Luminous Landscape Forum
Raw & Post Processing, Printing => Printing: Printers, Papers and Inks => Topic started by: shewhorn on December 27, 2007, 03:14:35 am
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I highly suspect one of the following things:
1) I don't understand what the gamut warning feature is supposed to be telling me and I'm attempting to use it incorrectly (operator error)
2) I'm clueless (entirely possible... the more I learn, the more I realize how clueless I really am)
3) The Gamut Warning feature has a bug.
Now before I start I'm working under the assumption that:
1) A good RA-4 printer (Durst, Chromira) properly profiled can reproduce the sRGB color space and a little bit beyond.
2) A properly profiled inkjet can easily reproduce the sRGB gamut and beyond. This is supported by my own experience of looking at the same test prints produced on a Chromira, a Durst Lamda, and an Epson 2200 (I trust the labs I got the test prints back from did a decent job with their profiles (Pechmans for the Durst and Fotoworks for the Chromira... their output is much better than a lab like WHCC which doesn't in my opinion produce very good profiles).
I wanted to create a very basic test file. I created a 2400x3000 pixel file in the sRGB color space at 8 bits (I actually started out with ProPhoto but after seeing the results I was getting I dumbed it down to sRGB). I then created 14 divisions, each with a gradient in it (the divisions were running vertically on the page). I created two sets of gradients for each color those being X to black (where X is the color) and X to white. The values I used are as follows (numbers are in the format of Red, Green, Blue)
255,0,0
0,255,0
0,0,255
255,0,255
255,255,0
0,255,255
So with two sets of that (one going to black, the other going to white) I had 12 gradient strips. I also created a white to black gradient and finally one strip that was grey (128, 128, 128).
Now here's where I got thrown for a complete and total loop. I selected Canon's Premium Matte Highest for their IPF6100 as my profile and then turned on Gamut Warning. If I'm to believe what the Gamut Warning is telling me, with a file in an sRGB color space being printed to Canon Premium Matte paper with an IPF6100, the printer can not reproduce reds above 79,0,0, greens above 0, 199 0 (there was also a gap in the middle of the green) and blues above 0,0,52. The only color it seemed to do good with was yellow which pretty much went to 255, 255, 0.
Also, if I'm to believe the Gamut Warning feature in Photoshop, for the same paper the Epson 2200 has a wider Gamut than the IPF5000 (compared canned profiles for Ilford Smooth Pearl). Now, the Epson 2200 was a great little inkjet for its day but the Lucia inks are by far superior to the first generation UltraChrome inks. I know that wider gamut does not necessarily translate to a better print but, I did not expect to see that.
So, the results I'm seeing don't reconcile with the results I'm expecting to see which is what brings me here. Set me straight folks! I've attached a screen shot of what it looks like with Gamut Warning turned on so you can get an idea of what I'm seeing.
Cheers, Joe
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Which rendering intent did you use and did you set paper white/black point compensation etc? Did you create a 16 or 8 bit image? What dimensions (in order to tell how many steps it's taking from 0-255)?
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I can pass along a couple of things I have learned.
First, gamut warning is an all or nothing kind of thing; a color that is just barely outside the gamut of your ink/printer/paper combination will be grey'd out just as much as a science fiction color far outside the gamut. So an image can be almost entirely grey'd out in Photoshop's gamut warning display, yet still print very well if most of those colors are just barely outside the gamut.
Second, matte papers with any pigment printer yield a much more restricted gamut than you'll get from any semi-gloss or luster type paper. Just use one of the utilities that provide comparative 3-d gamut plots and check out the difference between the gamut of (say) your printer's standard glossy paper and any matte you want to try. The gamut restriction imposed by matte papers can be quite dramatic.
Thirdly, there are significant gamut differences between various printers. For example, the Epsons have a wider gamut in dark reds/oranges, while the HP Z3100 has a wider gamut in lighter greens/blues. So an artificial "gamut test" like you're performing will uncover gamut limits from any printer. Exactly where will depend on the printer.
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The gamut warning overlay is legacy stuff that was kind of useful before Photoshop 5.0 and true soft proofing, its pretty useless today.
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Which rendering intent did you use and did you set paper white/black point compensation etc? Did you create a 16 or 8 bit image? What dimensions (in order to tell how many steps it's taking from 0-255)?
[a href=\"index.php?act=findpost&pid=163355\"][{POST_SNAPBACK}][/a]
They're using canned profiles... either way, as far as I know regardless of what those settings are they wouldn't explain the differences I'm seeing here (the gamut warning is supposed to display out of gamut colors for the selected soft profile compared to the source file so regardless of whether or not you're using a relative or perceptual rendering intent, it doesn't matter, if the source is out of gamut, it's out of gamut and none of those settings will make a difference.. they merely describe whether or not the rendering method used is going to truncate out of gamut data, or remap everything to be in gamut, etc.).
Cheers, Joe
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The gamut warning overlay is legacy stuff that was kind of useful before Photoshop 5.0 and true soft proofing, its pretty useless today.
[a href=\"index.php?act=findpost&pid=163363\"][{POST_SNAPBACK}][/a]
Would you please expound on that a little? Why is it useless, and what should we use instead?
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Would you please expound on that a little? Why is it useless, and what should we use instead?
[{POST_SNAPBACK}][/a] (http://index.php?act=findpost&pid=163366\")
Load the profile for the print process in Customize Proof Setup. Instead of an ugly overlay, you see the colors map into the output color space (of course, using your display gamut). Far more useful.
[a href=\"http://www.ppmag.com/reviews/200410_rodneycm.pdf]http://www.ppmag.com/reviews/200410_rodneycm.pdf[/url]
http://www.ppmag.com/reviews/200411_rodneycm.pdf (http://www.ppmag.com/reviews/200411_rodneycm.pdf)
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Would you please expound on that a little? Why is it useless, and what should we use instead?
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In the Camera to print tutorial it was mentioned that it was there before soft proofing became known, and is no longer valid,per se, when soft proofing. Using it will indicate out of gamut color, but not by how much. Michael indicated that he used it to see which specific areas he needed to work on as far as out of gamut color was concerned. Jeff just rolled his eyes..
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Have to run out to meet a client... be back in a bit to respond to the rest of the posts. Thanks for now though. Be back later.
Cheers, Joe
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The gamut warning overlay is legacy stuff that was kind of useful before Photoshop 5.0 and true soft proofing, its pretty useless today.
[a href=\"index.php?act=findpost&pid=163363\"][{POST_SNAPBACK}][/a]
I think there is still a place for the gamut warning, since soft proofing is limited by the gamut of our monitors. Most monitors approximate the gamut of sRGB and a few the gamut of aRGB, but ProPhotoRGB is the recommended working space and many of our better inkjet printers easily exceed the gamut of aRGB. What we need to know is not only is a color out of gamut, but by what amount. Currently one must use gamut mapping software such as ColorThink or GamutVision for this task.
For example, here is a picture of a saturated red flower in ProPhotoRGB with a lot of out of gamut colors in aRGB, sRGB, and the printer space. The printer out of gamut amount (in terms of ΔC CMC, which takes color but not luminance into account) is shown by Gamutvision:
(http://bjanes.smugmug.com/photos/236433252-O.png)
And by Photoshop's out of gamut display (yes, one should use 16bpc with ProPhoto, but this is for demonstration only):
(http://bjanes.smugmug.com/photos/236433263-O.png)
If one prints this image with relative colorimetric rendering, much of the flower is a red blob with no texture. Softproofing is limited by the monitor, which can not display the full gamut of the printer. One can use perceptual rendering (which most admit is brain dead) or edit the image to bring the red saturation down a bit so that some texture appears in the flower.
Bill
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I think there is still a place for the gamut warning, since soft proofing is limited by the gamut of our monitors.
[a href=\"index.php?act=findpost&pid=163378\"][{POST_SNAPBACK}][/a]
If you can't see it on your monitor, what can you see it on? The print. Print it out. Use the soft proof to help you pick a rendering intent and decide if you wish to edit (a copy) of the image further based on the soft proof and original image in your working space (which I would submit is out of display gamut too).
If you find the overlay useful, great. Just keep in mind when it was invented and for what based on the current technology then consider what we have today. For most users, the feature could go away (and probably should but Adobe hates to ever remove anything despite nearly everyone agreeing its too complicated).
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Load the profile for the print process in Customize Proof Setup. Instead of an ugly overlay, you see the colors map into the output color space (of course, using your display gamut). Far more useful.[a href=\"index.php?act=findpost&pid=163369\"][{POST_SNAPBACK}][/a]
I do this already. What it doesn't tell me is where I'm going out of gamut.
This brings up another point. Might be obvious to everyone but me, but here goes anyway. It seems to me that one would want to print with everything in gamut. That is, set up soft proofing, find out what is out of gamut, decide the best way to bring it in gamut, then make the appropriate adjustment(s) as required. Then print.
But from the sounds of this conversation, it sounds like many people print with some colors out of gamut. What would be the advantage of printing out of gamut colors? Since they can't print as sent to the printer they have to be clipped by whatever method (rendering intent) the printer/profile are programmed to use.
Instead of printing out of gamut images and letting the rendering intent and profile decide how to clip the image and rearrange your colors, doesn't it make since to pull everything in gamut first before printing? Sorry to be dull, but what am I missing here?
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The profiles in large part do the heavy lifting here with gamut mapping. If its out, its out. Now what do you do? Do you clip all colors to the boundary of the new color space or alter all colors in a relationship which is very specific to how the manufacturer of the profile builds this mapping. You can see significant differences in three custom profiles to the same device, built from three different packages when you examine the Perceptual matching even in the soft proof.
We're dealing with, in this case, an ultimate output. A print. It has a specific gamut, one that exceeds what we can see on our displays in some areas. At some point, you've got to take the colors you have and map them to the colors of your output device. That's the only time you'll see them.
We're also dealing with two vastly different output mediums (reflective and emissive).
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I've posted this question to another forum as well and one of my friends asked an obvious question with regards to what the prints look like. My interest initially wasn't really in how the gamut warning applies to prints (I've usually relied upon soft proofing and a hard proof when I'm unsure), rather it was merely academic but, the question prompted me to print out these silly color bars to see what would happen. The results were extremely educational to say the least and I think the response I posted is worth posting here as well so here goes....
My curiosity is merely academic at this point. Gamut warning is not a feature I really use all too often (I just soft proof, if I'm loosing detail due to an oversaturated color I can usually spot the offending egregious loss of detail) but I do occasionally use it for another point of information.
Anyhow when you said "printed image" I figured... what the heck, I'll print out these stupid bars and see what happens. I created a new file, 16 bits, ProPhoto color space, same configuration as above. The first file was uncorrected... just printed it straight out. With the 2nd file I selected the proper profile for soft proofing (in this case I used a relative colorimetric rendering intent), enabled the gamut warning, and then used a hue saturation layer and eyedrop selecting each bar and kicking down the saturation to bring them into gamut.
I printed to Canon Photo Paper Plus (it's a glossy paper, gamut is not as good as something like Hahnemuhle Photo Rag Pearl but... I don't have any more of that paper and it's a bit expensive to be doing this kind of testing on (at least until I have a clear goal in mind)... I hate glossy papers thus any excuse I can find to... ahhh you get the idea) using Canon's 16 bit driver (which is really 12 bits) set to unidirectional printing at the highest quality (16 pass).
The results were extremely interesting to say the least. I'm still trying to process what I'm seeing, I think it will take me a while to mull it over and make sense of it. A few quick observations... Blue gradient fading to black starting at 0,0,255. It may as well have been a big black bar and I'm not exaggerating all that much. The equivalent on screen seems to be about 0,0,22. It is THAT dark. The blue fading to white was also interesting. It starts out at the top (which should be 0,0,255) at what appears to be the equivalent on my screen to 0,0,22, fades to a bright blue (at which the point on screen measures at about 62, 62, 255). So, bright blues would appear to be limited with this paper (I'd be curious to see a 3D plot of that in ColorThink... which I need to buy). On the "corrected" print, the blues looked MUCH better, not bright but they definitely appeared to have more of a tonal range. I'm still not quite sure what to make of this, there's a few things that don't sit well with me but I need to sleep on it to figure out just how to precisely convey the "what" part.
Aside from the blues I can't say that one was clearly better than the other. I'm leaning towards saying that the colors on the corrected print were more accurate but that accuracy came at a rather high cost. Yellows and reds even though the gamut warning indicating things were out of range looked much better on the uncorrected version as they were far more vibrant. I wouldn't want to desaturate any print to the extent with which I had to do so in order to bring those colors "in line". The blues CLEARLY benefited in the corrected file, no doubt about that. Greens... I'd say the corrected version was slightly more accurate (the uncorrected had a slight shift towards yellow towards the top end of things). There's a bunch of other observations as well but I could ramble on quite a bit. Bottom line is, neither print was optimal.
Another thought on the blues... desaturating the blues on screen was as far as my perception is concerned, equivalent to ADDING saturation to the final print. Very counter intuitive (this is one of the things I'm grappling with... the engineering brain wants to know what's going on with the numbers to cause such an effect).
Now... using a perceptual rendering intent things were far more accurate however, the relative colorimetric print with the corrected blues definitely won in the blue department. In the real world however I've found that the perceptual rendering intent screws around with my colors a bit too much because of what it's doing.
I'm just scratching the surface here with everything this little test has taught me (I also learned some interesting things about the ProPhoto color space). Fortunately most things in nature aren't as vibrant as the ProPhoto color space or even Adobe RGB... well at least wedding subject matter, fall foliage might be a different story. UNfortnautely there is one color that appears in nature quite a bit... deep blues right after sunset. Of course... I love that time of day and tend to like to take it to a surreal level and love to saturate the CRAP out of it which makes for an interesting challenge.
Anyhow... I still have a lot more to chew on.
Cheers, Joe
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I have certainly found the gamut warning useful and use it to make localised saturation adjustments (not global adjustments). Open fires and lit candles in interior shots are what springs to mind. If I don't bring the reds/oranges down they will print green and it's just a wasted print.
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From the tests I did today I'm starting to form an opinion which is a mix of what I'm reading here and that is, the gamut warning feature isn't entirely useless but on the same token, it's an extremely imprecise tool for making judgments about correcting such flaws and it is more likely than not to lead you astray.
Wish I could remember the details, I caught the tail end of one of John Paul Caponigro's lecture at Photoshop World in Boston and he didn't seem to be a huge fan of the gamut warning tool either. He had another (more accurate) technique for soft proofing out of gamut colors but I can't for the life of me remember what it was. I'll have to dig up the notebook to see if it's in there.
Cheers, Joe
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Wish I could remember the details, I caught the tail end of one of John Paul Caponigro's lecture at Photoshop World in Boston and he didn't seem to be a huge fan of the gamut warning tool either. He had another (more accurate) technique for soft proofing out of gamut colors but I can't for the life of me remember what it was. I'll have to dig up the notebook to see if it's in there.
Cheers, Joe
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Hint, I bet it required the use of a gradient.
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Hint, I bet it required the use of a gradient.
[a href=\"index.php?act=findpost&pid=163429\"][{POST_SNAPBACK}][/a]
Andrew, you coy fellow, share with rest of us! ;-)
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Hint, I bet it required the use of a gradient.
[a href=\"index.php?act=findpost&pid=163429\"][{POST_SNAPBACK}][/a]
Ahh... interesting (do share) BUT... I'm pretty sure he wasn't using and gradients. I seem to remember using the Hue/Sat filter, perhaps as a layer in a certain blend mode. By enabling soft proofing and observing what would happen when you tweaked the saturation slider you could more readily identify colors that were going to be a real problem in print.
I'll have to dig.
Cheers, Joe
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Ahh... interesting (do share) BUT... I'm pretty sure he wasn't using and gradients.
[{POST_SNAPBACK}][/a] (http://index.php?act=findpost&pid=163436\")
...and I'm POSITIVE he WAS using gradients...it's called "Bracket Proofing" where he uses a gradient on an adjustment layer where the adjustment goes from WAY too strong to too weak. You choose the location in the gradient that gives you the optimal results and then fill the gradient with the level of tone to achieve that level of adjustment. He has a PDF available for free at [a href=\"http://www.johnpaulcaponigro.com/lib/downloads/index.php#]Downloads[/url] look for the Bracket Proofing in the "Technique" section.
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If you can't see it on your monitor, what can you see it on? The print. Print it out. Use the soft proof to help you pick a rendering intent and decide if you wish to edit (a copy) of the image further based on the soft proof and original image in your working space (which I would submit is out of display gamut too).
[a href=\"index.php?act=findpost&pid=163382\"][{POST_SNAPBACK}][/a]
Yes, but does that not at least partially obviate the purpose of soft-proofing in the first place? And do you wish to make another print for each rendering intent and saturation edit whose effect you can't see on the monitor? Until our monitors match the gamut of the final output, there will be some problems with soft proofing.
If you find the overlay useful, great. Just keep in mind when it was invented and for what based on the current technology then consider what we have today. For most users, the feature could go away (and probably should but Adobe hates to ever remove anything despite nearly everyone agreeing its too complicated).
[a href=\"index.php?act=findpost&pid=163382\"][{POST_SNAPBACK}][/a]
The current PS overlay is not particularly useful, but one with a delta C such as I demonstrated would give some useful information, particularly if available real time and when used with rendering intents or saturation edits. Why soft proof it it still takes multiple print iterations? Better tools could cut down the number of test prints necessary to get the fullest gamut possible from the printer. Perhaps you can do it all with one test print, but others may not be so fortunate.
Bill
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Yes, but does that not at least partially obviate the purpose of soft-proofing in the first place?
[a href=\"index.php?act=findpost&pid=163448\"][{POST_SNAPBACK}][/a]
Not unless you were under the impression that a soft proof perfectly matches the final which so far, no one should be saying.
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...and I'm POSITIVE he WAS using gradients...it's called "Bracket Proofing" where he uses a gradient on an adjustment layer where the adjustment goes from WAY too strong to too weak. You choose the location in the gradient that gives you the optimal results and then fill the gradient with the level of tone to achieve that level of adjustment. He has a PDF available for free at Downloads (http://www.johnpaulcaponigro.com/lib/downloads/index.php#) look for the Bracket Proofing in the "Technique" section.
[a href=\"index.php?act=findpost&pid=163443\"][{POST_SNAPBACK}][/a]
Yes, but how is the bracket proof evaluated? With current soft proofing (where the result might not be visible on the screen) or with the useless gamut indicator?
Bill
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Not unless you were under the impression that a soft proof perfectly matches the final which so far, no one should be saying.
[a href=\"index.php?act=findpost&pid=163449\"][{POST_SNAPBACK}][/a]
From my original post, I was obviously aware that the soft proof is limited by the gamut of the screen, so I find your reply superfluous, except that it enables you to get in the last word as is your wont. If colors in the image are far out of gamut, I might want to make some adjustments before wasting time and paper.
Bill
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Yes, but how is the bracket proof evaluated? With current soft proofing (where the result might not be visible on the screen) or with the useless gamut indicator?
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Either soft proofing or print proof, or both...
Obviously, from the name "soft proof" nobody should be expecting a 100% accurate replication of the final print. DOH...and nobody I know expects that. What soft proofing DOES do is allow a gamut and dynamic range prediction of the print and, when used correctly, allows one to get a _LOT_ closer to what the final print will look like without ink hitting paper.
And, while it's not 100% accurate, I would say it's close to about 85-90% accurate prediction which is STILL more useful that looking at the image in its native color space on a display without soft proofing. Right? And soft proofing is more useful that merely looking at the gamut warning to see what's out of gamut.
So, while it ain't perfect, it's better than nothing and more efficient in time & costs to soft proof prior to printing than printing a ring-a-round and twiddling with images AFTER making a bunch of prints.
Do you actually soft proof? Do you print? Is it not useful to you? If not, I would suggest learning how to soft proof and determine for yourself its usefulness in your own work. Arguing about the limitations of display gamuts won't get a print done better/faster, will it?
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Either soft proofing or print proof, or both...
Obviously, from the name "soft proof" nobody should be expecting a 100% accurate replication of the final print. DOH...and nobody I know expects that. What soft proofing DOES do is allow a gamut and dynamic range prediction of the print and, when used correctly, allows one to get a _LOT_ closer to what the final print will look like without ink hitting paper.
And, while it's not 100% accurate, I would say it's close to about 85-90% accurate prediction which is STILL more useful that looking at the image in its native color space on a display without soft proofing. Right? And soft proofing is more useful that merely looking at the gamut warning to see what's out of gamut.
So, while it ain't perfect, it's better than nothing and more efficient in time & costs to soft proof prior to printing than printing a ring-a-round and twiddling with images AFTER making a bunch of prints.
Do you actually soft proof? Do you print? Is it not useful to you? If not, I would suggest learning how to soft proof and determine for yourself its usefulness in your own work. Arguing about the limitations of display gamuts won't get a print done better/faster, will it?
[a href=\"index.php?act=findpost&pid=163455\"][{POST_SNAPBACK}][/a]
Of course, I print and I also soft proof. Why do you always assume that anyone other than your and your gang are ignorant? If you had taken the trouble to view my post, you would have seen a soft proofing screen. As it was, you made unjustified implications.
BTW, I purchased and have viewed carefully the From Camera to Print video by you and Michael, so I can't be completely ignorant, or else you are a poor teacher . IMHO, gamut mapping software is a valuable addition to soft proofing, at least if you know how to interpret the output. Do you? I am not arguing about the limitations of display gamuts, but am simply pointing out a different way to view by what extent a color may be out of gamut, something that the OP or one of the follow on posters inquired about.
Bill
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Of course, I print and I also soft proof.
[a href=\"index.php?act=findpost&pid=163461\"][{POST_SNAPBACK}][/a]
From your posts and the fact you were bemoaning the inability of displays to approach the gamut of prints, I couldn't tell. Sounded like you were arguing the technicalities without the benefit of experience...
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Post withdrawn by poster.
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From your posts and the fact you were bemoaning the inability of displays to approach the gamut of prints, I couldn't tell. Sounded like you were arguing the technicalities without the benefit of experience...
[a href=\"index.php?act=findpost&pid=163481\"][{POST_SNAPBACK}][/a]
Really? That is your uncharitable and biased take. Typical bull in a china closet, lacking in any subtlety or nuance. Sometimes, it is better to actually read and try to understand what others are saying, rather than jumping to unjustified conclusions from your narrow point of view.
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Really? That is your uncharitable and biased take. Typical bull in a china closet, lacking in any subtlety or nuance. Sometimes, it is better to actually read and try to understand what others are saying, rather than jumping to unjustified conclusions from your narrow point of view.
[a href=\"index.php?act=findpost&pid=163491\"][{POST_SNAPBACK}][/a]
Oh, for heavens sake. Go get some sleep. David
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He has a PDF available for free at Downloads (http://www.johnpaulcaponigro.com/lib/downloads/index.php#) look for the Bracket Proofing in the "Technique" section.
[a href=\"index.php?act=findpost&pid=163443\"][{POST_SNAPBACK}][/a]
Well I guess that settles that then. If only I could upgrade MY OWN memory.
Cheers, Joe
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I wanted to create a very basic test file. I created a 2400x3000 pixel file in the sRGB color space at 8 bits (I actually started out with ProPhoto but after seeing the results I was getting I dumbed it down to sRGB). I then created 14 divisions, each with a gradient in it (the divisions were running vertically on the page). I created two sets of gradients for each color those being X to black (where X is the color) and X to white. The values I used are as follows (numbers are in the format of Red, Green, Blue)
255,0,0
0,255,0
0,0,255
255,0,255
255,255,0
0,255,255
So with two sets of that (one going to black, the other going to white) I had 12 gradient strips. I also created a white to black gradient and finally one strip that was grey (128, 128, 128).
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Joe,
I made my own testimage and got somewhat different results with the gamut warning as shown below for perceptual rendering with the Canon Matte Profile which I downloaded from the Canon USA site. The map is not useful because it does not indicate if the color error is large or small:
(http://bjanes.smugmug.com/photos/237475747-O.png)
The standard way to express a color error is with ΔE (which measures both luminance and chrominance in the 3 dimensional relatively perceptually uniform L*a*b space. Some workers prefer ΔC which ignores luminance and takes only color into account). There are several varieties of these measurements, but I am using *CMC. One loads the image in to Gamutvision and a soft proof is given on the upper right. ΔE or ΔC magnitudes are shown by a pseudo color display with the key on the right. Note that the ΔE on the top has a gamut problem because of with low luminance in the shadows. This does not show on the ΔC plot or on the Photoshop Gamut display, but it should show up with softproofing with black point compensation turned on.
(http://bjanes.smugmug.com/photos/237475684-O.png)
(http://bjanes.smugmug.com/photos/237475680-O.png)
Correlation between the Gamutvison result and PS is not that good.
The whole test is not that useful because the sRGB color space contains colors that can't be printed and there are many colors that the printer can handle, but are out of the sRGB gamut.
The 3D plot below demonstrates the sRGB (the wireframe) contains high luminance greens and a few yellows that can't be printed, and that some yellows and oranges at high luminance are in gamut for sRGB and out of the printer gamut. By contrast, at lower luminance there are greens, blues, and cyans that are out of sRGB but well within the printer gamut. There is no rendering in these views, which only show the two gamuts. The wire frame is sRGB and the solid color represents the printer space.
(http://bjanes.smugmug.com/photos/237475715-O.png)
Here is what happens with perceptual rendering. The wire frame is the ouput (printer) space and the vectors show how the rendering affects low luminance values (the matte paper does not have deep blacks) and high luminance saturated primaries. There are a great many out of gamut colors, which are clipped by the relative colorimetric rendering. Perceptual rendering can not handle such large out of gamut conditions, and the results are similar.
(http://bjanes.smugmug.com/photos/237903278-O.png)
Research at Kodak and elsewhere has shown a gamut of colors which represent real work surface colors which actually appear in photographs. Excluded are highly saturated self-luminous or florescent objects, neon lights, and computer generated display. Here is a saturation plot demonstrating the real world surface colors along with the gamuts of ProPhotoRGB, aRGB, and sRGB drawn up by Prof. Dr Gernot Hoffman in Germany. The dotted line shows the gamut of the surface colors, and the gamuts of three common spaces are also shown. ProPhotoRGB covers the whole surface gamut, but the smaller spaces do not.
(http://bjanes.smugmug.com/photos/237613131-O.png)
These are 2 dimensional plots showing mid luminances that are most important. At high and low luminances, even sRGB has some colors which can not be printed, but these are not real world colors and are not important. This is shown in this Kodak paper on Color.org. Download and view at your convenience.
[a href=\"http://www.colour.org/tc8-05/MetricsUpdateNov01.pdf]http://www.colour.org/tc8-05/MetricsUpdateNov01.pdf[/url]
Note how the Canon printer colors include important greens at mid luminance that are well outside the sRGB gamut shown by most monitors and not fully in gamut for aRGB. This eplains why ProPhotoRGB is the preferred working color space for digigal photography with modern inkjet printers. Glossy papers have an even better gamut. Softproofing might be problematic with these colors. Herr Schewe can indicate how he handles them.
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[a href=\"index.php?act=findpost&pid=164118\"][{POST_SNAPBACK}][/a]
bjanes,
Your contributions are very much appreciated.
DPL
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bjanes,
Your contributions are very much appreciated.
DPL
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[a href=\"index.php?act=findpost&pid=164175\"][{POST_SNAPBACK}][/a]
Thanks for the kind words, DPL. I think that my post did clear up some of the OPs concerns, but neither he nor anyone else has responded. Disappointing.
Bill
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There is a read out mode option in the Info Palette for Proof Color. The first read out can be selected for Actual Color, and the second read out for Proof Color (rgb in italic). At any given sample point, the two read out values are different, regardless of whether I'm in Soft Proof or not.
Questions:
- What is the definition of Proof Color?
- How can we make use of this information?
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- What is the definition of Proof Color?
- How can we make use of this information?
[a href=\"index.php?act=findpost&pid=164549\"][{POST_SNAPBACK}][/a]
The info palette can read out what the actual color WILL be based on the proof set up. However, it's not particularly useful when printing RGB to drivers that want RGB unless certain RGB readouts may mean something to you. It's primarily designed to be used with RGB images and CMYK output (or CMYK files being cross-rendered in a different CMYK space) where certain CMYK numbers may be needed and useful.
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There is a read out mode option in the Info Palette for Proof Color. The first read out can be selected for Actual Color, and the second read out for Proof Color (rgb in italic). At any given sample point, the two read out values are different, regardless of whether I'm in Soft Proof or not.
Questions:
- What is the definition of Proof Color?
- How can we make use of this information?
[a href=\"index.php?act=findpost&pid=164549\"][{POST_SNAPBACK}][/a]
The first readout is that of the color in the working color space. The second readout is that of the data that will be sent to the printer in terms of the printer color space. This can be verified by converting the image to the printer color space, giving the actual colors that will be sent to the printer. In this case, the two readouts are exactly the same.
Since printers are highly non-linear, the color that will be produced in the print (output color) is not easily predicted from the input RGB values. I don't really know of what use such data might be. What would be of interest would be the output in terms of a device independent space, such as L*a*b. You could compare with the original data, also in L*a*b, and determine the Delta E.
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bjanes...
Thanks for putting the time into your excellent response!
Cheers, Joe