for the Library previews the source is Adobe RGB. This, incidentally, is why a broken monitor profile can show up differently between the two modules.

In soft proof you have a 0 to 255 readout. It only makes sense in soft proof, where the numbers correspond to an actual color space. But you can get Lab numbers if that's any help.

*edit: Obviously, soft proof also limits display gamut by inserting the proof profile into the chain. But unless your monitor is wide gamut and you're proofing to sRGB, you won't see any difference on screen. The monitor color space is usually the limiting one.
« Last Edit: February 24, 2015, 06:43:30 am by D Fosse »
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papa v2.0

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Re: Lightroom Colour Space
« Reply #5 on: February 24, 2015, 07:04:31 am »

Thanks D

Its all clear now.  I was assuming that the same space was used for library and develop.

"In Develop the source is linear ProPhoto; for the Library previews the source is Adobe RGB. This, incidentally, is why a broken monitor profile can show up differently between the two modules"



Or a badly made monitor profile or a crap monitor can compound things.   

Cheers.

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digitaldog

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Re: Lightroom Colour Space
« Reply #6 on: February 24, 2015, 10:09:56 am »

I was assuming that the same space was used for library and develop.
For the processing of the data it is the same. For previews, it's different (frustrating design).
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bjanes

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Re: Lightroom Colour Space
« Reply #7 on: February 24, 2015, 11:06:50 am »

Unlike Camera Raw where one can select the render-space (choice of four) and the associated histogram before export.

In the more recent versions of ACR one can render into any number of color spaces, including L*a*b and even one's monitor space or printer space as shown in the screen capture below.

Also, has the image on screen gone thought the selected colour space choice for export (say sRGB) or is it a straight internal colour space to monitor colour space conversion. (hope that makes sense).

and last but not least, why histogram readout in RGB% and can this be changed to RGB 255 etc

The tone curve used for the readouts is merely a normalized sRGB tone curve converted from 0..255 to 0..1. To demonstrate this, I used Photoshop's posterize command to prepare a sRGB file with 10 monochrome levels and used Photoshop's info to read out the sRGB values. I then imported the file into Lightroom and read out the values as percentages and then converted the percentages back to 0..255 by multiplying by 255 as shown in the Excel spreadsheet below.

For a color image, the process would be more complicated, since the primaries in LR are those of ProPhotoRGB.

Bill

« Last Edit: February 24, 2015, 11:11:05 am by bjanes »
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Jim Kasson

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Re: Lightroom Colour Space
« Reply #8 on: February 24, 2015, 11:10:04 am »

Yes and no. Yes, you are clipping at the point of conversion. No, it's not Melissa or ProPhoto RGB. Close, same gamut and primaries, different TRC. Has no name (Melissa is used for Histograms and RGB numbers).

Warning: this post is of interest only to image processing nerds.

When I write image processing code, my go-to representation for RGB color planes is double precision floating point, with the nominal black point 0,0,0 and the nominal white point 1,1,1. However, where it makes sense, and most of the time it does, I allow values below 0 and those above 1. This is especially useful in intermediate calculations. I suspect that Lr does something similar, although I'd expect them to use single precision (32-bit) floating point. Eric Chan, if you see this, could you set me straight?

If that's true, then the gamut of the Lr native color space is not limited to the gamut of PPRGB, since negative values would allow the gamut to be extended without limit to include even more nonphysical triplets and some that actually correspond to visible colors.

Jim

papa v2.0

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Re: Lightroom Colour Space
« Reply #9 on: February 24, 2015, 11:51:40 am »

Im downloading PS cc as we speak.
I was using PS CS6 ACR re the four colour spaces.

Thanks Jim

and yes Andrew frustrating design and for the guys in my local camera club, its really confusing as well. They still havent got to grips with digital yet re the colour  profiles.

They all have CC LR and PS but moan when nothing comes out right!

A colour scientists work is never done!

Iain
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Simon Garrett

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Re: Lightroom Colour Space
« Reply #10 on: February 24, 2015, 01:04:56 pm »

Warning: this post is of interest only to image processing nerds.

When I write image processing code, my go-to representation for RGB color planes is double precision floating point, with the nominal black point 0,0,0 and the nominal white point 1,1,1. However, where it makes sense, and most of the time it does, I allow values below 0 and those above 1. This is especially useful in intermediate calculations. I suspect that Lr does something similar, although I'd expect them to use single precision (32-bit) floating point. Eric Chan, if you see this, could you set me straight?

If that's true, then the gamut of the Lr native color space is not limited to the gamut of PPRGB, since negative values would allow the gamut to be extended without limit to include even more nonphysical triplets and some that actually correspond to visible colors.

Jim


Interesting thought. 

To me that seems similar to the benefit of editing even an sRGB image in a wide working space.  An sRGB image has no colours beyond its colour space but intermediate results of processing calculations might go beyond (and of course if you edit in a wide colour space you could create additional colours by screwing up the saturation!)
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Tim Lookingbill

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Re: Lightroom Colour Space
« Reply #11 on: February 24, 2015, 02:12:27 pm »

For the processing of the data it is the same. For previews, it's different (frustrating design).

You too, huh?

In LR4.4 having to turn on Soft Proof just to get 1.8 gamma ProPhotoRGB (my output space) histogram and RGB readouts is so annoying. And right behind it in annoyance is the subsequent warning dialog box after making the first edit asking if I want to make this the Proof or Proof Copy which I have no idea what the differences are.
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digitaldog

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Re: Lightroom Colour Space
« Reply #12 on: February 24, 2015, 04:04:07 pm »

You too, huh?
Yes but not as you understand what I wrote.
Quote
In LR4.4 having to turn on Soft Proof just to get 1.8 gamma ProPhotoRGB (my output space) histogram and RGB readouts is so annoying.

There's no visual difference (on this end) soft proofing either way. The numbers and Histogram change a bit due to the TRC which isn't an issue for me at all. The bkgnd will change too. The image? Not a lick.
What makes this architecture frustrating is having different behaviors for images in different modules! Having to tell people that if they suspect a preview issue with color, always be in Develop (don't necessarily bank on what you see outside that module). Also speed to render images to screen (the primarily reason I suspect we have two color spaces in different areas).
Quote
And right behind it in annoyance is the subsequent warning dialog box after making the first edit asking if I want to make this the Proof or Proof Copy which I have no idea what the differences are.
RTFM ;D
If you setup a soft proof and try to edit it, you are doing so with a new preview of the color so LR expects you to create a Proof Copy to apply it to and keep the original un-edited. Without layers, it would be folly to edit the master this way.
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Tim Lookingbill

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Re: Lightroom Colour Space
« Reply #13 on: February 24, 2015, 09:46:01 pm »

I wasn't referring to the preview change in my post, Andrew, just having to go through the trouble I indicated just to get RGB readouts and a histogram that reflects output.

I know what you meant by having two different preview setup differences between Library and Develop.

Quote
If you setup a soft proof and try to edit it, you are doing so with a new preview of the color so LR expects you to create a Proof Copy to apply it to and keep the original un-edited. Without layers, it would be folly to edit the master this way.

But switching Soft Proof to ProPhotoRGB as output in Develop module doesn't change the preview as you've said for both modules so what's your point? Or are you indicating the differences between "Make this the Proof" over "Proof Copy"? See how frickin' confusing and frustrating even talking about it is? We constantly talk at cross purposes over something as simple as Soft Proof and LR previews between two GUI's within the same app.

I'm going back to ACR 6.7 just cool off. And no, I'm not going to buy CS6 ACR which I'm sure someone was going to suggest. Oh good lord I'm so glad I'm not having to put up with this using Cloud apps. Just seeing the $10 a month reminder, update download alerts and/or seeing it on my credit card statement would set me off.
« Last Edit: February 24, 2015, 09:47:34 pm by Tim Lookingbill »
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digitaldog

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Re: Lightroom Colour Space
« Reply #14 on: February 25, 2015, 09:07:00 am »

I wasn't referring to the preview change in my post, Andrew, just having to go through the trouble I indicated just to get RGB readouts and a histogram that reflects output.
It doesn't visually change only because you insist on setting up ProPHoto RGB as a soft proof and the data you see is basically in ProPhoto RGB! If you select another color space, the preview will very likely change because you are far farther from the original and editing that data must and should be done on a VC, NOT THE MASTER!
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I know what you meant by having two different preview setup differences between Library and Develop.
We're not ready to do there yet. But the preview architecture and color spaces used are NOT the same between Develop and the other modules.
Quote
But switching Soft Proof to ProPhotoRGB as output in Develop module doesn't change the preview as you've said for both modules so what's your point?

My point is you are criticizing a behavior based on your own misunderstanding! IF you switch the master color space, you are forced to continue editing on a Proof Copy and that makes total sense.
Quote
Or are you indicating the differences between "Make this the Proof" over "Proof Copy"?
Same thing!
Quote
See how frickin' confusing and frustrating even talking about it is?

I admit I see how confused you are.  ::)
Quote
I'm going back to ACR 6.7 just cool off.
Good idea. When you're ready to understand the architecture in LR in terms of editing upon a soft proof in a workflow, we're here to attempt to assist you.
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AlterEgo

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Re: Lightroom Colour Space
« Reply #15 on: February 25, 2015, 11:29:03 am »

When I open a RAW in LR what space am I rendering in (Melissa/Prophoto?)

the sequence of color transforms is described here = http://wwwimages.adobe.com/content/dam/Adobe/en/products/photoshop/pdfs/dng_spec_1.4.0.0.pdf
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Simon Garrett

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Re: Lightroom Colour Space
« Reply #16 on: February 25, 2015, 11:55:56 am »


When I open a RAW in LR what space am I rendering in (Melissa/Prophoto?)
When I export (say to sRGB) does the colour space conversion take place then (clipping and all)?

the sequence of color transforms is described here = http://wwwimages.adobe.com/content/dam/Adobe/en/products/photoshop/pdfs/dng_spec_1.4.0.0.pdf

A longer list of colour spaces used by Lightroom:
  • The image is always stored in its original colour space
  • Lightroom Develop module uses ProPhoto RGB with a linear Tone Response Curve as its working space for processing, and uses ProPhoto RGB with sRGB's TRC for histogram and pixel values shown under the histogram.  ProPhoto RGB with sRGB TRC is what is referred to as "Melissa RGB".
  • Library module uses previews that are Adobe RGB.
  • As I recall, Web module uses sRGB to preview the web site, but I might have remembered that wrongly.
  • When you export or use Edit In... it uses whatever colour space you specify.  Any clipping resulting from the rendering intent is done then (but you can use Soft Proofing in Develop module to get a preview).

The colour spaces used internally are fixed - you can't alter the working space as you can in Photoshop, for example.
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kirkt

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Re: Lightroom Colour Space
« Reply #17 on: February 25, 2015, 11:59:49 am »

Warning: this post is of interest only to image processing nerds.

When I write image processing code, my go-to representation for RGB color planes is double precision floating point, with the nominal black point 0,0,0 and the nominal white point 1,1,1. However, where it makes sense, and most of the time it does, I allow values below 0 and those above 1. This is especially useful in intermediate calculations. I suspect that Lr does something similar, although I'd expect them to use single precision (32-bit) floating point. Eric Chan, if you see this, could you set me straight?

If that's true, then the gamut of the Lr native color space is not limited to the gamut of PPRGB, since negative values would allow the gamut to be extended without limit to include even more nonphysical triplets and some that actually correspond to visible colors.

Jim


I suspect that this is similar to the approach taken in the beta versions of the upcoming release of Iridient Developer, where the internal working color space is based on ACES (ACES + sRGB tone curve) but processing controls and feedback (curves, histogram, etc.) can be viewed in any user-selected color space via an accompanying dropdown menu, making control and feedback for the user more clearly defined.

From the ID webpage for the beta:

http://www.iridientdigital.com/products/rawdeveloper_history.html

Quote
The "Working Profile" popup menu has been moved to the Curves tab panel and relabeled "RGB Curves Color Space" as this option is now only applicable to the RGB curves adjustments.

Quote
I have switched the RGB Curves Color Spaces for all camera defaults to the Iridient Internal RGB spaces (base on ACES plus sRGB tone curve). I was using an inconsistent mix of sRGB, AdobeRGB, MelissaRGB and ProPhoto in the past depending on camera model. Without any RGB curve edits this change has no impact, but this should help make many user's experience with editing RGB curves more consistent going forward

and

Quote
I have now fully transitioned to a new super wide gamut (color range) internal RGB color space for some operations which is based on the ACES (Academy Color Encoding System) color primaries. This is a bit wider and more specifically designed for use with data from modern digital sensors in mind. My previous internal RGB space which was based on ProPhoto primaries that are also very wide gamut, but primarily designed many years ago primarily for film based workflows.

kirk
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Jim Kasson

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Re: Lightroom Colour Space
« Reply #18 on: February 25, 2015, 12:53:33 pm »

I suspect that this is similar to the approach taken in the beta versions of the upcoming release of Iridient Developer, where the internal working color space is based on ACES (ACES + sRGB tone curve) but processing controls and feedback (curves, histogram, etc.) can be viewed in any user-selected color space via an accompanying dropdown menu, making control and feedback for the user more clearly defined.

From the ID webpage for the beta:

http://www.iridientdigital.com/products/rawdeveloper_history.html


Keep it up, Brian!

Jim

Tim Lookingbill

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Re: Lightroom Colour Space
« Reply #19 on: February 25, 2015, 01:13:35 pm »

It doesn't visually change only because you insist on setting up ProPHoto RGB as a soft proof and the data you see is basically in ProPhoto RGB! If you select another color space, the preview will very likely change because you are far farther from the original and editing that data must and should be done on a VC, NOT THE MASTER!

The data and histogram I see without Soft Proof on is reflecting output of what? Linear with all the Adobe LR default tones applied which would explain why the histogram isn't slammed to the left on a new Raw master in Develop module? Is that correct?

The thing about LR is that images and their edits are in a constant state of perpetuity until the edits are committed to export to a tiff or jpeg so while in LR with Soft Proof turned off the data reflected in the histogram and "%" numbers have very little connection to what's reflected in the preview with regard to measuring and defining the preview through HSL or RGB analysis. Do I have that correct?

I never tried changing Soft Proof setting from ProPhotoRGB to another matrix profile to test to see a preview change, but if I understand you right (despite my doubts I'm able to), if I decide to Soft Proof to a printer profile with edits made using Soft Proof set to ProPhotoRGB on the "Make This The Proof" (I assume this means the master IS the proof) selection, the printer Soft Proof will only reflect the edits applied/encoded on the original master when Soft Proof was off and reflecting Linear with Adobe Default settings applied. Is that right?

I've never printed out of LR, yet, but I can't Soft Proof my printer anyway due to the fact I use Printer Manages Color for my little Epson All In One. So to make this less complicated and more manageable, I'm assuming I shouldn't even turn Soft Proof on to reflect ProPhotoRGB output working on the master and not a VC-(I really don't like making VC's because it creates duplicate thumbnails in Library Grid mode as mentioned above).

I'm having trouble remembering and sorting out in Library Grid mode which are the master and VC or Proof Copy even though I know the icon for VC is the turned page corner in the lower left of the thumbnail. I don't know if that's a Proof Copy VC or just a plain VC and if there is a difference. It turns into a rats nest of duplicate thumbnail previews where you have to look very carefully at those tiny icons.

I'm trying to make LR work like ACR with regard to workflow and thumbnail managing in Library mode and this Soft Proofing thingy on a master or VC or Proof Copy is just too much to rap my head around and keep organized in my head. I'm never going to print out of LR or need Soft Proofing to a printer anyway.

I should keep Soft Proof off if I'm working on the master file if I want to make LR work like ACR.



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