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Author Topic: Does a raw file have a color space?  (Read 190453 times)

Iliah

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Does a raw file have a color space?
« Reply #140 on: January 26, 2008, 12:35:31 pm »

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You have contributed nothing significant to this thread and it is a waste of time to debate with you for the reasons given above.

Dear Bill, I can't agree with you at all. Jeff contributed his photographic vision of the matter. For a photographer it is quite obvious that today the whole colour space concept does not work for raw data. It is just plain visible.
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Panopeeper

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Does a raw file have a color space?
« Reply #141 on: January 26, 2008, 01:15:15 pm »

Lastly back (?) to a discussion based on reasoning instead of emotions and face-saving activities.

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1. The color data in the RAW is not as strictly defined. The spectral characteristics of the camera CFA are not included in the RAW data

The color data of the raw image is strictly defined by the spectral characteristics of the sensor and filters.

IMO it is irrelevant if the characteristics included in the file or not.

a. Let's assume, that we add an array per filter color to the raw file, describing the spectral responses in 1 nm steps, which is more than enough. Would the color information suddenly become a color space?

b. Billions of sRGB JPEG images do not carry any color space information in the file. Are their colors in a color space or not?

c. Is it enough to know, which color space applies to a given image, or is  it necessaruy to include the color space's description in each file? A raw image file carries the identification of the camera, which implies the characteristics.

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even if they were, choosing the best way to handle the mismatches between the CFA response and that of the human eye boils down to a judgment call, and no one method is always superior. The best we can do so far is to make an approximation that works in as many situations as possible, but there is no perfect method yet

In other words your definition includes the requirement, that there be the knowledge in public domain, how to do the best transformation. Fair enough.

Btw, the claim that no one method is always superior is unsupported.

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The RAW data must have a white balance assigned to it before any color conversion to LAB or a standard RGB editing space can occur. This is another judgment factor, and varying this can change the accuracy of the color conversion dramatically

What about an in-camera TIFF or JPEG with incorrect WB setting? What about the image after raw conversion with a WB setting, which has to be changed later? Do such images become "color space-less" suddenly?

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Not only the nature of raw data is very different from what "colorimetric colour space" describes

The existence of the two distinct terms color space and colorimetric color space implies, that these are not the same.

No-one claimed, that (all) raw images are colorimetric.

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Operations over the raw data that leave it in raw state is an oxymoron

Raw state is not a color space. However, for example Canon 1DsMkIII raw image implies a color space (IMO). Many operations on the raw image leave that unchanged, for example white balancing, lightness adjustment, black point and white point setting.

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Sensor changes its response substantially across its surface, and depending on the heat which is also non-uniform across the sensor and other elements in the pipeline. Some cameras include autocalibration to account for that, even changing white balance coefficients that go into metadata; some don't

This is supposed to be an argument for or against what?

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in some we apply both white balance and gamma transform - and then go to demosaicing

Again, this is irrelevant, but I doubt it anyway ("gamma transform" before de-mosaicing). Though there is no limit of making something worse and worse.
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Gabor

Jonathan Wienke

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Does a raw file have a color space?
« Reply #142 on: January 26, 2008, 01:18:11 pm »

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One more minor point - I do not see why you brought ProPhoto to this. However I leave it to you.

I was just using ProPhoto as an example of a fully-defined, unambiguous RGB color space. That is all.
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bjanes

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Does a raw file have a color space?
« Reply #143 on: January 26, 2008, 01:40:43 pm »

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Dear Bill, I can't agree with you at all. Jeff contributed his photographic vision of the matter. For a photographer it is quite obvious that today the whole colour space concept does not work for raw data. It is just plain visible.
[a href=\"index.php?act=findpost&pid=169758\"][{POST_SNAPBACK}][/a]

Iliah,

Thanks for your comments. I guess I'm more into the science of the discussion and "the vision thing" escapes me.

I should point out to our readers that you are the author of Raw Magick, a well regarded but little used raw converter for Nikon raw files. Adobe Camera Raw does appear to use a 3x3 matrix transform to transform the "camera space" into a colorimetric working space and you criticized this approach in the DPReview thread: "That makes the methods used by Adobe look sub-optimal and some folks feel bad about that defending their beloved." Since Jeff is an ACR proponent and his mentor is Thomas Knoll, it seems strange that he would object to the non-colorimetric color space 3x3 transform approach that Adobe uses. Has he actually objected?

Could you explain briefly how Raw Magick and possibly Nikon Capture differ in interpreting non-colorimetric data and how the results differ subjectively and in terms of delta E?

Finally, I have received a number of private e-mails congratulating me for standing up to the "bullies". These persons do not wish to go public and be subject to the abuse that would ensue. Perhaps I misinterpreted the intent of your Proverbs quotation. How is it to be interpreted?

Regards,

Bill
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Jonathan Wienke

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Does a raw file have a color space?
« Reply #144 on: January 26, 2008, 01:56:57 pm »

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Lastly back (?) to a discussion based on reasoning instead of emotions and face-saving activities.
The color data of the raw image is strictly defined by the spectral characteristics of the sensor and filters.


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a. Let's assume, that we add an array per filter color to the raw file, describing the spectral responses in 1 nm steps, which is more than enough. Would the color information suddenly become a color space?

You're forgetting one extremely important factor, the color characteristics of the lighting of the subject. It is not enough to know exactly the color behavior of the camera sensor and CFA. In order to process the RAW properly, we must define white balance somehow. This is the fundamental ambiguity I'm talking about. Regardless of how well documented the camera/sensor behavior, there are a large number of materially different unique RAW files that can correspond with a given subject, depending on the spectral distribution of the lighting.

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IMO it is irrelevant if the characteristics included in the file or not.

b. Billions of sRGB JPEG images do not carry any color space information in the file. Are their colors in a color space or not?

c. Is it enough to know, which color space applies to a given image, or is  it necessaruy to include the color space's description in each file? A raw image file carries the identification of the camera, which implies the characteristics.

In other words your definition includes the requirement, that there be the knowledge in public domain, how to do the best transformation. Fair enough.

Not exactly. I'm proposing the notion that a full-fledged color space has one and only one unambiguous numeric designation for a color that falls within its gamut. If you take the sRGB color R215, G133, B37 you have a particular shade of orange. If you convert that color to LAB or ProPhoto, you have one and only one set of values that represents that color in those spaces. This is not true of RAW data.

Let's  consider a Foveon RAW to eliminate the complications of demosaicing and color interpolation. You can shoot a Color Checker in a variety of lighting conditions and the RAW data values will be materially different, even though the colors of the subject have not changed. With a good selection of white balance values for each conversion, one can make all of them match quite closely after converting to ProPhoto. The proper colorimetric interpretation of the RAW data is dependent on what the meaning of "is" is, AKA the WB setting. This is not true of a properly converted JPEG image, whether or not it has a profile tag. As long as we know what the correct profile is, we can display the image with unambiguously correct colors. But with RAW, we can't tell from the RAW data alone (even with detailed camera spectral response data) the difference between a white object illuminated by an orange light source and an orange object being illuminated by a white light source.

I think ultimately the solution to more accurate color from RAW will be to use a conversion process that accounts for the spectral response of the camera sensor + CFA and the spectral characteristics of the lighting. This would reduce or eliminate changes in the output color palette when shooting with spiky light sources like sodium vapor lamps vs. continuous spectrum sources like sunlight.
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papa v2.0

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Does a raw file have a color space?
« Reply #145 on: January 26, 2008, 02:01:53 pm »

I think if you all look at the following chapters in

Colour Engineering, Achieving Device Independent Colour, (2002) Eds Phil Green and Lindsay Macdonald. John Wiley & Sons Ltd, England.
ISBN 0-471-48688-4.

For PANOPEEPER

"The color data of the raw image is strictly defined by the spectral characteristics of the sensor and filters.

IMO it is irrelevant if the characteristics included in the file or not. "


Chapter  6
Overview of characterization Methods - Phil Green.

Give a good outline of device characterization and the relationship with CIE colorimetry.


And for the rest of the contributers to this thread I hope this will eventually clear thins up.

Chapter 8
Methods for characterizing colour scanners and digital cameras -Tony Johnston.

Chapter 9
Colour processing for digital photography - Jack Holm, Ingeborg Tastl, Larry Hanlon and Paul Hubel.

Chapter 17
 Managing color in digital image libraries- Sabine Süsstrunk



There is enough content to settle this debate - just read and enjoy!
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Iliah

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Does a raw file have a color space?
« Reply #146 on: January 26, 2008, 02:05:17 pm »

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Adobe Camera Raw does appear to use a 3x3 matrix transform to transform the "camera space" into a colorimetric working space
Dear Bill, I would call the above an oversimplification.
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you criticized this approach in the DPReview thread: "That makes the methods used by Adobe look sub-optimal and some folks feel bad about that defending their beloved."
This was targeted at you, Bill. Sorry. You are defending in this thread things that you do not understand. Watching you in this thread I thought first we have a case of stolen identity. I never saw you before insulting people that way.
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Since Jeff is an ACR proponent
Maybe not when it comes to blindly accepting default colour from ACR/LR. You should remember this response from Jeff, as you participated in that thread:
"The way I do it is open the image in DPP running iin the background and open the image in Camera Raw in the foreground and then adjust the Camera Raw renderings to match (more or less) the DPP renderings. Yes it involves adjusting the Calibrate sliders after careful WB and tone settings that may include curves...if you find a setting you like or matches the DPP rendering, save it out as a saved setting or subsetting. "
https://forum.adobe.com/webx/.3bbd164e.3bbf2d76?14
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I should point out to our readers that you are the author of Raw Magick, a well regarded but little used raw converter for Nikon raw files."
Do you have the number of users to claim it is "little used"?
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Jonathan Wienke

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Does a raw file have a color space?
« Reply #147 on: January 26, 2008, 02:06:59 pm »

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"The color data of the raw image is strictly defined by the spectral characteristics of the sensor and filters.

No it isn't. Your statement is equivalent to saying that exposure is defined by shutter speed irrespective of aperture and ISO. The camera sensor/CFA characteristics are only half of the equation. The spectral characteristics of the lighting are equally pertinent to the RAW values that are recorded, which is why every RAW converter has a White Balance setting. If RAW data was unambiguously colorimetric like LAB or ProPhoto RGB, then a white balance setting would be unnecessary.
« Last Edit: January 26, 2008, 02:17:12 pm by Jonathan Wienke »
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papa v2.0

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Does a raw file have a color space?
« Reply #148 on: January 26, 2008, 02:37:16 pm »

Sorry Johnathan
that was supposed to be a quote from Panopeeper

My mistook. ill use the qoute button next time.
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bjanes

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Does a raw file have a color space?
« Reply #149 on: January 26, 2008, 02:39:02 pm »

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I think if you all look at the following chapters in

Colour Engineering, Achieving Device Independent Colour, (2002) Eds Phil Green and Lindsay Macdonald. John Wiley & Sons Ltd, England.
ISBN 0-471-48688-4.



Chapter 9
Colour processing for digital photography - Jack Holm, Ingeborg Tastl, Larry Hanlon and Paul Hubel.

Chapter 17
 Managing color in digital image libraries- Sabine Süsstrunk
There is enough content to settle this debate - just read and enjoy!
[{POST_SNAPBACK}][/a]

Papa,

I'm sure your references would be helpful in understanding the issues, but how many people do you think are going to buy these references? The Green et al book appears pretty technical and may be more than most of us need.

[a href=\"http://www.amazon.com/s/ref=nb_ss_gw/103-2409157-8372632?url=search-alias%3Daps&field-keywords=Colour+Engineering&x=17&y=15]Color Engineering [/url]: US $132 at Amazon.com

Some online references would be more helpful.

Bill
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bjanes

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Does a raw file have a color space?
« Reply #150 on: January 26, 2008, 02:57:28 pm »

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Maybe not when it comes to blindly accepting default colour from ACR/LR. You should remember this response from Jeff, as you participated in that thread:

"The way I do it is open the image in DPP running iin the background and open the image in Camera Raw in the foreground and then adjust the Camera Raw renderings to match (more or less) the DPP renderings. Yes it involves adjusting the Calibrate sliders after careful WB and tone settings that may include curves...if you find a setting you like or matches the DPP rendering, save it out as a saved setting or subsetting. "
https://forum.adobe.com/webx/.3bbd164e.3bbf2d76?14
[a href=\"index.php?act=findpost&pid=169784\"][{POST_SNAPBACK}][/a]

In that thread Jeff was merely telling us how he gets the output ACR to more or less match that of DPP. He did not state which default color was preferable or more accurate and certainly he made no mention of undesirable characteristics in the non-colorimetric rendering by ACR, nor did he mention the conversion methods used by DPP. He mentions the calibrate tab of ACR; as I understand it, the calibrate procedure adjusts the matrix coefficients for the transform and makes use of the ACR approach of matrix conversion rather than negating it.

Of course, this may be an oversimplification and I don't have more than a general concept of the process. Perhaps you can offer some clarification?

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Do you have the number of users to claim it is "little used"?
[a href=\"index.php?act=findpost&pid=169784\"][{POST_SNAPBACK}][/a]

Not at the tip of my fingers. I've seen surveys that list ACR/Lightroom at the top of the list followed by the camera makers programs, Bibble, and a few others. I have not seen Raw Magick on the lists. Perhaps you can give us some figures. I am a registered user of Raw Magick and like it, but personally I use ACR because it does a good job and fits into my work flow. I use Raw Magick and even Nikon Capture NX on selected important images.

That said, I do not consider myself a cheerleader for ACR or its conversion methods, but merely stated that Thomas Knoll considered that raw files have a color space, which differs in certain respects from some more common working spaces.

Regards,

Bill
« Last Edit: January 26, 2008, 04:47:28 pm by bjanes »
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papa v2.0

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Does a raw file have a color space?
« Reply #151 on: January 26, 2008, 03:04:50 pm »

Unfortunately there's not much at that level on the web.

Technical, yes but I think if you really want an understanding of current issues facing digital photography and colour management, I would recommend it.

Its well written and for those  who have been in this thread I dont think it would be beyond them.
It took me several reads to digest it! Burp!

A good site is of course the ICC  

http://www.color.org/index.xalter

and the guy to ask is Phil!
He will put you right!

or here is set of link that might helphttp://www.digitalcolour.org/Links.htm
« Last Edit: January 26, 2008, 03:08:50 pm by papa v2.0 »
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Jonathan Wienke

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Does a raw file have a color space?
« Reply #152 on: January 26, 2008, 03:10:03 pm »

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Sorry Johnathan
that was supposed to be a quote from Panopeeper

Oops. My mistake. Regardless of who made the statement, my objection to it is still the same.
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Panopeeper

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Does a raw file have a color space?
« Reply #153 on: January 26, 2008, 03:26:37 pm »

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The camera sensor/CFA characteristics are only half of the equation

That is unquestionable; I understood my

The color data of the raw image is strictly defined by the spectral characteristics of the sensor and filters

regarding the raw data in general, not a specific image. The specific white balance is a characteristic of the particular image, which has to be assigned independently of the color space in use.

As ACR demonstrates it, the WB can be (re)set even in JPEG form.

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If RAW data was unambiguously colorimetric like LAB or ProPhoto RGB, then a white balance setting would be unnecessary.

Again: no-one claimed the raw images (in general) to be colorimetric (colorimetric implies unambiguousity).

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If you convert that color to LAB or ProPhoto, you have one and only one set of values that represents that color in those spaces

This is a fundamental mistake; please re-evalute this point, which may influence your opinion on the topic.
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Gabor

Panopeeper

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Does a raw file have a color space?
« Reply #154 on: January 26, 2008, 03:32:31 pm »

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Adobe Camera Raw does appear to use a 3x3 matrix transform to transform the "camera space" into a colorimetric working space

ACR uses two transforms for two different illuminations (I have not see anything else but "Standard illuminant A" and D65). The matrices for other illuminations are interpolated based on these two.
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Gabor

Jonathan Wienke

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Does a raw file have a color space?
« Reply #155 on: January 26, 2008, 03:42:24 pm »

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This is a fundamental mistake; please re-evalute this point, which may influence your opinion on the topic.

Please explain what you mean. sRGB 215, 133, 37 has one and only one equivalent color value in ProPhoto (161, 124, 51) or LAB (63, 27, 61). In contrast there are many RAW values that can be converted to this shade of orange, depending on the spectral characteristics of the lighting.
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Panopeeper

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Does a raw file have a color space?
« Reply #156 on: January 26, 2008, 07:28:23 pm »

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sRGB 215, 133, 37 has one and only one equivalent color value in ProPhoto (161, 124, 51) or LAB (63, 27, 61). In contrast there are many RAW values that can be converted to this shade of orange, depending on the spectral characteristics of the lighting

That's right, in this direction. However, your statement was

you have one and only one set of values that represents that color in those spaces

The backward conversion is ambiguous.
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Gabor

Jonathan Wienke

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Does a raw file have a color space?
« Reply #157 on: January 26, 2008, 07:59:33 pm »

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The backward conversion is ambiguous.

Ambiguous how? If you're in 16-bit mode in PS, you can convert back and forth between sRGB, ProPhoto, and LAB numerous times before rounding errors change any of the 8-bit versions of the channel values. It's anything but ambiguous. It's only when you try to convert from sRGB back to RAW that things get ambiguous.
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Panopeeper

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Does a raw file have a color space?
« Reply #158 on: January 26, 2008, 08:43:44 pm »

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If you're in 16-bit mode in PS, you can convert back and forth between sRGB, ProPhoto, and LAB numerous times before rounding errors change any of the 8-bit versions of the channel values. It's anything but ambiguous

Not so. How do you think the projection from a larger set on a smaller one can be unambiguous?

I suggest you to pick an image with strong (saturated) colors, or use this shot of colorful silk flowers: http://www.panopeeper.com/Download/RawDemo_40D_3.CR2

Convert it in ProPhoto with ACR and load it in PS, in 16bit. Check out the gamut (Shift-Ctrl-Y), there must be quite a few places warning of conversion problem.

Make four copies of it and convert them in sRGB with the four different intents.

Copy these as layers together and compare them against each other in difference mode; the differences are tiny, but they are there (you need to magnify the differences, for example by a curve). The saturation against the perceptual shows no difference, but the difference is undisputable against the relative version.

But that's nothing. Make another copy and convert it in sRGB with saturation intent, but this time using the Microsoft engine. Layer that one to the others and be surprized.
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Gabor

digitaldog

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Does a raw file have a color space?
« Reply #159 on: January 26, 2008, 08:46:56 pm »

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Make four copies of it and convert them in sRGB with the four different intents.

Four? That those profiles only have a colorimetric table. Absolute will likely look funky. RelCol is going to be what you get with Saturation or Perceptual selected in Photoshop since those tables don't exist.
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