1 2 Previous Next 65 Replies Latest reply on Jun 1, 2010 2:01 PM by Hudechrome-sd9sPI

    Pet Peeve:  Loss of Data on Conversion to other than ProPhoto RGB

    Noel Carboni Level 7

      Fact:  Camera Raw chooses to clip highlights and shadows for all color spaces other than ProPhoto RGB.

       

      I suppose the thinking must be "ProPhoto is a wider gamut color space, and so therefore must be better at representing the colors the camera has captured in some measurable way".

       

      Bunk.

       

      It's easy to demonstrate that the original camera data contains information that is lost.  Convert an image with a very bright blue color in it to an sRGB image, and convert the same image using the ProPhoto RGB space.  Look at the histograms during and after conversion.

       

      It would be FAR more useful to convert the entire range of colors the camera has captured to fit in the target color space.  Throwing away highlight and shadow data arbitrarily, while at the same time providing "recovery" capabilities, seems just plain silly.  The sliders sometimes help but usually the adjustments have to be so extreme that they ruin the rest of the image.  You can't recover the lost data except to convert to ProPhoto RGB.

       

      I really don't want to hear that the intent is to be "true to the math", that's complete horseradish; there are a hundred other things Camera Raw does to tweak the data to make it more useful or pleasing.  You can't make a valid argument for intentionally clipping the data while at the same time offering a "Recovery" slider.  You simply can't.

       

      For my needs I greatly prefer to work in sRGB space, so what I've done is this:  I convert to ProPhoto RGB, and I've developed an action that "rolls off" the shadows and highlights during a conversion to sRGB so that all the information for both shadows and highlights is retained.  My workflow in Photoshop starts like this:  Convert, then press the F14 key (if I don't forget).  The images LOOK identical, but my sRGB result is FAR better than a direct conversion to sRGB, because I still have all the shadow and highlight data to work with.

       

      How about fixing this so I don't keep having to go through the extra step?

       

      How about fixing this so the people converting directly to sRGB stop losing data their cameras have captured?

       

      Thanks.

       

      -Noel

        • 1. Re: Pet Peeve:  Loss of Data on Conversion to other than ProPhoto RGB
          Noel Carboni Level 7

          I've put a Canon EOS-40D raw image online that can be used to demonstrate black point clipping in the red channel.

           

          http://images.ProDigitalSoftware.com/IMG_1775.CR2

           

          -Noel

          • 2. Re: Pet Peeve:  Loss of Data on Conversion to other than ProPhoto RGB
            Jeff Schewe Level 5

            Noel Carboni wrote:

             

            I really don't want to hear that the intent is to be "true to the math", that's complete horseradish; there are a hundred other things Camera Raw does to tweak the data to make it more useful or pleasing.  You can't make a valid argument for intentionally clipping the data while at the same time offering a "Recovery" slider.  You simply can't.

             

            Well, yes you can. The camera is capturing color outside the color space of sRGB or Adobe RGB. The color can ONLY be contained in ProPhoto RGB. So, when you go from contained in Photo Photo RGB and do a color transform to sRGB you get clipping because there's no other way to deal with out of gamut colors in display based color spaces. Color space transforms from one working space to another (say ProPhoto RGB > sRGB) use Relative Colorimetric rendering intents...there's no support for Perceptual rendering intents (which is what you are asking for) unless you use a V4 color space profile which includes Perceptual-which while out there, they are not yet standard and fully supported.

            • 3. Re: Pet Peeve:  Loss of Data on Conversion to other than ProPhoto RGB
              Noel Carboni Level 7

              Oh, so you're telling me that a new camera model, one that has, say, 2 stops more dynamic range than a current model which just happens to fill the ProPhoto RGB color space from dark to light, will not fit, and Camera Raw will simply clip both ends even when converting to ProPhoto RGB?

               

              I doubt it.


              The mapping of the brightness levels to fit the color space is completely at the choice of the software designer.  You could make the entire dataset fit in any given color space by ranging the numbers properly.

               

              I'm not talking about converting from sRGB to ProPhoto RGB here, I'm talking about the initial assignment of converted data into a color space.

               

              -Noel

              • 4. Re: Pet Peeve:  Loss of Data on Conversion to other than ProPhoto RGB
                Jeff Schewe Level 5

                Noel Carboni wrote:

                 

                I'm not talking about converting from sRGB to ProPhoto RGB here, I'm talking about the initial assignment of converted data into a color space.

                 

                 

                Yes, actually, you are...Camera Raw, when it first opens an image, does a camera color to Pro Photo RGB primaries conversion for the Camera Raw processing pipeline. When you choose a different color space in the Workflow Settings in Camera Raw you are calling up a traditional color space profile conversion...with the same limits as doing a profile conversion inside of Photoshop.

                 

                Noel Carboni wrote:

                 

                Oh, so you're telling me that a new camera model, one that has, say, 2 stops more dynamic range than a current model which just happens to fill the ProPhoto RGB color space from dark to light, will not fit, and Camera Raw will simply clip both ends even when converting to ProPhoto RGB?

                 

                The mapping of the brightness levels to fit the color space is completely at the choice of the software designer.  You could make the entire dataset fit in any given color space by ranging the numbers properly.

                 

                Dynamic range really has nothing to do with the gamut of a given color space...and as far as I know, there is no camera that can come anywhere NEAR filling up ProPhoto RGB since it actually contains "theoretical" that don't actually exist...as far as gamut mapping (not to be confused with luminance toning) being up to the developers of software, uh, no, sorry, there ARE industry standards regarding gamut mapping particularly relating to Relative Colorimetric which has a specific method. Perceptual mapping can be done but isn't currently supported in ICC V2 profiles for display based color spaces...

                1 person found this helpful
                • 5. Re: Pet Peeve:  Loss of Data on Conversion to other than ProPhoto RGB
                  JimGoshorn Level 2

                  Jeff,

                   

                  Do you happen to know where v4 profile support fall on Apple's, Adobe's and Epson's radar?

                   

                  I read this posting which said that v4 profiles are a problem when printing in Snow Leopard:

                   

                  http://tiny.cc/dxoot

                   

                  Jim

                  • 6. Re: Pet Peeve:  Loss of Data on Conversion to other than ProPhoto RGB
                    Hudechrome-sd9sPI Level 2

                    Jim, your link has this warning when clicked:


                    Warning, this link may harm your computer: http://tiny.cc/dxoot

                     

                    AVG found it to be unsafe or unknown.

                    • 7. Re: Pet Peeve:  Loss of Data on Conversion to other than ProPhoto RGB
                      Level 4

                      Well, Noel, of course you're going to lose some colors when going from a wider to a narrower color space.  It's not rocket science.

                       

                      WS12.gif LabGamut.gif WS00.gif WS14.gif

                      The red outline represents the L*a*b Gamut.

                       

                      EDIT:  The images are © by Bruce Lindbloom, from his web site:

                      http://www.brucelindbloom.com/index.html?WorkingSpaceInfo.html

                      • 8. Re: Pet Peeve:  Loss of Data on Conversion to other than ProPhoto RGB
                        Jeff Schewe Level 5

                        JimGoshorn wrote:

                         

                        Do you happen to know where v4 profile support fall on Apple's, Adobe's and Epson's radar?

                         

                        Well, V4 profiles sound good on paper but...nobody from the ICC has really pushed the whole spec into final form acceptable to the vast majority of companies involved in the ICC...so, I think V4 profiles that can contain and use proprietary Perceptual rendering intents is still far from an agreed upon standard...sorry I can give you better news...personally I WOULD like to use a Perceptual transform when going from PP RGB to sRGB when doing web work...

                        • 9. Re: Pet Peeve:  Loss of Data on Conversion to other than ProPhoto RGB
                          Level 4

                          Jeff Schewe wrote:

                           

                          …there is no camera that can come anywhere NEAR filling up ProPhoto RGB since it actually contains "theoretical" that don't actually exist...

                           

                          A very timely reminder of this plain fact.  Thank you.

                           

                          Hence the saying that "ProPhoto RGB is the only color space real men use".

                           

                          The key is to know the implications of using ProPhoto RGB and knowing how to deal with them.

                          • 10. Re: Pet Peeve:  Loss of Data on Conversion to other than ProPhoto RGB
                            Noel Carboni Level 7

                            "Not rocket science"...  Nice.  It seems they have you believing the hocus pocus, too, Tai.

                             

                            I've noticed that people who understand color space and gamut tend to throw about color space and gamut terminology.  Just keep in mind that it does not make you seem unquestionable to someone who understands the stuff possibly even better than you do.

                             

                            There is nothing sacred about what color is assigned for given readings in a camera.  The approach being described where you convert into ProPhoto RGB (which amazingly retains all the data) then do a lossy conversion to sRGB explains it all...  Following up with a claim that such a conversion can't help but lose data is bogus in light of the fact that the conversion did not need to happen in the first place (does no one else see this?).  And your statement, Jeff, that dynamic range has nothing to do with color space made me laugh.  Who determines the endpoints of a tone curve?  Federal law? 

                             

                            The objective must be to make the best image possible out of the captured data.  Trashing ART in the name of SCIENCE doesn't a good product make.  And hey, if you want to talk about strict adherence to math and theory, we can have a discussion about how wrong the colors come out.  THE VERY FACT that there are multiple profiles PROVES there is not just one "mathematically perfect" way to do this.  I have no idea how Adobe can on one hand claim the benefits of a "Recovery" function while on the other openly choosing to use an algorithm that clips data internally.  Theoretically accurate?  With S-shaped tone curves and 100 sliders and multiple profiles?  Give me a break!

                             

                            Let's look at the big picture, shall we?

                             

                            As an example, my camera captured some low, but non-zero, levels of red color (e.g., in the blue shirt in the raw image I posted above).  A raw conversion to sRGB just jams those red channel values to black.  Go ahead, try it for yourself.

                             

                            My camera did NOT underexpose.  The red channel is clipped to black.  The converter lost the data, plain and simple.  It's bonkers to claim that this is somehow "correct" behavior.  Doing so while hiding behind obfuscating terminology that less than 1% of the people understand is reprehensible.

                             

                            Honestly, I really didn't expect to be debated on the FACTS here.

                             

                            Color space makes no sense until after an image is developed.  It is a blatently circular argument to claim that the camera captured a color outside a gamut just because the converter threw away the data during an internal operation.

                             

                            Jeff, quite honestly the old saying "The operation was a success but the patient died" comes to mind.  You seem to really believe that the approach is valid and the conversion was a success, blissfully ignoring the fact that the image died.

                             

                            Perhaps it's time to move on to better methods?  People who believe they have a perfect solution don't innovate.

                             

                            I should think the Marketing people at Adobe would be interested in making the product actually work better for real world users.  I do hope they drop by here.

                             

                            Y'know how, a few versions back, you fixed Brightness/Contrast to not clip, but to roll off instead?  Hint hint!  Hell, make it an option if you still want to offer a mode to make people who photograph color charts and count photons happy too.

                             

                            Hey, I have a decent workaround, in the form of my own action, so it's no real skin off my nose if you don't want to improve your product.  This just serves to differentiate my work from that of the rest of the world who are losing data in THEIR sRGB conversions.

                             

                            -Noel

                            • 11. Re: Pet Peeve:  Loss of Data on Conversion to other than ProPhoto RGB
                              Level 4

                              There is absolutely no reason to make this discussion personal.  Throwing around insults and condescending sentences and phrases disqualifies whatever argument you were attempting to make. 

                               

                              I'll pass.

                               

                               

                              Wo Tai Lao Le

                              我太老了

                              • 12. Re: Pet Peeve:  Loss of Data on Conversion to other than ProPhoto RGB
                                Level 4

                                Noel Carboni wrote:

                                 

                                …so it's no real skin off my nose if you don't want to improve your product. 

                                 

                                Disclaimer:  I have no connection to Adobe whatsoever.

                                 

                                 

                                Wo Tai Lao Le

                                我太老了

                                • 13. Re: Pet Peeve:  Loss of Data on Conversion to other than ProPhoto RGB
                                  Noel Carboni Level 7

                                  By the way, you speak as though you are actually engineering the product, Jeff, yet I don't see an "employee" notation near your name...  Are you really involved with Camera Raw development or do you just heckle here like the rest of us?

                                   

                                  -Noel

                                  • 14. Re: Pet Peeve:  Loss of Data on Conversion to other than ProPhoto RGB
                                    Noel Carboni Level 7
                                    function(){return A.apply(null,[this].concat($A(arguments)))}

                                    Tai Lao wrote:

                                     

                                    There is absolutely no reason to make this discussion personal.  Throwing around insults and condescending sentences and phrases disqualifies whatever argument you were attempting to make. 

                                     

                                     

                                    Insults?  You find it insulting that I should claim I might understand color space at your level?

                                     

                                    I mean no insults here, and I'm sorry if any offense has been taken.

                                     

                                    I am also not intimidated, because I do have half a brain (I actually used to have more...)

                                     

                                    -Noel

                                    • 15. Re: Pet Peeve:  Loss of Data on Conversion to other than ProPhoto RGB
                                      Jeff Schewe Level 5

                                      Noel Carboni wrote:

                                       

                                      The converter lost the data, plain and simple.

                                       

                                       

                                      No...the COLOR SPACE lost the data, plain and simple...you are obsessing about color that is way, WAY firggin' outside the color space of sRGB and somehow you blame Camera raw...nope, sorry...you haven't gotten it yet...if you want to co tain ALL the colors your camera can capture the ONLY color space you can use is Pro Photo RGB...the fact that no display nor any printer can print the entire PP RGB color space is not the issue...and yes, if you want to obsess over getting each and every color you camera captured stuffed inside of sRGB, good *******' luck!!!!!

                                      • 16. Re: Pet Peeve:  Loss of Data on Conversion to other than ProPhoto RGB
                                        Level 4

                                        Noel Carboni wrote:

                                         

                                        By the way, you speak as though you are actually engineering the product, Jeff, yet I don't see an "employee" notation near your name...  Are you really involved with Camera Raw development or do you just heckle here like the rest of us?

                                         

                                        -Noel

                                         

                                        Not to presume I can speak for Jeff Schewe, but I will reply here in a manner that Mr. Schewe probably cannot:

                                         

                                        Yes, Jeff Schewe has considerable input into the Camera Raw team and works closely with them.  He's been responsible for at least planting the seeds of some of the ACR features.

                                         

                                        Additionally, Jeff Schewe literally wrote THE book on Camera Raw:

                                         

                                        http://www.amazon.com/Real-World-Camera-Adobe-Photoshop/dp/0321580133/ref=sr_1_1?ie=UTF8&s =books&qid=1238313549&sr=8-1

                                         

                                        I would suggest you calm down before you further embarrass yourself.

                                        • 17. Re: Pet Peeve:  Loss of Data on Conversion to other than ProPhoto RGB
                                          Level 4

                                          Noel Carboni wrote:

                                           

                                          Insults?  You find it insulting that I should claim I might understand color space at your level?

                                           

                                           

                                          You actually professed to understand color theory above my level.  You do not, sir.

                                           

                                          Noel Carboni wrote:

                                           

                                          I mean no insults here, and I'm sorry if any offense has been taken.

                                           

                                          Apology cheerfully accepted.  I mean no offense either, sorry if you took offense.

                                           

                                           

                                          Wo Tai Lao Le

                                          我太老了

                                          • 18. Re: Pet Peeve:  Loss of Data on Conversion to other than ProPhoto RGB
                                            Jeff Schewe Level 5

                                            Noel Carboni wrote:

                                             

                                            By the way, you speak as though you are actually engineering the product, Jeff, yet I don't see an "employee" notation near your name...  Are you really involved with Camera Raw development or do you just heckle here like the rest of us?

                                             

                                            Hum, how to answer...

                                             

                                            I work with Adobe....I don't work for Adobe.

                                             

                                            I have licensed technology to Adobe for inclusion in Camera Raw and Lightroom (output sharpening from PixelGenius) and I've worked directly with Thomas Knoll and Mark Hamburg under contract with Adobe for consulting on sharpening in Camera Raw and Lightroom...no, I don't write the code...the really bight boys like Eric Chan, Thomas Knoll and Zalman Stern to the hard work.

                                             

                                            But yes, indeed I do have a personal hand in and input towards making Camera Raw (and Lightroom which was hatched in my studio in Dec 2003) as good as it can be. Oh, yeah, as mentioned above, I have written a book about Camera Raw–actually I've just finished the 3rd edition I've been involved with, Real World Camera Raw for Photoshop CS5 which should be out in June...you might learn a thing or two.

                                             

                                            So, no, I don't hang out here to heckle you...that's a side benefit!

                                            • 19. Re: Pet Peeve:  Loss of Data on Conversion to other than ProPhoto RGB
                                              Noel Carboni Level 7

                                              Checking...  Nope, still not intimidated.    Good try though.  I'll continue to call 'em as I see 'em.

                                               

                                              And I can assure you I've been calm this whole time.  Never once left my chair. 

                                               

                                              I appreciate all your input.  The key piece of info that tied it all together was Jeff's note:  "Camera Raw, when it first opens an image, does a camera color to Pro Photo RGB primaries conversion for the Camera Raw processing pipeline".  That's where the data is lost, and it confirms my strategy.

                                               

                                              Oh, and lastly I guess since I do convert to ProPhoto RGB, then manipulate the data for my needs, I am a "Real Man", Tai.

                                               

                                              -Noel

                                              • 20. Re: Pet Peeve:  Loss of Data on Conversion to other than ProPhoto RGB
                                                Jeff Schewe Level 5

                                                Noel Carboni wrote:

                                                 

                                                The key piece of info that tied it all together was Jeff's note:  "Camera Raw, when it first opens an image, does a camera color to Pro Photo RGB primaries conversion for the Camera Raw processing pipeline".  That's where the data is lost, and it confirms my strategy.

                                                 

                                                No, sorry, you still don't get it.

                                                 

                                                Every single color and tone from your original capture is there in Camera Raw depending on what you do with it after Camera Raw. Do you get that? ALL THE COLOR FROM YOUR ORIGINAL CAMERA COLOR IS STILL THERE...can I say that any louder?

                                                 

                                                All of you camera color is there...what _IS_ lost is lost due to the color conversion from Pro Photo RGB to sRGB. That's where color that is outside of the color gamut of sRGB is clipped...and the primary reason for that clipping/loss is the fact that display based color space transforms are in Relative Colorimetric because Perceptual mapping isn't supported...

                                                 

                                                Do you get that? You are asking for Perceptual mapping which doesn't exist yet (and won't till V4 profile support).

                                                 

                                                Ok?

                                                 

                                                Can we at least get on the same page here?

                                                 

                                                Careful how you answer because your credibility is now at stake...being ignorant can be overcome by education...being stupid is unforgivable.

                                                • 22. Re: Pet Peeve:  Loss of Data on Conversion to other than ProPhoto RGB
                                                  Noel Carboni Level 7

                                                  Yeah, I made an incomplete quote and neglected the conversion to sRGB part.  I got it.

                                                   

                                                  Thank you for your insights, Jeff.  Assuming Perceptual mapping will get the job done, then that's what we'll have to wait for.  I'm glad its being worked on.

                                                   

                                                  We'll have to agree to disagree - for now - about getting fully on the same page.  As far as "getting it" I can assure you I FULLY understand color spaces and everything you've been saying, but given my background I have a different perspective on the whole thing than you do.  Clearly where I don't agree is on what the "givens" are in the problem.  I imagine if I'd been through the whole Camera Raw converter development I might see things more your way, but my background is different.

                                                   

                                                  But that's okay, last I looked there's room in the world for both of us.

                                                   

                                                  Good night, sirs, I'm done for the day.

                                                   

                                                  -Noel

                                                  • 23. Re: Pet Peeve:  Loss of Data on Conversion to other than ProPhoto RGB
                                                    Level 4

                                                    Noel Carboni wrote:

                                                     

                                                    The key piece of info that tied it all together was Jeff's note:  "Camera Raw, when it first opens an image, does a camera color to Pro Photo RGB primaries conversion for the Camera Raw processing pipeline".  That's where the data is lost, …

                                                     

                                                    You insist on denying the laws of physics and color theory, sir.  

                                                     

                                                    No camera can capture anything that could remotely be outside of the ProPhoto RGB gamut.  None.

                                                     

                                                    Thomas Knoll, creator of both Photoshop and Camera Raw wrote"

                                                     

                                                    "Camera Raw uses both RIMM and ROMM in its processing path (ignoring the gamma encoding). After the white balance and initial camera profile application, the data is basically in RIMM space. The tone curve and other user controls transform the image into ROMM space, which is then converted to the final selected RGB working space.


                                                    The big difference is RIMM is *input* (or scene) referred, and ROMM is *output* referred. Otherwise, they are really the same color space. Most of the controls that raw converters have are control knobs for the process of converting scene referred data to output referred data."

                                                     

                                                    Emphasis on "The tone curve and other user controls transform the image into ROMM space, which is then converted to the final selected RGB working space."

                                                     

                                                    It is the final selected RGB working space that dictates the loss of colors outside its gamut.

                                                     

                                                    Noel Carboni wrote:

                                                     

                                                    … it confirms my strategy.

                                                     

                                                    Quite the opposite, sir.

                                                     

                                                    You might want to stop this nonsensical vendetta, sir.

                                                    • 24. Re: Pet Peeve:  Loss of Data on Conversion to other than ProPhoto RGB
                                                      Jeff Schewe Level 5

                                                      Noel Carboni wrote:

                                                       

                                                      Thank you for your insights, Jeff.  Assuming Perceptual mapping will get the job done, then that's what we'll have to wait for.  I'm glad its being worked on.

                                                       

                                                      Now that you indicate you do indeed understand, then I'll tell you where you CAN download V4 sRGB color space profiles that do include Perceptual rendering intent mapping that might actually help your quest to get better sRGB image files...see: http://www.color.org/srgbprofiles.xalter.

                                                       

                                                      You can download the beta sRGB V4 profile that will allow a beta Perceptual rendering from ProPhoto RGB to sRGB using Profile to Profile transforms. It may actually help you eventual goal of getting better sRGB output.

                                                      • 25. Re: Pet Peeve:  Loss of Data on Conversion to other than ProPhoto RGB
                                                        Level 4

                                                        Noel Carboni wrote:

                                                         

                                                        Assuming Perceptual mapping will get the job done, then that's what we'll have to wait for.

                                                         

                                                        Then why on Earth are you not outputting your raw conversion from ACR into Adobe ProPhoto RGB and then use Photoshop to do a conversion to sRGB with a Perceptual Rendering Intent?  It can be easily automated and applied in batches.

                                                         

                                                        You don't have to wait for anything at all.

                                                         

                                                         

                                                        Hence the saying that "ProPhoto RGB is the only color space real men use".  

                                                         

                                                         

                                                        Cheerfully,

                                                         

                                                        Wo Tai Lao Le

                                                        我太老了

                                                        • 26. Re: Pet Peeve:  Loss of Data on Conversion to other than ProPhoto RGB
                                                          Level 4

                                                          I see Mr. Schewe beat me to it.   

                                                          • 27. Re: Pet Peeve:  Loss of Data on Conversion to other than ProPhoto RGB
                                                            xbytor2 Level 4

                                                            Then why on Earth are you not outputting your raw conversion from ACR into Adobe ProPhoto RGB and then use Photoshop to do a conversion to sRGB with a Perceptual Rendering Intent?  It can be easily automated and applied in batches.

                                                             

                                                            This is actually what I do when I get a chance to  do anything other than write stuff _for_ PS. I'm usually happy with the  results but one thing I've been meaning to research is other ways get ProPhoto colors into an sRGB space. There are times when I need a couple more knobs.

                                                             

                                                            I look forward to testing out the v4  profiles. Thanks for the link, Jeff.

                                                            • 28. Re: Pet Peeve:  Loss of Data on Conversion to other than ProPhoto RGB
                                                              Level 4

                                                              xbytor2 wrote:

                                                               

                                                              …ways get ProPhoto colors into an sRGB space…

                                                               

                                                              You are always going to lose some colors when bringing ProPhoto colors into sRGB.  Always.

                                                               

                                                              The question is whether you want to clip the out-of-gamut colors (Relative Colorimetric) or compress them (squeeze them) as in Perceptual rendering intent.

                                                               

                                                              http://www.photozone.de/color-theory-glossary

                                                               

                                                              Either way, you will change (some of) the colors.

                                                               

                                                               

                                                              Wo Tai Lao Le

                                                              我太老了

                                                              • 29. Re: Pet Peeve:  Loss of Data on Conversion to other than ProPhoto RGB
                                                                Level 4

                                                                Noel Carboni wrote:

                                                                 

                                                                I've put a Canon EOS-40D raw image online that can be used to demonstrate black point clipping in the red channel.

                                                                 

                                                                http://images.ProDigitalSoftware.com/IMG_1775.CR2

                                                                 

                                                                The image serves to illustrate what everyone has been saying, namely that sRGB is a narrower space.  That is clear.

                                                                 

                                                                AAAAA_Output_comaprison.jpg

                                                                Command+Click (Mac, Firefox) to open image at larger size in a new web browser tab

                                                                 

                                                                 

                                                                The narrower final output space gamut dictates the clipping observed in sRGB.  It's that simple.

                                                                 

                                                                If you must work in sRGB, output the ACR conversion into Adobe ProPhoto then convert to sRGB using perceptual rendering intent.  The beta V4 profile might help a little bit further.  I can't say for certain, as I have not done it myself, having no need for sRGB images.

                                                                 

                                                                You might want to compare the results to what you obtain with your custom action.  If you do, please post your conclusions here.

                                                                 

                                                                 

                                                                 

                                                                Wo Tai Lao Le

                                                                我太老了

                                                                • 30. Re: Pet Peeve:  Loss of Data on Conversion to other than ProPhoto RGB
                                                                  Bill_Janes Level 2

                                                                  Noel Carboni wrote:

                                                                   

                                                                  Oh, so you're telling me that a new camera model, one that has, say, 2 stops more dynamic range than a current model which just happens to fill the ProPhoto RGB color space from dark to light, will not fit, and Camera Raw will simply clip both ends even when converting to ProPhoto RGB?

                                                                   

                                                                  I doubt it.


                                                                  The mapping of the brightness levels to fit the color space is completely at the choice of the software designer.  You could make the entire dataset fit in any given color space by ranging the numbers properly.

                                                                   

                                                                  I'm not talking about converting from sRGB to ProPhoto RGB here, I'm talking about the initial assignment of converted data into a color space.

                                                                   

                                                                  -Noel

                                                                   

                                                                  You have to understand that you can experience two types of clipping Camera Raw (or any other raw converter): Luminance Clipping and Saturation Clipping. With luminance clipping, all 3 color channels are clipped and you will have a while spike or shoulder at the left or right end of the histogram. With saturation clipping, only one or two channels are clipped. With the latter, you are attempting to express very saturated colors at very low or very high luminances, and clipping will occur if the color space is not sufficiently wide to encode the RGB values. The process is easier to understand with the CIE L*a*b space where luminance and color are separated.

                                                                   

                                                                  Shown below are 3 dimensional plots of the ProPhotoRGB space (wire frame) and sRGB space (solid). They have the same dynamic range in that black can be mapped to RGB (0, 0, 0) and white to (255, 255, 255). A characteristic of RGB color spaces is they have the widest color gamut at mid luminaces (L* = 50) and have a double conical shape that contracts to a point at the highest and lowest luminances (L* = 0 and L* = 100). This property is much more marked for sRGB than ProPhotoRGB.

                                                                   

                                                                  In your example image (IMG_1775.CR2), the camera has captured the complete dynamic range of the image and black can be mapped to L* of 0 and white to L* of 1.0, corresponding to RGB values of 0, 0, 0 and 255, 255, 255 respectively. When you render your image into sRGB, problems arise with saturated reds at low luminance: they will not fit into the sRGB space. If you increase exposure in ACR to +4 EV, the luminance of these reds will be raised to values that fit into sRGB and the clipping can be nearly eliminated but then the overal image is too light. What you need to do is to render into a space that can encode reds at very low luminance.

                                                                   

                                                                   

                                                                   

                                                                  Gamuts.png

                                                                  sRGB_exp0.png

                                                                  sRGB_expPlus4.png

                                                                  • 31. Re: Pet Peeve:  Loss of Data on Conversion to other than ProPhoto RGB
                                                                    Noel Carboni Level 7

                                                                    Thank you everyone.

                                                                     

                                                                    I never intended this to be a thread fixated on color space conversions, resulting in loss of out-of-gamut colors.  It's quite clear that with certain things taken as givens, the information captured in a raw file cannot be represented in sRGB or other limited color spaces.  I knew that before I started.

                                                                     

                                                                    I am questioning the assumption that a strict adherence to the limitations of a color space is required every time.

                                                                     

                                                                    Please try to let that sink in.

                                                                     

                                                                    I already have a fine solution involving conversion to ProPhoto RGB then manipulation of the data to fit the sRGB space (with appropriate shifts in some colors to MAKE it fit).  You may say that it makes the color less ACCURATE.  I say it makes the image more ARTFUL and USEFUL.

                                                                     

                                                                    I understand color spaces.  My plugins are all properly color-managed, so if you're working in ProPhoto RGB you'll see a proper display.

                                                                     

                                                                    My whole point:  It would be good to have an option in ACR to MAKE all the colors captured by any given camera FIT THE TARGET COLOR SPACE without having to go through a separate step.  Perhaps the v4 Perceptual profiles will provide this (I will study them further).

                                                                     

                                                                    Please understand that my main focus is on the usefulness of the data in the developed image, not on the technical mechanics of how raw data is manipulated to get there.

                                                                     

                                                                    -Noel

                                                                    • 32. Re: Pet Peeve:  Loss of Data on Conversion to other than ProPhoto RGB
                                                                      Level 4

                                                                      Again, what you wish for goes against the laws of physics. Please let that sink in.

                                                                       

                                                                      No matter how you squeeze, compress, distort or invent colors, any out of gamut colors will be changed or eliminated when going to a narrower color space.

                                                                       

                                                                      No one is disputing your right to produce more pleasing or "artful" images.  That just isn't within the scope of a raw converter when outputting to such a narrow space as sRGB.

                                                                       

                                                                      Not having any need whatsoever for sRGB images myself, I can't even conceive of why you would choose to work in sRGB unless you're outputting your images for the web.  If that is the case, color accuracy is the least of your concerns.

                                                                       

                                                                       

                                                                      Wo Tai Lao Le

                                                                      我太老了

                                                                      • 33. Re: Pet Peeve:  Loss of Data on Conversion to other than ProPhoto RGB
                                                                        Hudechrome-sd9sPI Level 2

                                                                        If one wants to mess with colors other than strictly the givens in ACR, then try this:

                                                                         

                                                                        http://www.color.org/scene-referred.xalter#profiles

                                                                         

                                                                        It's difficult and at times, downright nasty results obtain. It also can produce stunning variations, variations that I wanted to see in the first place and could not otherwise reach. In other instances, it informed me of interpretations I hadn't conceived. It's notable the insistence of starting with ProPhoto as the color space of origin.

                                                                         

                                                                        After a reasonable mastering of the process, you can adventure out with respect to the starting values set in ACR.

                                                                         

                                                                        Noel, it is particularly good at pulling the lower value colors into a better space.

                                                                         

                                                                        FWIW, when I posted this link a while back, I was warned against it. In that spirit: Caveat emptor!

                                                                         

                                                                        And while I am at it, don't try to make popcorn while reading this stuff!

                                                                        • 34. Re: Pet Peeve:  Loss of Data on Conversion to other than ProPhoto RGB
                                                                          Level 4

                                                                          Noel Carboni wrote:

                                                                           

                                                                          I never intended this to be a thread fixated on color space conversions, resulting in loss of out-of-gamut colors.  It's quite clear that with certain things taken as givens, the information captured in a raw file cannot be represented in sRGB or other limited color spaces.  I knew that before I started.

                                                                           

                                                                          Then the title you gave to this thread is utterly incomprehensible.

                                                                           

                                                                           

                                                                          Wo Tai Lao Le

                                                                          我太老了

                                                                          • 35. Re: Pet Peeve:  Loss of Data on Conversion to other than ProPhoto RGB
                                                                            Noel Carboni Level 7

                                                                            Tai, you are being pretty thick on this.

                                                                             

                                                                            >any out of gamut colors will be changed

                                                                             

                                                                            Well DUH!  That's EXACTLY what I am requesting!

                                                                             

                                                                            What would be most useful is for them to be changed in such a way that no color channel detail is ever lost.  No matter whether the subject is a really dark blue color or a really bright red color, I want an option where all the data the camera captured can be squeezed to fit the color space.  When I look at the histogram I don't want to see data climbing the left or right side depending on whether I've selected ProPhoto RGB or another space.  THIS IS NOT HARD TO UNDERSTAND if you stop holding onto a few things that for whatever reason you're assuming MUST be kept as givens.

                                                                             

                                                                            In short I would prefer deep dark blue to become dark gray-blue rather than dark blue with no red channel data.  THIS IS NOT FUNDAMENTALLY DIFFERENT IN CONCEPT from recovering near-overexposure by turning the texture gray.

                                                                             

                                                                            And regarding the thread title:  Read "Conversion" as "Raw Conversion", not "Color Space Conversion".  I apologize for any confusion on that.  I should have said "Raw File Development" instead.

                                                                             

                                                                            -Noel

                                                                            • 36. Re: Pet Peeve:  Loss of Data on Conversion to other than ProPhoto RGB
                                                                              Level 4

                                                                              Also, consider the very first paragraph of your original post:

                                                                               

                                                                              Fact:  Camera Raw chooses to clip highlights and shadows for all color spaces other than ProPhoto RGB.

                                                                              [sic]

                                                                              • 37. Re: Pet Peeve:  Loss of Data on Conversion to other than ProPhoto RGB
                                                                                Hudechrome-sd9sPI Level 2

                                                                                What physical laws are being violated, Tai? There is no place for color in physics, save the differences in wavelength, which do not predict the results we see.

                                                                                 

                                                                                it's all in the brain.

                                                                                 

                                                                                My pet conjecture about what we see is that the visible color hides the true characteristics of the object illuminated, because what we see is what is reflected. The rest is absorbed, which in turn is dependent on the characteristics of the illuminant.

                                                                                • 38. Re: Pet Peeve:  Loss of Data on Conversion to other than ProPhoto RGB
                                                                                  Level 4

                                                                                  Noel Carboni wrote:

                                                                                   

                                                                                  Tai, you are being pretty thick on this.

                                                                                   

                                                                                  Sir, I don't know you from Adam, but if you persist on making this personal and feel compelled to resort to insults and personal attacks, my opinion of you is infinitely worse than yours of me.  Basic human decency compels me to refrain from further addressing you.

                                                                                   

                                                                                   

                                                                                  Wo Tai Lao Le

                                                                                  我太老了

                                                                                  • 39. Re: Pet Peeve:  Loss of Data on Conversion to other than ProPhoto RGB
                                                                                    Curt Y Level 7

                                                                                    Noel Carboni wrote:

                                                                                    My whole point:  It would be good to have an option in ACR to MAKE all the colors captured by any given camera FIT THE TARGET COLOR SPACE without having to go through a separate step.  Perhaps the v4 Perceptual profiles will provide this (I will study them further).

                                                                                     

                                                                                    Please understand that my main focus is on the usefulness of the data in the developed image, not on the technical mechanics of how raw data is manipulated to get there.

                                                                                     

                                                                                    -Noel

                                                                                    I have no skin in this discussion, so as a passive observer here is my take on the discussion.

                                                                                     

                                                                                    I  have been following these threads and I think the above statement by  Noel sums up his issues.

                                                                                     

                                                                                    He wants to bend the laws of physics to make the colors fit they way he thinks it should look (how can you MAKE the colors fit?).  This is fine as an artist, but from a technical standpoint it is wrong.  And this is where the rub is.  Tai and Schewe are looking at a techical solution that can be arrived at arithimetically.

                                                                                     

                                                                                    Therefore, the two concepts, artistic and mathmatical can not be the same solution.

                                                                                    1 2 Previous Next