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Author Topic: Colour management work flow have I got this right?  (Read 9763 times)
Andy Yuill
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« on: December 11, 2008, 05:36:28 AM »
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Hello, been trying to learn and resolve some problems that I've been having with colour spaces used in my workflow.  I think that I've got the answer, but I want to run it past the people here to see if I've got it right.

Starting with the problem, well actually lets start with the set up.

I shoot in RAW, camera (40D) set to embed RGB as the profile.
I import into Lightroom 2.1 and do some basic tweaks.
I import into CS4 and process the image further.
I save the image back into Lightroom as a TIFF.
I export the image as a Jpeg for web, printing, and RM stock.

So the what was the problem?

When I viewed the images processed in CS4 and saved as a TIFF  the colours were way out in Lightroom, especially skin tones which were overly pinky/yellow.   But when I then exported those as JPEG using lightroom the colours were a closer match to what I was seeing on CS4.

What I think I was doing wrong was as follows:

RAW (RGB - OK) -> Lighroom (ProPhoto RGB -OK) -> CS4 (AdobeRGB - BAD!) -> Lightroom (ProPhoto RGB - displayed AdobeRGB tagged TIFFs funny) - JPEG (sRGB - which threw away the colours anyway so looked OK)

I've changed the colour space for CS4 to ProPhotoRGB and now the TIFFs are a much closer match from what I see in CS4 to what I see in Lightroom.

But this leaves me with a couple of questions,

What happens at the end of the process when I dump them down into sRGB colour space, how do I control the colours to make sure that they will look ok converting from ProPhoto RGB to sRGB or is this not an issue?

Should I be going through all my old TIFFs and updating their embedded colour space to match the ProPhoto RGB used in lightroom, which is my main library app?


Any comments or advice on what is the best practice would be good.  I'm new to this but doing my best to learn as I go.

Thanks

Andy


www.andyyuill.com
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Mark D Segal
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« Reply #1 on: December 11, 2008, 07:13:44 AM »
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My understanding of the fundamentals underlying these questions is as follows. Corrections from others welcome. When you change the colour space profile embedded in the image you are changing the gamut of colours the image file can reproduce. When an image starts life in Lightroom (where it is displayed in a default workspace akin to ProPhoto) and you export it with a ProPhoto profile, then you re-save it in Photoshop with an sRGB profile or look at it in Photoshop using an sRGB colour working space, because the sRGB colour space is much smaller than the ProPhoto space, you are chopping out many hues and degrees of saturation that may have existed in the ProPhoto version of the file as originally displayed in Lightroom. When they're gone, they're gone if you have saved the file having converted the file's colour space profile from ProPhoto to sRGB. Once a file has been saved and converted with an embedded sRGB profile, if you then expand the colour space by conversion to ProPhoto, you are stretching a smaller colour gamut to fill a larger colour gamut and this can cause colours to change appearance.

As a general rule, to minimize the risk of these unintended colour changes and to take maximum advantage of the colour information in your raw files, keep the ProPhoto profile straight through to printing and make sure your Photoshop working colour space is also ProPhoto. Then if you wish to use these files for email and web display, save a copy of the file and convert the newly saved copy to sRGB with Black Point Compensation. This will help assure the most consistent colour rendition and file usability for internet purposes.
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Mark D Segal (formerly MarkDS)
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Andy Yuill
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« Reply #2 on: December 12, 2008, 03:51:24 AM »
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Thanks mark, so based on that, the issue could be that lightroom was taking an AdobeRGB TIFF and stretching the gamut out so that it was using the full ProPhotoRGB like colour space, and that was what was giving me the colour change from CS4 to Lightroom.

Then when I exported the image as sRGB there was no stretching of the colour space, so the image displayed the same (or at least very close) to the AdobeRGB used in CS4.

Now that my workflow uses ProPhotoRGB all the way till I have to drop it to sRGB for web or print (specified by the lab I use) then I shouldn't get this stretching or smearing from a smaller gamut colour space to a larger gamut colour space.

Ta

Andy


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teddillard
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« Reply #3 on: December 12, 2008, 05:31:32 AM »
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Quote from: Andy Yuill
Thanks mark, so based on that, the issue could be that lightroom was taking an AdobeRGB TIFF and stretching the gamut out so that it was using the full ProPhotoRGB like colour space, and that was what was giving me the colour change from CS4 to Lightroom.

Then when I exported the image as sRGB there was no stretching of the colour space, so the image displayed the same (or at least very close) to the AdobeRGB used in CS4.

Now that my workflow uses ProPhotoRGB all the way till I have to drop it to sRGB for web or print (specified by the lab I use) then I shouldn't get this stretching or smearing from a smaller gamut colour space to a larger gamut colour space.

Ta

Andy

That's a great explanation of that, Mark, and summation Andy...  that's pretty much exactly what is going on.  I always use a pizza dough/cookie cutter analogy- when you're starting with a small color space and remapping to a larger one, think pizza dough- you're spreading the dough out to meet the space.  When you're moving to a smaller space you're using a cookie cutter, (or with perceptual intent, smooshnig the dough together a little before using the cookie cutter).  You can actually watch this going on using the ColorThink software I mentioned in another post.

My personal preference would be to map to AdobeRGB and stay in AdobeRGB until you map down to sRGB or CMYK, but that's a religious debate...  I've pretty much decided to avoid ProPhoto altogether because of the hugeness, and your ability to push outside of any real-life gamut (monitors and printers) before you know it.  Sometime try this- set up your Proof setup and Gamut Warning to, say, your sRGB.  Watch how fast you're out of gamut, working from ProPhoto. As Joe Holmes put it to me, it's about efficiency and a disciplined workflow.

(The Gamut Warning trick is a good way to address the other question you had about how to adjust the colors down from ProPhoto to sRGB, by the way.  You can set that up, and use Hue/Saturation, or your tool of choice, to move the specific colors around until they're within gamut and the warning goes off.)

The one very minor point I'd correct is how you said "chopping out colors displayed in ProPhoto...".  Since most monitors are shooting sRGB, or some equivalent, and even AdobeRGB is well within ProPhoto, the difference between how they're displayed isn't directly because of any chopping of colors you can see.  It's more about remapping colors that are in ProPhoto that you can't see, and how they move around the colors that you see.  Again with the dough- when you shmoosh it into a smaller space you're moving everything around a bit.

Now, as a non-Lightroom user, I have question, Mark.  Are you saying Lightroom only works in, effectively, a ProPhoto space, regardless of the color preferences you have set?
« Last Edit: December 12, 2008, 05:53:35 AM by teddillard » Logged

Ted Dillard
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« Reply #4 on: December 12, 2008, 06:56:04 AM »
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Quote from: teddillard
Are you saying Lightroom only works in, effectively, a ProPhoto space, regardless of the color preferences you have set?


Yes, Lightroom uses a flavor of ProPhoto (Melissa RGB) as it's editing space, even non raw images. As I understand it, this space has all the characteristics (RGB coordinates) of ProPhoto but has a gamma of 1.0 and uses an sRGB Tonal Response curve. The histogram also reflects this linear gamma and sRGB TRC. Only on export from a raw image to a pixel image do you choose a color space.

Dave
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« Reply #5 on: December 12, 2008, 07:06:43 AM »
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Quote from: David Good
Yes, Lightroom uses a flavor of ProPhoto (Melissa RGB) as it's editing space, even non raw images. As I understand it, this space has all the characteristics (RGB coordinates) of ProPhoto but has a gamma of 1.0 and uses an sRGB Tonal Response curve. The histogram also reflects this linear gamma and sRGB TRC. Only on export from a raw image to a pixel image do you choose a color space.

Dave

wow, OK... that's certainly news to me.  There's no way to preview the image in another working space?  Is there a discussion here about why they do it that way?
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Ted Dillard
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« Reply #6 on: December 12, 2008, 07:12:07 AM »
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Quote from: teddillard
That's a great explanation of that, Mark, and summation Andy...  that's pretty much exactly what is going on.  I always use a pizza dough/cookie cutter analogy- when you're starting with a small color space and remapping to a larger one, think pizza dough- you're spreading the dough out to meet the space.  When you're moving to a smaller space you're using a cookie cutter, (or with perceptual intent, smooshnig the dough together a little before using the cookie cutter).  You can actually watch this going on using the ColorThink software I mentioned in another post.

My personal preference would be to map to AdobeRGB and stay in AdobeRGB until you map down to sRGB or CMYK, but that's a religious debate...  I've pretty much decided to avoid ProPhoto altogether because of the hugeness, and your ability to push outside of any real-life gamut (monitors and printers) before you know it.  Sometime try this- set up your Proof setup and Gamut Warning to, say, your sRGB.  Watch how fast you're out of gamut, working from ProPhoto. As Joe Holmes put it to me, it's about efficiency and a disciplined workflow.

(The Gamut Warning trick is a good way to address the other question you had about how to adjust the colors down from ProPhoto to sRGB, by the way.  You can set that up, and use Hue/Saturation, or your tool of choice, to move the specific colors around until they're within gamut and the warning goes off.)

The one very minor point I'd correct is how you said "chopping out colors displayed in ProPhoto...".  Since most monitors are shooting sRGB, or some equivalent, and even AdobeRGB is well within ProPhoto, the difference between how they're displayed isn't directly because of any chopping of colors you can see.  It's more about remapping colors that are in ProPhoto that you can't see, and how they move around the colors that you see.  Again with the dough- when you shmoosh it into a smaller space you're moving everything around a bit.

Now, as a non-Lightroom user, I have question, Mark.  Are you saying Lightroom only works in, effectively, a ProPhoto space, regardless of the color preferences you have set?

Thanks Ted. One rejoinder - the debate about whether to edit in ProPhoto or Adobe RGB98 is not really a religious one - it depends on the facts about how the image is being outputted. While you are right that most of our displays don't see much beyond sRGB, our new generation of professional printers sport gamuts for which some hues do extend beyond AdobeRGB98, hence for such files it would be nice to preserve the data and capture it in print. In fact, using Ilford Gold Fibre Silk in my Epson 3800, sometimes I get prints holding colours that are actually richer than what I see on my well-calibrated and well-profiled LaCie 321-1 display, so it isn't imaginery, theoretical, or worse yet, religious  

Yes, correct - we're talking about re-mapping - that's the method by which one ends-up chopping something somehow moving from a wider to a narrower gamut.

As far as I know and can see, there is no choice of colour working space in Lightroom. The program works according to the colour space profile embedded in the image. The choice begins upon exporting the image to a pixel-editing application.
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Mark D Segal (formerly MarkDS)
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« Reply #7 on: December 12, 2008, 08:16:40 AM »
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Quote from: MarkDS
Thanks Ted. One rejoinder - the debate about whether to edit in ProPhoto or Adobe RGB98 is not really a religious one - it depends on the facts about how the image is being outputted. While you are right that most of our displays don't see much beyond sRGB, our new generation of professional printers sport gamuts for which some hues do extend beyond AdobeRGB98, hence for such files it would be nice to preserve the data and capture it in print. In fact, using Ilford Gold Fibre Silk in my Epson 3800, sometimes I get prints holding colours that are actually richer than what I see on my well-calibrated and well-profiled LaCie 321-1 display, so it isn't imaginery, theoretical, or worse yet, religious  

Yes, correct - we're talking about re-mapping - that's the method by which one ends-up chopping something somehow moving from a wider to a narrower gamut.

As far as I know and can see, there is no choice of colour working space in Lightroom. The program works according to the colour space profile embedded in the image. The choice begins upon exporting the image to a pixel-editing application.

Well, again that's news to me.  Ever the skeptic, (especially in religious matters) I downloaded the profile for the Ilford Gold Fibre Silk and ran some very quick comparisons using the Apple ColorSync Utility.  (Applications>Utilities>ColorSync Utility)  Here's what I saw.  

[attachment=10262:Picture_3.png]

First, the paper compared to AdobeRGB, (I've "held for comparison" the Adobe, and you see it as the white shadow, in case some readers are not familiar with this...)  and dammit, you're right.  Especially in the typical problematic colors (my personal gremlin, the cobalt blue), you can see the paper can handle stuff that's outside of Adobe RGB.  

[attachment=10263:Picture_4.png]

When you look at the paper compared to ProPhoto, you still even get a smidge of my cobalt blue poking out.  

DAMN!  

However, I still have big concerns about the other areas of ProPhoto, the relatively massive spaces that are unused, and mostly this is because of Joe's harping on using color profiles that are "efficient"...  justifying his specifically designed camera working spaces...  

Thanks for that Mark!
« Last Edit: December 12, 2008, 08:19:00 AM by teddillard » Logged

Ted Dillard
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« Reply #8 on: December 12, 2008, 08:44:43 AM »
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Ted, good you did that - interesting confirmation.

Now, on what LR is actually doing, Martin Evening has that nailed in his excellent book "The Adobe Photoshop Lightroom 2 Book", pages 570-571. David's description of the character of Lightroom's "ProPhoto" colour space corresponds with how Martin describes it too. Martin further explains, if I am parsing several pages of text correctly, that while Lightroom calculates all the Develop adjustments in its native colour space ("Melissa RGB"), it recognizes and portrays colours according to the embedded colour space of the image file. If the image file has no embedded colour space, it assigns sRGB. Raw files don't have colour profiles, but when the user exports the file to a pixel editing program and selects a colour space for that export, the selected colour space is then embedded in the file. Depending on the image data, clipping can occur when selecting a narrower colour space such as sRGB on export from Lightroom.
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Mark D Segal (formerly MarkDS)
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« Reply #9 on: December 12, 2008, 08:50:25 AM »
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Quote from: David Good
Yes, Lightroom uses a flavor of ProPhoto (Melissa RGB) as it's editing space, even non raw images. As I understand it, this space has all the characteristics (RGB coordinates) of ProPhoto but has a gamma of 1.0 and uses an sRGB Tonal Response curve. The histogram also reflects this linear gamma and sRGB TRC. Only on export from a raw image to a pixel image do you choose a color space.

Dave

To be clear, Melissa RGB is only used for the Histogram and RGB percentages you see. Its using ProPhoto RGB primaries with a TRC ("gamma") of 2.2. Its not used for any processing or encoding.

The underlying color space Lightroom and ACR use has no name, but its ProPhoto primaries using a TRC 1.0 gamma.

In terms of gamut and printers, Mark has gone over this and discusses the 3800. Note that the new K3 HDR inks are even larger!

Also, there's the gamut of the scene, the gamut of the capture device (kind of, digital cameras don't really have a gamut) and gamut of the encoding space. The same 5D shooting a gray card and a vibrant scene of fall foliage will produce of course, quite different gamut possibilities that we could encode into a working space. But there are lots of real world scenes we can capture and then print that exceed the gamut boundaries that Adobe RGB (1998) allows. That gray card isn't stretched to the boundaries of ProPhoto RGB of course. But the container allows us to avoid clipping colors that we might be able to capture, and output that would clip if the boundaries of an encoding color space were as "small" as Adobe RGB (1998), let alone sRGB.
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« Reply #10 on: December 12, 2008, 09:21:19 AM »
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Quote from: MarkDS
Ted, good you did that - interesting confirmation.

Now, on what LR is actually doing, Martin Evening has that nailed in his excellent book "The Adobe Photoshop Lightroom 2 Book", pages 570-571. David's description of the character of Lightroom's "ProPhoto" colour space corresponds with how Martin describes it too. Martin further explains, if I am parsing several pages of text correctly, that while Lightroom calculates all the Develop adjustments in its native colour space ("Melissa RGB"), it recognizes and portrays colours according to the embedded colour space of the image file. If the image file has no embedded colour space, it assigns sRGB. Raw files don't have colour profiles, but when the user exports the file to a pixel editing program and selects a colour space for that export, the selected colour space is then embedded in the file. Depending on the image data, clipping can occur when selecting a narrower colour space such as sRGB on export from Lightroom.

cool... loving my second and third looks at Lightroom2, I guess I'm going to have to read up, thanks for the book ref.  (I haven't found a great way to work with LR yet with my happy Smart Objects.)

and like I said elsewhere, I'm into the visuals.  
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« Reply #11 on: December 12, 2008, 09:59:36 AM »
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Quote from: digitaldog
To be clear, Melissa RGB is only used for the Histogram and RGB percentages you see. Its using ProPhoto RGB primaries with a TRC ("gamma") of 2.2. Its not used for any processing or encoding.

The underlying color space Lightroom and ACR use has no name, but its ProPhoto primaries using a TRC 1.0 gamma.

Thank-you for clarifying that Andrew. I guess it could be equated to a printer profile with it's soft-proofing and output tables, only this time the soft-proof (Melissa) is "gamma" 2.2 and the output (no name) is "gamma" 1.0 .
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« Reply #12 on: December 12, 2008, 10:39:42 AM »
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Quote from: David Good
Thank-you for clarifying that Andrew. I guess it could be equated to a printer profile with it's soft-proofing and output tables, only this time the soft-proof (Melissa) is "gamma" 2.2 and the output (no name) is "gamma" 1.0 .

Close. You can't output the no name, gamma 1.0 space in ACR. In theory you could in LR 2.0 for whatever reason, by first building a custom working space in Photoshop and then using the Export option in LR and selecting it. But why? You'd probably be going ProPhoto RGB to this hybrid space, might as well encode in ProPhoto.
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« Reply #13 on: December 12, 2008, 11:47:42 AM »
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Quote from: digitaldog
Also, there's the gamut of the scene, the gamut of the capture device (kind of, digital cameras don't really have a gamut) and gamut of the encoding space. The same 5D shooting a gray card and a vibrant scene of fall foliage will produce of course, quite different gamut possibilities that we could encode into a working space. But there are lots of real world scenes we can capture and then print that exceed the gamut boundaries that Adobe RGB (1998) allows. That gray card isn't stretched to the boundaries of ProPhoto RGB of course. But the container allows us to avoid clipping colors that we might be able to capture, and output that would clip if the boundaries of an encoding color space were as "small" as Adobe RGB (1998), let alone sRGB.

This brings up a really interesting point, and one that comes up every class I teach...  the question of, "well, if I can't reproduce the colors I see, then what does it all matter?"  Most often I hear it when talking about working in ProPhoto or Adobe and then printing to an inkjet printer, but, as you've noted Andrew, it goes right on back to the subject, and carries through each reductive step along the way.  

My answer is that this is no different than any other medium, and the goal of the artist is to learn the tools so that the final work represents the vision of the artist, not the actual reality of the subject.  Precisely because of the limitations of the medium, we are awe-struck by the elegance of Picasso's line, Adam's prints...  By understanding and controlling the medium (the negative, exposure, development and printing, in Adams' case, the limited palette of black and white prints convey the vision he has as an artist.  Matisse, through mastery of the brush, conveys the elegance of the line of a woman's neck with one precise stroke.  

I think we sometimes lose sight of that, for all the precision and accuracy of the digital process.  For all the tools, including color management, HDR, the gamut of printers like the 3800 and the Ilford paper, we still are, at base, trying to convey the feeling we had, the vision we saw, when we made the exposure with a severely limited set of tools.  To bring this back down to earth, understanding how to manage the color from exposure through to the final print is essential in this process... the entire range Andrew describes.  For example, making sure you're working in an ever-decreasing spiral, rather than the process that started this post, sort of a cut, stretch and cut sequence, helps you manage those relationships (whether that spiral starts with ProPhoto or Adobe1998.  

crap.  where the hell did THAT all come from?  I gotta check my meds, brb.

 
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« Reply #14 on: December 12, 2008, 12:06:41 PM »
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Quote from: digitaldog
Close. You can't output the no name, gamma 1.0 space in ACR. In theory you could in LR 2.0 for whatever reason, by first building a custom working space in Photoshop and then using the Export option in LR and selecting it. But why? You'd probably be going ProPhoto RGB to this hybrid space, might as well encode in ProPhoto.

Exactly, I have used PP for years, just trying to make a comparison for those that may familiar with printer profiles (2 "sides"). I just noticed through a google search that you have a lengthy presentation pdf on this very subject entitled "CMS in LR CR" partway down on this page:      http://digitaldog.net/files/ .  Thanks for sharing, I'll read up and refresh on it.

Dave
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« Reply #15 on: December 12, 2008, 01:52:08 PM »
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In brief, a good tone mapping or gamut mapping algorithm could make use of the printer's "extra colors" to help preserve color appearance as you move from display to print, even if those extra colors aren't reproducible on your display. That is why they are useful to have and to preserve.
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« Reply #16 on: December 12, 2008, 01:55:15 PM »
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Quote from: David Good
As I understand it, this space has all the characteristics (RGB coordinates) of ProPhoto but has a gamma of 1.0 and uses an sRGB Tonal Response curve.

No. Melissa RGB uses an sRGB curve. Full stop. That curve is the "gamma", in so much as you can talk about gamma in context of an sRGB tone curve - technically gamma only really applies when the curve is a pure exponential. The sRGB curve is mostly exponential, roughly 2.2 for most of its range, but with a linear portion at the base. It's certainly no where near a gamma of 1 however.

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« Reply #17 on: December 12, 2008, 04:01:15 PM »
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Quote from: teddillard
cool... loving my second and third looks at Lightroom2, I guess I'm going to have to read up, thanks for the book ref.  (I haven't found a great way to work with LR yet with my happy Smart Objects.)

and like I said elsewhere, I'm into the visuals.  

Well, if you are into visuals, I'd also highly recommend this, by Michael Reichmann and Jeff Schewe, which you can buy right here: http://store.luminous-landscape.com/zencar...products_id=203. It's excellent.
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Mark D Segal (formerly MarkDS)
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« Reply #18 on: December 12, 2008, 04:07:25 PM »
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Quote from: sandymc
No. Melissa RGB uses an sRGB curve. Full stop. That curve is the "gamma", in so much as you can talk about gamma in context of an sRGB tone curve - technically gamma only really applies when the curve is a pure exponential. The sRGB curve is mostly exponential, roughly 2.2 for most of its range, but with a linear portion at the base. It's certainly no where near a gamma of 1 however.

Sandy

From Martin Evening, page 570: "........the space is using ProPhoto chromaticities, but with a gamma of 1.0.........Meanwhile the Lightroom viewing space uses the same ProPhoto RGB chromaticities but with an sRGB tone response curve." He goes on to explain that the gamma of 1.0 was chosen because raw files have a gamma of 1.0 allowing Lightroom to process the files in their native gamma.
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Mark D Segal (formerly MarkDS)
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« Reply #19 on: December 12, 2008, 11:12:49 PM »
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Quote from: MarkDS
From Martin Evening, page 570: "........the space is using ProPhoto chromaticities, but with a gamma of 1.0.........Meanwhile the Lightroom viewing space uses the same ProPhoto RGB chromaticities but with an sRGB tone response curve." He goes on to explain that the gamma of 1.0 was chosen because raw files have a gamma of 1.0 allowing Lightroom to process the files in their native gamma.

The key word is the "but", as in "but with an sRGB tone response curve". Internally, of course LR works in a linear color space, as does every raw converter. But all of its readouts, histograms, etc are in a sRGB space, not linear. It's easy to prove this; just take a calibration image with known values, and take a look at what the RGB readouts are - they will be in an sRGB space.

Sandy
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