Color Space Conversion but out of gamut color shift

Discussion in 'Digital Darkroom' started by geo_lam, Dec 26, 2010.

  1. Dear All,
    I am editing in ProPhoto colorspace and when preparing file to print in Fuji Frontier 570, I try to convert the color space from ProPhoto to sRGB. However, even I am using "Perceptual" in the conversion, the color still shift a lot. How can I remediate this?
     
  2. you might want to try some selective desaturation and/or exposure change to pull those colors back into sRGB gamut.
     
  3. Try converting to Adobe RGB instead of sRGB, and use "Relative Colorimetric" instead of "Perceptual" for rendering intent. If you're using your editor's color management, turn your printer's colormanagement routines.
    Disregard the "test" post...
     
  4. There should not be a color shift with a well built profile, in fact, converting from Adobe RGB (1998) or even sRGB to the output profile should produce very, very similar color appearance (you may want to try this). Are you seeing blues shifting magenta? As William said, try RelCol too (even Saturation). Where did this profile come from?
     
  5. I try to convert the color space from ProPhoto to sRGB...
    even I am using "Perceptual" in the conversion, the color still shift a lot.​
    There's no "perceptual" table in the matrix based sRGB color space unless you're converting using a table based Fuji Frontier custom profile which you have not indicated.
    You've missed something in describing what you are doing.
     
  6. There's no "perceptual" table in the matrix based sRGB color space unless you're converting using a table based Fuji Frontier custom profile which you have not indicated.​
    That’s exactly how you get a Perceptual rendering (from the output profile, not the source profile).All output (printer) profiles should have all 3 tables. By the time the output profile comes into the scene, its getting Lab from the PCS (from sRGB). If you conduct a matrix to matrix profile conversion, again, the secondary profile is being fed Lab, but it only has a colorimetric table, in which case what you wrote above would be true.
    The question now is, what kinds of shifting are being seen going from ProPhoto (or sRGB) to the Fuji output color space and why the Fuji is causing this shifting.
     
  7. I try to convert the color space from ProPhoto to sRGB​
    The OP is converting from ProPhoto to sRGB, not to a Fuji Output color space. As Tim pointed out, there is no perceptual conversion to a matrix color space, at least in Version 2 ICC profiles.
    However, I agree that you should not see color shifts. What should happen is that some colors get saturated or blow out, due to the smaller sRGB color space (unless this effect in the saturated colors is perceived as a color shift)
    Besides reducing saturation or, even better, reduce vibrance before converting to sRGB, another option is to use a version 4 sRGB, which do allow for perceptual conversion. You can find the profile here
     
  8. The way I read the OP’s question is he’s getting a shift form ProPhoto to Fuji. There’s no way a ProPhoto to sRGB conversion would produce a true color shift (I’ve never, ever seen this).
     
  9. A neutral or gray tone will not shift when converting from Prophoto to sRGB, but if you have a wide gamut monitor and an image in Prophoto with a large area with colors outside the gamut of sRGB, you may perceive a color shift when converting to sRGB, since that large area will have a less saturated color (it would be the most saturated available in the new color space)
     
  10. Well I just opened a Granger Rainbow built in Lab, converted to ProPhoto, then sRGB. I see no color shifts (viewing on a wide gamut, NEC 3090). There is of course a difference in perceived saturation and smoothens but nothing I see I would describe as a color shift, even in those notoriously difficult blues.
     
  11. The way I read the OP’s question is he’s getting a shift form ProPhoto to Fuji. There’s no way a ProPhoto to sRGB conversion would produce a true color shift (I’ve never, ever seen this).​
    You're probably reading too fast. Maybe too much coffee?
    I read something totally different. That's why I emphasized with the OP's own quotes and you still didn't catch that. I was going to make the same assumption as you that he's getting color shifts converting to the Fuji profile and NOT SRGB, which makes more sense, but I thought it would be better to have the OP clarify just so we're all on the same page.
     
  12. Again, there should be no such shifts from ProPhoto to sRGB. Now maybe this is a display issue, I don’t know but it seems far more likely to see a shift going from either working space to the output color space. We need the OP to clear this up for us and if it is ProPhoto to sRGB, I’d sure like a look at a low rez image to attempt this on my end cause its not something I’ve yet seen.
     
  13. Andrew, is it possible for someone to select a printer profile as their display profile? Just curious.
    I say this from my one consulting gig I had several years ago where their display of the PDI target was so screwed up there was no way a canned display profile was the cause. It was on a Windows XP system. It looked like a table based profile was loaded.
    He had an odd name for his display that was worded similarly to the name of the paper profile made by the $3000 ProfileMaker package a local university art professor happen to come by and build for him in the past.
    Later after I recalibrated with his SpyderPro 2 package, he mentioned he'ld been fiddling around changing display profiles and that's when things went wrong.
    I've never heard of it being possible to load into the video LUT a printer profile. Just wondered if that is possible on some systems. I know you can't do that on the Mac.
     
  14. sRGB is NOT the color space of the Fuji Frontier 570, regardless of what you've been told or led to believe. The color space is very specific to the print paper. Therefore, you should have a profile for the machine and paper type. Fortunately, I think you can find many of these at Drycreek and many of them are satisfactory even though they were not made from the machine in your neighborhood. You will learn you're going from one of the largest color gamuts to one of the smallest color gamuts. However, a PERCEPTUAL rendering should result in just that; PERCEPTUAL.
    There are relatively few color colors found in nature that may be lost in the Frontier print process. A classic example is a very bright synthetic sweater worn by a high school senior for her portrait. (A manmade fabric / dye combination, not found in nature.) Another classic example is a stack of brightly colored towels on sale at JC Penny. (Again, a manmade fabric / dye combination, not found in nature.) "Natural" scenes usually reproduce well from the Frontier.
     
  15. Andrew, is it possible for someone to select a printer profile as their display profile? Just curious.​
    That’s certainly possible.
     
  16. Andrew, is it possible for someone to select a printer profile as their display profile? Just curious.​
    It depends on CMM.
    In ICC profiles there is a "device class signature".
    "output class signature" is for printer profiles.
     
  17. Hi Andrew,
    Yes. It is a shift in saturation (actually is the blue) in the conversion from the ProPhoto to sRGB.
    The fuji lab cannot provide paper specific profile, so I am using an sRGB for preparing file to send to the lab.
    Besides, sRGB, what profile can I use?
     
  18. Yes. It is a shift in saturation (actually is the blue) in the conversion from the ProPhoto to sRGB.
    The fuji lab cannot provide paper specific profile, so I am using an sRGB for preparing file to send to the lab.
    Besides, sRGB, what profile can I use?​
    First, what you report doesn’t sound Kosher. You have the display calibrated, have proper profiles in use? Can you supply a small rez file we can convert from ProPhoto to sRGB? You may want to circle with a lasso and stroke the area where you see this shift.
    Second, you’d ideally be getting an output profile from the lab to do the conversions.
     
  19. Just a heads up and not sure if you all have already heard about this, but Fuji Frontiers are putting out what they call a dry process printer in some Walmarts. I just came back today from my local Walmart to check out their new photo lab after they renovated the whole store and they got rid of their lazer exposed silver halide printer. The head clerk at the counter said the new Fuji Frontier now prints inkjet. It's a much smaller printer by comparison.
    Saw some customer's sample snap shots and found there's a big improvement in skin tone rendering much like you see on Epson inkjets where there's a nice caramel hue in Caucasian skin tone instead of there typical (at this location) pinky peach handing them sRGB.
     
  20. Hi Andrew,
    The monitor is calibrated with Spyder2. The file is loaded from RAW in ProPhoto and edited.
     
  21. What do you see when you go back to the raw converter and select sRGB instead of ProPhoto?
     
  22. The link goes to a page saying the file was deleted.
     
  23. Hi Andrew,
    The file is attached in the post thread itself. File name as UpLoadColorSpace.tif
    Thanks.
     
  24. The link takes me to a web page with the image (some blue sky) but what color space is this in? What I’d really like is the TIFF with an embedded profile, is that what you’ve uploaded?
     
  25. Hi Andrew,
    Yes.
    I cropped the photo with just the affected background (colour shift after conversion to sRGB) which is the blue background. The file is in ProPhoto profile.
     
  26. It did come down in ProPhoto, good.
    When I use Convert to Profile and select sRGB, I see no visual difference at all.
     
  27. That is strange. I did see the blue shifted to lighter color and some purple appears.
    I am using PhotoShop convert to function, with perceptual/Relative colorimetric. MOnitor is a very old Eizo with default sRGB mode.
     
  28. I get a shift on my 2004 G5 iMac running OS 10.4.11 and calibrated with EyeOne Display. See below the screenshot that's kept in my monitor's space because converting to sRGB would cancel out the difference so view that screenshot in a color managed app/browser.
    It's probably a gamut issue with the display with mine being close to sRGB since Andrew who I'm assuming is using a wide gamut display says he doesn't get a shift.
    BTW convert to your display profile and see if you get a shift. I don't get a shift.
    00Xw8E-315743584.jpg
     
  29. Conclusion:
    Display gamut when even close to sRGB can clearly render that ProPhotoRGB blue,
    but sRGB 2.1 can't.
    Anyone have a better explanation, please divulge.
     
  30. Yes. In my case, I’m using an NEC 3090 wide gamut display. I see no color shifts. If there are differences, its visually insignificant. When I originally heard about the shift, I ought it was the old blue to magenta hue shift (which could still result going to the output profile). But based on what I’m seeing here, the ProPhoto to sRGB conversion isn’t worth a worry IMHO.
     
  31. If you look at the histogram, the Red channel takes a hit during the conversion. It's forced into clipping in the shadows and is suppressed to near nothing where it's not clipped. For example, before conversion, I get a level of R=41 when sampling in the midtone (~128) blue area. After conversion, Red becomes R=0 at the same point. The Blue channel gains about 30 points in the midtones as well.
    Having said all that, the change on the monitor is minimal, but it is there. (NEC P221W)
     
  32. But based on what I’m seeing here, the ProPhoto to sRGB conversion isn’t worth a worry IMHO.​
    And to add to that, there isn't a printer in the world with dye or pigment formulation that can reproduce that ProPhotoRGB blue that accurately anyway without having to resort to a toxic metal based ink formulation.
    And according to Howard's Red=0 there's no telling how far that causes the math under the hood to find bottom mapping the rest of the color relationships for that particular hue/saturation appearance. This is probably why this shift varies in different degrees according to the level of hue/sat chosen based on my own observations converting other similar colors from ProPhotoRGB to sRGB.
     
  33. And to add to that, there isn't a printer in the world with dye or pigment formulation that can reproduce that ProPhotoRGB blue that accurately anyway without having to resort to a toxic metal based ink formulation.​
    And there never will be, at least until we evolve into one of those Arthur C. Clark super babies and our vision exceeds today limitations of which two primaries defined in ProPhoto exceed <g>. They fall outside human vision (gamut). Such are the rules when synthetic RGB color spaces, based on match are created to be this large.
     
  34. Thanks all.
    What is the remedy for this out of gamut? Lower the saturation in several layers (desaturate a layer of -10 at a time)? or Make adjustment in curve layer to lower the red channel?
     
  35. If you're having the file printed locally, maybe you should try a test print to see if the result is pleasing to you (and note that pleasing and accurate are not always the same thing). Those of us who have to shoehorn RGB images into the CMYK color space learned to live with "pleasing" a long time ago. :)
    If you decide to correct with Curves, I'd do a global adjustment at the top of the layer stack and use a layer mask to shield areas that you don't want affected.
     
  36. What is the remedy for this out of gamut? Lower the saturation in several layers (desaturate a layer of -10 at a time)? or Make adjustment in curve layer to lower the red channel?​
    Edit with Soft Proof on with the printer's profile loaded on a copy of the background. Start out using Hue/Saturation tool and stay in 16 bit ProPhotoRGB. Tweak with curves the areas that might band/posterize if needed.
    Some printers printing to glossy paper can come close to one particular hue of blue that is close to what you want but kick up posterized banding transitioning into another blue that's close to it like in your gradient. Soft Proofing will usually show this bad transition. You can always do a test print first.
    I've been surprised by some printer's capability of reproducing gorgeous blues that I thought would clip to some dull, dark cyan or purple compared to the vibrant cobalt blue I saw on the display. The vibrant blue I got in print as Howard pointed out wouldn't be dead on accurate to the display but still looked vibrant.
     
  37. I downloaded the picture and converted it to sRGB on my MBP. The display shows the converted image with a very slight purple tint. The display is calibrated with ColorMunki.
     
  38. Francisco Disilvestro wrote:
    Besides reducing saturation or, even better, reduce vibrance before converting to sRGB, another option is to use a version 4 sRGB, which do allow for perceptual conversion. You can find the profile here
    The first paragraph of the linked article reads...
    The sRGB v4 ICC preference profile is a v4 replacement for commonly used v2 sRGB profiles. It gives better results in workflows that implement the ICC v4 specification. It is intended to be used in combination with other ICC v4 profiles.
    ...so the questions I'd like to ask, hoping someone would be able to clarify, are:
    • what other ICC v4 profiles are they talking about? -- monitor, printer, ??? -- how do I check and what if those other ICC profiles aren't v4?
    • is there any possible downside of using sRGB v4 (as opposed to the "default" v2), e.g., when saving for web?
    • do ProPhoto and Adobe RGB come in v4 as well? -- it doesn't say
    Thanks!
     
  39. Your best bet is to ignore V4 profiles for the time being, they are not ready for prime time. Even newer packages that make V4 profiles (i1Profiler for example) don’t fully support the V4 spec (there’s no PRMG support) so its a V2 profile in disguise. Without a full set (source to destination) fully implemented V4 profile, nothing is gained. And a number of applications have issues with V4 profiles depending on OS and print driver.
     
  40. Much appreciated, Andrew!
    In a sense, that's a good news because I'm off the hook without feeling guilty that there is something I should be doing, or the uncomfortable feeling that instead of improving things I might be actually getting them worse by neglecting the if it ain't broken, don't fix it "wisdom," which is what I've already done -- need to revert back to sRGB IEC61996-2.1
    ...or should I instead use one of the new v2 sRGB profiles? -- I've read the latter half of the ICC article on the sRGB profiles (quoted below) and the statement that the 'black scaled' profile has the preferred rendering intent in the header set to 'perceptual' confuses me as my understanding has been that v2 profiles don't support perceptual intent (?)

    I use Relative Colorimetric intent with Black Point Compression, so I gather the 'no black scaling' profile would be more appropriate for me because:
    (a) it has the preferred rendering intent in the header set to 'relative colorimetric'; and
    (b) it can be used with BPC 'on' or 'off' in the CMM, and if it is used with BPC 'on' the results should be the same as when using the 'black scaled' profile;
    however, I thought I'd better confirm my half-educated guess with someone in-the-know.
    sRGB profiles: v2 profiles @ http://www.color.org/srgbprofiles.xalter

    Two ICC version 2 (v2) sRGB profiles are provided, one with XYZ black point scaling to zero, and one without. The 'black scaled' profile has the preferred rendering intent in the header set to 'perceptual'. and the 'no black scaling' profile has the preferred rendering intent in the header set to 'relative colorimetric'.

    Both profiles contain the standard linearized Bradford D65 to D50 chromatic adaptation tag (this tag was often not present in older sRGB profiles), and the media white point tag is set to D50 (as is required for ICC v4 profiles). This avoids the inappropriate color casts that older sRGB v2 ICC profiles sometimes produced when the absolute colorimetric intent was used.

    The 'black scaled' profile will work correctly when either Black Point Compensation (BPC) is on in the CMM/application, or the other profile transform to be used for the conversion is also black scaled. Black scaled profiles are needed when BPC is desired for the conversion but the CMM to be used does not support BPC. Most v2 sRGB profiles in current use are black scaled because they are intended to be used as the source profile in conversions where the destination profile perceptual intent will be used (v2 perceptual transforms typically include black scaling).

    The 'no black scaling' profile produces sRGB colorimetry in the PCS that is more accurate to what a viewer of a sRGB calibrated display will observe in the reference sRGB viewing conditions. This is the case when the display has been calibrated to include the viewer-observed black level such as one might achieve with a non-contact monitor calibrator or other means to include ambient effects. It should be used in situations where greater colorimetric accuracy is desired, e.g. as the destination profile for preview on calibrated sRGB displays where the viewer-observed black has been included. However it should be noted that most current LCD displays, even those that use the sRGB primaries and gamma, have a higher white point luminance and dynamic range than the sRGB reference display. To produce accurate preview colorimetry on these displays they should be accurately profiled, instead of using an sRGB profile.

    The 'no black scaling' profile can be used with BPC on or off in the CMM. If it is used with BPC on the results should be the same as when using the 'black scaled' profile. If it is used with BPC off it will produce un-black-scaled media-relative colorimetry: if the source encoding has tones darker than the destination encoding black point they will be clipped, and if the source black point is higher than the destination black point the source black point will be accurately reproduced.​
    Any suggestions?
     
  41. V2 matrix profiles do not support a Perceptual intent (there’s no such table in them). You’d be getting a Relative Colorimetric intent. BPC is an option if the CMM supports it (ACE of course does).
     
  42. That's what I though. Does it mean that you'd also agree with my inference that I should use sRGB_IEC61966-2-1_no_black_scaling.icc rather than the sRGB_IEC61966-2-1_black_scaled.icc profile?
     
  43. If you use ACE, doesn’t matter as it supports BPC. You control if you want it or not via the BPC checkbox. That said, depending on the source space being mapped to sRGB, both options will provide an identical result. I always keep BPC on for all conversions.
     
  44. Yep, have Adobe (ACE) selected in the 'Engine' drop-down box, and have the BPC checkbox ticked "permanently" (as well as "Use Dither" and "Compensate for Scene-referred Profiles").
    I do conversion to sRGB as the next to the last step, just before changing the bit-depth to 8, mostly from ProPhoto (output from ACR and my PS default Working Space), potentially from LAB (if I make a detour that way).

    So, if I understand you correctly, you're saying it won't matter the least which of the two new profiles I pick, or perhaps even whether I stay with the one that came with my Mac, correct?
     
  45. I don’t believe there’s any difference but its easy to test. Do the conversions with each, then use the process described here to examine the data:
    http://digitaldog.net/files/Apply_Image.pdf
     

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