sRGB, Adobe RGB, and ProPhoto RGB - Exploring the Gamut Limitations of Printing

[digitaldog]

This approach may sound strange, but it is not wrong, under the premise a) that the printer's gamut is somewhat close to sRGB, and b) that the printer/lab do not run any ICC-type color space conversion before feeding the RGB data into the printer.

What's the old saying about 'close'? I've never seen an output profile I've built that's 'close' to sRGB. There are colors that fall outside sRGB and colors that don't. The shapes are vastly different. Anyway, a printer that doesn't run any ICC-type color space conversion still has to convert to the native output color space in some form. It might not use ICC profiles, but the printer doesn't produce sRGB. Some solutions, like ICC profiles are better than others.

[Doug Gray]

Yes, I see the point of your suggested approach, and no doubt it can be useful right in the context as described in post #49 by FranciscoDisilvestro.

But then it elevates the conversion from ProPhotoRGB to the printer profile - and its presumably more advanced gamut mapping / clipping algorithm - to a kind of general reference. Below is an example where I think it doesn't work out.

… since we were also talking about Fuji Frontier Printer along this thread:

--
Image #01:  was kept in ProPhotoRGB with out-of-sRGB marks, just to illustrate that there is a bunch out-of-sRGB colors/pixels to deal with.

Image #02:  was obtained by straight conversion from ProPhotoRGB to sRGB. As expected, and visible on my screen, the Hue gets slightly shifted towards yellow/orange, the red channel is clipped and fine details are getting somewhat blurred. That's not ideal, but we will see this is not the worst case.

Image #03:  was obtained by ReCol conversion from ProPhotoRGB to one of the Frontier Printer media profiles which Fuji Europe offers here for the Frontier Printer in so-called sRGB-mode.  Next, the image was converted RelCol to sRGB to ensure the comparability with the previous image #02.  This second conversion does not do a lot. The deterioration of the image happens with the first conversion.

Conclusion:  whatever RelCol-gamut-clipping-algorithm this printer profile uses, it is apparently worse here than the simple matrix math clipping. Image #03 is quite dark and the fine details got largely blurred. Further, I also tried one of the Fuji Frontier profiles from Dry Creek Photo, and the results are not really better.

Image #04 provides a cross check. The sRGB image #02 is converted RelCol to the Frontier Printer profile. Again the results are better than bumping into the printer profile directly with the ProPhotoRGB colors.

Image #05 shows the "semi-color-management approach" which Fuji once suggested in a corresponding paper (which is unfortunately not available on their site anymore).  The image in sRGB, #02, is soft-proofed to the printer profile with Preserve RGB Numbers enabled.  It was suggested to edit the sRGB image under this soft-proof before sending it to the lab.  This approach may sound strange, but it is not wrong, under the premise a) that the printer's gamut is somewhat close to sRGB, and b) that the printer/lab do not run any ICC-type color space conversion before feeding the RGB data into the printer.

It is entirely possible that converting first to sRGB would yield a better looking print that going direct from ProPhoto to printer. The outlined approach's only value is producing an sRGB rendering that models closely the full gamut print so it completely depends on how good the printer profile is at that. For an image already converted to sRGB, and pleasing in that space, there is no value in this additional process.

One of the issues in editing, even in a completely color managed operation, is that the monitor rendering itself, actually uses matrix conversion with clipping - an argument for the widest possible monitor gamut to more closely approximate the colors the printer profile works with.

As for the printer sRGB profile, I've not encountered that before. Seems weird.
Is the ProPhoto RGB portion available. It might be interesting to run it through my stuff here.

[digitaldog]

As for the printer sRGB profile, I've not encountered that before. Seems weird.

There is no such thing as an sRGB printer. The spec is based on a theoretical CRT circa 1994 or so with P22 phosphors. sRGB can be the source color space of data converted to a printer, that doesn't make that printer an sRGB printer as none exist.

[Doug Gray]

There is no such thing as an sRGB printer. The spec is based on a theoretical CRT circa 1994 or so with P22 phosphors. sRGB can be the source color space of data converted to a printer, that doesn't make that printer an sRGB printer as none exist.

Yes, clearly, which is why I find the notion weird. The closest I can imagine is that it's a "profile," using the term loosely, that converts a large space into the narrow sRGB space in such a way that it will somehow look good when submitted as an sRGB file on their printer. That goal doesn't seem to have been met.

Many colors that are in sRGB still can't be printed on anything. Maybe it smushes them. It sounds like a mess but I haven't read their docs on what the thing is supposed to do.

[digitaldog]

Yes, clearly, which is why I find the notion weird. The closest I can imagine is that it's a "profile," using the term loosely, that converts a large space into the narrow sRGB space in such a way that it will somehow look good when submitted as an sRGB file on their printer. That goal doesn't seem to have been met.

Well the point of my video is that sRGB is about the worst RGB working space to use for output to a printer, worse when it's vastly wider gamut but not so hot when smaller like a Lightjet etc. Of course the image data plays a role too. But one can and should (IF possible) send the image to a lab using sRGB and maybe Adobe RGB and see the results on the print. That's the final proof of what to use when you're got saturated imagery. As seen in the gamut maps I've provided, for the devices I profiled, Adobe RGB (1998) is a 'better' fit unless you're in the mood to clip colors.

[Peter_DL]

It is entirely possible that converting first to sRGB would yield a better looking print that going direct from ProPhoto to printer. The outlined approach's only value is producing an sRGB rendering that models closely the full gamut print so it completely depends on how good the printer profile is at that. ...

As for the printer sRGB profile, I've not encountered that before. Seems weird.
Is the ProPhoto RGB portion available. It might be interesting to run it through my stuff here.

The >> ICC Profile for Fuji Frontier Printer sRGB <<
which I used above was the Crystal Archive Paper Supreme HD, or, likewise with the Crystal Archive Digital Paper Type DP II.

--

[Doug Gray]

Well the point of my video is that sRGB is about the worst RGB working space to use for output to a printer, worse when it's vastly wider gamut but not so hot when smaller like a Lightjet etc. Of course the image data plays a role too. But one can and should (IF possible) send the image to a lab using sRGB and maybe Adobe RGB and see the results on the print. That's the final proof of what to use when you're got saturated imagery. As seen in the gamut maps I've provided, for the devices I profiled, Adobe RGB (1998) is a 'better' fit unless you're in the mood to clip colors.

What I hate about print labs that only take sRGB is that you have no idea what you are going to get. You can't expect them to match a color managed print process so a carefully created Photoshop print is probably not going to turn out like you want even if it looks semi-ok in sRGB. And different labs will produce different looking prints as they will all use their own secret sauce mapping sRGB in PerCol. Useful only for snaps you don't really care about.

[Doug Gray]

The >> ICC Profile for Fuji Frontier Printer sRGB <<
which I used above was the Crystal Archive Paper Supreme HD, or, likewise with the Crystal Archive Digital Paper Type DP II.

Thanks. What about the original image?

[digitaldog]

What I hate about print labs that only take sRGB is that you have no idea what you are going to get. You can't expect them to match a color managed print process so a carefully created Photoshop print is probably not going to turn out like you want even if it looks semi-ok in sRGB. And different labs will produce different looking prints as they will all use their own secret sauce mapping sRGB in PerCol. Useful only for snaps you don't really care about.

On that we are in violent agreement.

[Peter_DL]

What I hate about print labs that only take sRGB is that you have no idea what you are going to get. You can't expect them to match a color managed print process so a carefully created Photoshop print is probably not going to turn out like you want even if it looks semi-ok in sRGB. And different labs will produce different looking prints as they will all use their own secret sauce mapping sRGB in PerCol.

Myabe the Dry Creek Photo website helps.
quote: >>Frontier and Noritsu printers do not read embedded profiles<<. Hence there is no mystic PerCol conversion.

--

[digitaldog]

Myabe the Dry Creek Photo website helps.
quote: >>Frontier and Noritsu printers do not read embedded profiles<<. Hence there is no mystic PerCol conversion.

Depends on the front end settings used, certainly for Frontiers. I've built profiles in the past, for labs that had such devices and could use ICC Profiles going out to a Frontier. Of course recognizing the source color space inside the image data for the conversion.
EDIT Maybe not... see:


It doesn't matter if you embed ICC profile or not, Frontiers controller is ICC profile colour blind - it only increases the file size, so that why we may want to uncheck "embed ICC profile" while saving pre converted images.

Frontier has two working modes - sRGB (above mentioned), and PD. The second mode is more interesting from our perspective, as it is something like "ICM off" "no colour correction" known from printer drivers. It doesn't seem to proceed any limiting conversion, and allows us to utilise the whole gamut of c-print emulsion. As in sRGB mode case, we have to create/download profile created in PD mode, convert the image rendered to a large colour space, and enjoy much more saturated colours from blue-emerald-phtalogreen region, and better tonality (there's only one conversion, so there's less rounding errors). If you have a wide gamut display you can check the difference switching between sRGB and PD mode profiles
http://forum.luminous-landscape.com/index.php?topic=93016.new;topicseen#new


PD mode is what was used to create the ICC profiles but the targets (Depends on the front end settings used) were of course untagged as they always are.

[Doug Gray]

Frontier has two working modes - sRGB (above mentioned), and PD. The second mode is more interesting from our perspective, as it is something like "ICM off" "no colour correction" known from printer drivers.
....

Andrew,
Interesting.  I suppose one could send them profile patch images in PD, scan and make profiles, then check the consistency. Have people done this to your knowledge? I'd trust them more but wonder how much day to day variation their process experiences. Might be a good idea to include a small patch set in an order for QC purposes.

[Doug Gray]

Yes, I see the point of your suggested approach, and no doubt it can be useful right in the context as described in post #49 by FranciscoDisilvestro.

But then it elevates the conversion from ProPhotoRGB to the printer profile - and its presumably more advanced gamut mapping / clipping algorithm - to a kind of general reference. Below is an example where I think it doesn't work out.

… since we were also talking about Fuji Frontier Printer along this thread:

--
Image #01:  was kept in ProPhotoRGB with out-of-sRGB marks, just to illustrate that there is a bunch out-of-sRGB colors/pixels to deal with.

Image #02:  was obtained by straight conversion from ProPhotoRGB to sRGB. As expected, and visible on my screen, the Hue gets slightly shifted towards yellow/orange, the red channel is clipped and fine details are getting somewhat blurred. That's not ideal, but we will see this is not the worst case.

Image #03:  was obtained by ReCol conversion from ProPhotoRGB to one of the Frontier Printer media profiles which Fuji Europe offers here for the Frontier Printer in so-called sRGB-mode.  Next, the image was converted RelCol to sRGB to ensure the comparability with the previous image #02.  This second conversion does not do a lot. The deterioration of the image happens with the first conversion.

Conclusion:  whatever RelCol-gamut-clipping-algorithm this printer profile uses, it is apparently worse here than the simple matrix math clipping. Image #03 is quite dark and the fine details got largely blurred. Further, I also tried one of the Fuji Frontier profiles from Dry Creek Photo, and the results are not really better.

Image #04 provides a cross check. The sRGB image #02 is converted RelCol to the Frontier Printer profile. Again the results are better than bumping into the printer profile directly with the ProPhotoRGB colors.

Image #05 shows the "semi-color-management approach" which Fuji once suggested in a corresponding paper (which is unfortunately not available on their site anymore).  The image in sRGB, #02, is soft-proofed to the printer profile with Preserve RGB Numbers enabled.  It was suggested to edit the sRGB image under this soft-proof before sending it to the lab.  This approach may sound strange, but it is not wrong, under the premise a) that the printer's gamut is somewhat close to sRGB, and b) that the printer/lab do not run any ICC-type color space conversion before feeding the RGB data into the printer.

I didn't use the "sRGB" profile and used the Fuji Frontier HD PD profile to run the same tests I did on Andrew's image. The initial image has some high intensity ProPhoto Reds are outside Adobe RGB and even the Mac Adam gamut for reflective surfaces so there is no way to actually print those colors on any medium now, or in the future.  This is even true for the image obtained by only converting to sRGB though the clipping above 255 also reduces luminance together with a hue shift and flattening some areas.

Interestingly, the full gamut printable image is within the Adobe RGB space and only slightly outside the sRGB space. Consequently the image created by converting the original to printer space (big change) then sRGB results in almost no perceivable change from the print image. That said, printing using PerCol, instead of RelCol w BPC, produces a more pleasing print and, as with RelCol, the sRGB image of said print per the process is visually extremely close to the full gamut PerCol print image.

Here are the stats re printing using RC w BPC, dE's are in DeltaE2000:
To sRGB then to Printer Space then to sRGB Ave dE: 0.533, Max dE: 7.059
To Printer Space then to sRGB Ave dE:  0.397, Max dE: 4.545

[Stephen Ray]

If you haven’t already, I recommend downloading ALL the offered ICC profiles from the Fuji Europe link you posted earlier in this thread. If you’re going to such lengths, those profiles from those various machines using those various materials can provide very useful insight when compared against each other.

Examples:

1)  If you’re so concerned about sRGB, which is emissive, hold-and-compare sRGB against the Chromira Fuji Clear profile. The clear material is about as emissive as you will find. (It’s made to be backlit.) A more apples-to-apples comparison. You might also come to the realization that a Frontier IS NOT and RGB printer. (Nobody puts Fuji Clear in a Frontier, thus no profile.) The Frontier came to market way back in the 1990s before most people heard of an sRGB profile and before Photoshop could effectively soft proof for it for lack of a $400 Kodak plugin.

2)  Hold-and-compare Durst Lambda Fuji-CA-DPII_v3a against Chromira_FF_DPII_G_L. Two different printer technologies (Lambda is RGB lasers vs Chromira LED exposure system) but same media/RA4 process yet yielding very similar results on the Crystal Archive paper.

3)  Hold-and-compare Fuji_Frontier_DryLab4x0_PD_v3a against any other Fuji Frontier profiles. Very different technologies altogether. 

Further, you might find on the web ICC profiles offered by the few remaining shops who still operate Lightjets, Lambdas, and Chromiras. If you compare their profiles against these from Fuji, you will notice a trend that the media/process is very similar. Dare I say “close?” Commercial labs running Frontiers should show the same similarity. Costcos, maybe. Walmarts, maybe not so much. Walgreens, maybe assuredly not so much. Just due to calibration and chemistry control quality. 

Lastly, because I notice your dE measurements, I can tell you the larger color shops do not entirely count on ICC profiles for all their color matching. Critical colors are specified by Pantone guides, usually. The better RIPS offer a feature to lookup color substitution recipes. If the orange flower petal against the blue sky doesn’t match the client’s orange sweater apparel for this holiday season in-store graphics within a VERY certain dE, an operator selects the flower petal and tweaks a curve to predetermined values from using a printed Pantone chart. Also, the client is experienced enough not to have manufactured a product with colors that their advertising could not reproduce.

Mother Nature, she’s more of a challenge and we’re back to the flower.

[Doug Gray]

So, the process to produce the closest match of a print to either an sRGB or aRGB (Adobe RGB (1998)) needs to be done carefully. It assumes one is working with a good printer profile. The output of this are images in sRGB and aRGB that, when printed using RelCol w/o BPC in a color managed environment will match closely the actual original, full gamut, printed image.

These digital files can be provided to someone with a need to see what the physical printed image will be should the desire to acquire it.

1. Start with the original, image in 16 bit, high gamut space. Either L*a*b* or ProPhoto preferred.

2. Convert the image colorspace using exactly the same printer settings (PerCol or RelCol, with or without BPC) the print is or was made with.

3. Make two additional duplicates. Call them ppRGB_print, sRGB_print, and aRGB_print. Close the original image.

4. Convert ppRGB_print, using RelCol w/o BPC* to ProPhoto RGB. Save the file. This is the best representation of the actual print. Particularly if there are printable colors outside sRGB and/or aRGB.

5. Convert aRGB_print, using RelCol w/o BPC* to Adobe RGB (1998). Save the file.

6. Convert sRGB_print, using RelCol w/o BPC* to sRGB. Save the file.


To see what the actual print would look like, the person with the digital files may view them with a color managed monitor or print the file ppRGB_print, using RelCol w/o BPC in a good, color managed, workflow.

When viewing with a monitor, the closest match to the print would be the aRGB_print when using a wide gamut monitor or the sRGB_print when using an unknown or sRGB like gamut. An accurate rendition of what the print would look like requires a profiled monitor at a minimum.

The usual issues of matching proofing on a monitor to print viewing is, of course, a prerequisite for monitor viewing.

[Mark D Segal]

One of the issues in editing, even in a completely color managed operation, is that the monitor rendering itself, actually uses matrix conversion with clipping -

Doug, you've made this point several times now in this thread, and I'm not sure whether it is "necessarily" correct. There are different kinds of display profiles. It depends on what software one uses to create the profile. BasicColor creates LUT profiles, not matrix. NEC Spectraview does the latter.

[Doug Gray]

Doug, you've made this point several times now in this thread, and I'm not sure whether it is "necessarily" correct. There are different kinds of display profiles. It depends on what software one uses to create the profile. BasicColor creates LUT profiles, not matrix. NEC Spectraview does the latter.

Good points. I've never used one but I've heard they exist.  In a sense they just add another dimension to the problem.  They could be better than matrix conversions or they might be worse. Ideally, a monitor profile would map out of gamut colors in a ways similar to the way printer profile makers do. Maybe they do. Wonder if someone has tested these in out of gamut applications?

[Mark D Segal]

Good points. I've never used one but I've heard they exist.  In a sense they just add another dimension to the problem.  They could be better than matrix conversions or they might be worse. Ideally, a monitor profile would map out of gamut colors in a ways similar to the way printer profile makers do. Maybe they do. Wonder if someone has tested these in out of gamut applications?

Well, actually, as far as I'm concerned there is no problem. The display provides a very satisfactory prediction under soft-proofing of what will come out of the printer, because I am properly colour-managed from start to finish - notwithstanding the differences in gamut shape and DMax between the two output of the two devices, one of which transmits light and the reflects it. Prlnter profiles that provide good soft-proofing handle this gap quite nicely.

[digitaldog]

Well, actually, as far as I'm concerned there is no problem.

Ditto, same on this end.
I'm still scratching my head what all this is about  .
I do think an old and famous Bruce Fraser quote might be appropriate:



You can do all sorts of things that are fiendishly clever, then fall
in love with them because they're fiendishly clever, while
overlooking the fact that they take a great deal more work to obtain
results that stupid people get in half the time. As someone who has
created a lot of fiendishly clever but ultimately useless techniques
in his day, I'd say this sounds like an example.


Bruce

[Doug Gray]

Ditto, same on this end.
I'm still scratching my head what all this is about  .
I do think an old and famous Bruce Fraser quote might be appropriate:



You can do all sorts of things that are fiendishly clever, then fall
in love with them because they're fiendishly clever, while
overlooking the fact that they take a great deal more work to obtain
results that stupid people get in half the time. As someone who has
created a lot of fiendishly clever but ultimately useless techniques
in his day, I'd say this sounds like an example.


Bruce

Amusing, but there is nothing here even close to fiendishly clever or really even clever. As you pointed out numerous times - similar things have been done before.  It's a form of soft proofing, or, when downloaded and printed, hard proofing.

I only looked into it because I had noticed the simplistic way matrix based RGB colorspaces converted out of target gamut colors and started wondering about how printer profiles did the same task using 3D LUTs. Knowing the approaches were radically different, I thought it interesting to see just what the differences were.

Since I'm also handy with math and computer tools it was a fun and diverting, task. Since it's orthogonal to my usual pursuits and I am under no disclosure restrictions I thought I'd share it as others may be interested.

Perhaps the thing that has most astonished me is how close sRGB images can be made to match a print that is supposedly showing off the advantages of high gamut print processing. I have yet to find an image, going from full ProPhoto RGB to printer space and back to Adobe RGB where the Adobe RGB printed image is visually different from the ProPhoto image.  High saturation sRGB images still print differently but they are significantly closer. I am starting to think much of what I had chalked up as just hitting the limits of sRGB was, in fact, due to this flawed gamut conversion.

I'm a "just the facts' kind of guy. There is way too much hand waving in printing and image work.

People that work only in the limited gamut, sRGB space, but maintain a good color managed workflow aren't giving up as much as I had previously believed.

And that's just the cold, hard, numbers.