Luminous Landscape Forum
Raw & Post Processing, Printing => Digital Image Processing => Topic started by: Robert Ardill on June 25, 2014, 08:32:09 am
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Following on from my (no doubt irritating) questions about out-of-gamut processing, I would appreciate your advice on soft-proofing.
First of all, I think that the most important aspect of soft-proofing is to help avoid OOG problems.
But ... I think it can also useful to be able to give an idea of what the print will look like, given the paper color, black point etc., using different rendering intents (well, Perceptual and Relative Colorimetric for us photographers).
There seem to be two schools of thought here, as far as I can make out.
The first seems to say that we should only use Black Point Compensation and Simulate Black Ink, leaving Simulate Paper Color out: the reason being, I think, that Simulate Paper Color in Photoshop only simulates D50 and doesn't match even 5000K viewing booths (can't say if this is true as I don't have a 5000K viewing booth :)). So this school of thought presumably doesn't believe in trying to match the monitor to the print.
The second seems to think that it is possible to match monitor to print, but for this it's necessary to use an expensive high-quality 5000K viewing booth with brightness controls etc (I almost bought one and feel relieved that I didn't :)).
I think the following (and as I'm not at all sure I'm right, I would very much appreciate your views):
- First of all, I think that most of the image processing should be done at 6500K and luminance of around 80cd/m2 with a wide-gamut monitor, if possible, with fairly subdued lighting in the room (or up the brightness to 100 or 120 if the light in the room is fairly bright).
- Then, before printing, view the image with Simulate Paper Color on, with the monitor image side-by-side with the illuminated paper that the image will be printed on
- Keeping the paper in the field of view, make any final adjustments before printing.
The reason (as far as I understand) why it's necessary to have the paper viewed alongside the monitor, is that the eye adjusts to the paper white automatically, whereas it doesn't to the monitor white. Having the paper white beside the monitor fools the eye into adjusting to the monitor white.
The problem with this set-up is that it will only work if the lighting is bang-on D50 (which is impossible, I would think). I use a Solux lamp which has a very good CRI and very little UV: however, this lamp is quite a bit warmer that 5000K (it's rated at 4700K, but in reality the bulb I have is closer to 4200K). So my paper will look quite a bit warmer than the monitor white (with Simulate Paper color on).
As far as I can see there are four 'solutions' to this:
- Don't do it :)
- Use an expensive viewing booth and put up with the smallish differences between monitor and print
- Change your monitor white to match the paper white (interestingly, this is a method that Eizo promotes, so it can't be such a bad idea)
- Change the profile white to match the paper white
The last option seems insane, but I think it may be the best option. I stumbled on it using ArgyllCMS as this software has an option to measure the paper white. What it does with it is to put it into the 'wtpt' tag in the icc profile. From what I’ve read in color.org and other places (for example http://www.normankoren.com/color_management_2.html) this tag is only used for Absolute Colorimetric. Certainly, changing it to anything you want (I use IccXML) makes no difference to Relative and Perceptual.
However … Photoshop does use it (and so does Lightroom) to get the paper white in Simulate Paper White. That’s pretty crazy because some profiles use D50 as the white point and others use D65, but no doubt Adobe has its reasons.
Anyway, what this means is that the white point can easily be changed to the paper white for the viewing conditions. What I do is to set up my Solux lamp to shine on a sheet of print paper beside my monitor and either get the paper white values manually (by using Lab in Photoshop to match the screen white to the paper white) or get them by using an i1Pro to measure the reflected paper white. I don't touch my monitor settings - 6500K, 80cd/m2, native gamut etc.
I then put the XYZ values into the wtpt tag … and the monitor white now matches the paper white with Simulate Paper on. But as I mentioned, it is necessary to have the illuminated paper beside the monitor when viewing the monitor image.
Exactly the same method can be used for different lighting. So if we know that a customer is using Philips D65 fluorescents, then we can either set the ‘wtpt’ tag to 6500K, or go out and buy the same tube and get a correct value for the paper we will be using.
The method does seem to work in that prints very closely match the soft-proofed image on the monitor. Here are a couple of examples:
(http://irelandupclose.com/customer/LL/Solux-setup-4.jpg)
and this shows that my set-up is somewhat work-in-progress :) ... and not entirely fire-proof!
(http://irelandupclose.com/customer/LL/Solux-setup-3.jpg)
So, I guess my question is not whether this works or not, because I know it does … but it’s whether it’s a really bad idea to do this (a bit like it may be a really bad idea to try to tweak OOG colors back into gamut using Hue/Saturation ;D). And also, are there any technical reasons why this should not be done?
If you've got this far, thanks for your patience!
Robert
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Following on from my (no doubt irritating) questions about out-of-gamut processing, I would appreciate your advice on soft-proofing.
First of all, I think that the most important aspect of soft-proofing is to help avoid OOG problems.
I don't. It's to show me what the RGB numbers will look like on a print, a simulation of what the image will translate to on paper, not the display. OOG colors are a fact of life. And not one that's really a huge issue in most cases. Having an idea what a print will look like before you print it, a soft not hard print, helps avoid wasted media, time and money. Otherwise, simply forget soft proofing (it's far from prefect but far better than nothing), just make a test print or test strip.
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Having an idea what a print will look like before you print it, a soft not hard print, helps avoid wasted media, time and money. Otherwise, simply forget soft proofing (it's far from prefect but far better than nothing), just make a test print or test strip.
Well, of course, Andrew, that's the whole reason I'm interested in soft-proofing ... not to have to waste time and money with repeated prints to get the print right (whether this is due to OOG problems or to white point or black point problems, or whatever).
But I'm not so sure I agree with you that it's far from perfect ... it isn't all the way there, but if you get the white balance and lighting right, and with good color management throughout, it's very close indeed, especially now with wide-gamut monitors.
What I meant about the OOG issue is that initially it's the important thing: soft-proofing helps to avoid what can be a major issue when you go from a very wide working space to a much narrower and less uniform destination space. Once you have that beast tamed, then soft-proofing, as a very good simulation, should come into its own to get you the print you are aiming for.
What I'm not sure about is this: if you are working at 6500K you have the gray-balance right and you should be able to adjust the image optimally; if you then move to a different white point this no longer applies (I presume); then there's the issue of the print being viewed in mostly unpredictable lighting conditions. If we know exactly what lighting will be used then soft-proofing with that precise lighting should be really good ... but mostly we don't.
So what's the answer?
I don't know. I usually try to find out from my customers what lighting they use or are likely to use and I aim for that. On the other hand there's the eye's ability to adapt to different illuminants and paper colors, so it's not so straightforward :(.
Robert
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What I'm not sure about is this: if you are working at 6500K you have the gray-balance right and you should be able to adjust the image optimally; if you then move to a different white point this no longer applies (I presume); then there's the issue of the print being viewed in mostly unpredictable lighting conditions. If we know exactly what lighting will be used then soft-proofing with that precise lighting should be really good ... but mostly we don't.
So what's the answer?
Set the soft proof to show paper white simulation first of all. Calibrate the display with that in mind (the WP of the display that results in a visual match of the print next to the display).
More than one paper that would produce more than one WP calibration? Enter something like SpectraView which allows multiple display calibration aim points and loads the associated display profile on the fly.
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Set the soft proof to show paper white simulation first of all. Calibrate the display with that in mind (the WP of the display that results in a visual match of the print next to the display).
I entirely agree that the display and paper whites should be matched side by side - otherwise the eye will not adapt to the display white. However I think it's better to alter the paper profile white point, as I tried to explain above, for two reasons: a) it's simpler, b) soft-proofing then automatically gets the correct white point without having to change anything on the monitor (or anywhere else).
More than one paper that would produce more than one WP calibration? Enter something like SpectraView which allows multiple display calibration aim points and loads the associated display profile on the fly.
I was really talking about more than one illuminant, rather than more than one paper. It's fine getting soft-proofing for a particular paper with a particular illuminant (say Canson Platine with Solux 4700K lamp) ... but a print made like this may not look so good under a fluorescent with spikes all over the place. Papers with optical brighteners are even worse (unfortunately for me I have to use one for some of my prints).
Again, there's no reason why one shouldn't have a different profile with different white points for each of these lighting conditions - it just gets to be a pain. In general I do try to find out from my customers what sort of lighting they have ... but apart from galleries the best most of them can say is that 'I have neon tubes in the ceiling' or something like that :).
Robert
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I actually find Soft Proofing useful even though I don't print on fine art 100% rag non-glossy paper, just 8x10's off my $50 Epson All In One using Epson's Ultra Premium Glossy.
But I don't implement it the same as others since I print using "Printer Manages Color". What I do is download one of Epson's wide format 7800 series printer profiles of similar paper and check my saturation levels by noticing any luminance hits with Relative Intent setting. That's my OOG "posterized" warning sign instead of relying on Photoshop's OOG.
I then print a small strip of the area in question as Andrew suggests. Most of the time even with a luminance hit Soft Proofing this way my Epson still prints the OOG portions as it appears on screen. Most of the time it's hue shifts, not flat blobs of blown detail I have to correct for which I use ACR's HSL panel to fix. I don't like using any of Photoshop's color editing tools when I have something more easier and immediate with the least noise induced artifacts using the HSL panel in the Raw converter.
Nice setup by the way. Just hope your Solux lamp's power converter doesn't crap out like it did on mine.
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What I'm not sure about is this: if you are working at 6500K you have the gray-balance right and you should be able to adjust the image optimally; if you then move to a different white point this no longer applies (I presume); then there's the issue of the print being viewed in mostly unpredictable lighting conditions. If we know exactly what lighting will be used then soft-proofing with that precise lighting should be really good ... but mostly we don't.
So what's the answer?
I don't know. I usually try to find out from my customers what lighting they use or are likely to use and I aim for that. On the other hand there's the eye's ability to adapt to different illuminants and paper colors, so it's not so straightforward :(.
Robert
I won't be a customer of yours for obvious reasons but the thread I started...
http://www.luminous-landscape.com/forum/index.php?topic=89689.0
...was my answer to my lighting situation for my own personal prints and may answer some your questions you have about how your customers are going to be viewing your prints. Expect the worse is all I can say but I'ld suggest you tell them they'll need a full spectrum light similar to the Solux to see the same results at point of purchase online and in your studio.
Regarding that link to my print lighting dilemma the orange flower was OOG for my Epson and was rendering it with too much magenta so I had to make it far too yellowish to compensate. Soft Proofing using the Epson 7800 series profile (assuming it has a much wider color gamut) didn't show this hue shift which I think most Soft Proofing won't according to what I've seen of its use even with custom printer profiles in these forums, but I can't be sure.
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I'll explain the steps I take in detail to soft-proof. I would be very interested if one of you would try this out.
- With the illuminated paper white beside the monitor, I create a new document in Photoshop and (in full-screen mode) I adjust the Lab values so that I get a visual match to the paper white.
- I convert these Lab values to XYZ using http://www.brucelindbloom.com/index.html?WorkingSpaceInfo.html (http://www.brucelindbloom.com/index.html?WorkingSpaceInfo.htmlhttp://). The Ref. White must be D50. This gives me the XYZ values for the paper white.
- I convert the paper profile to xml using IccXML: http://sourceforge.net/projects/iccxml/ (http://sourceforge.net/projects/iccxml/)
- I copy and paste the XYZ values from Bruce Lindbloom's calculator into the 'wtpt' tag in the xml version of the paper profile
- I convert the xml version of the profile back to icc, again using IccXML
- The modified profile can now be used to soft-proof: Simulate Paper will give the correct paper white for the lighting conditions used.
It would be relatively easy to write a program to automate this process - but even manually it only takes a few minutes.
I don't really understand what Photoshop is doing, to be honest. Perhaps someone does? My guess is that it does something like this for softproofing:
- First of all, it converts the image to the destination profile and back again. This adjusts the OOG colors, black point etc.
- Then it re-maps the image to the white point in the 'wtpt' tag using ... the Bradford transform, perhaps?? http://en.wikipedia.org/wiki/White_point (http://en.wikipedia.org/wiki/White_point)
Be interesting to know.
Robert
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I'ld rather print than go through all that trouble, Robert.
I paid for the technology to do its job which is pretty decent considering the level of complexity working under the hood and accept its limits and move on.
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I'ld rather print than go through all that trouble, Robert.
I paid for the technology to do its job which is pretty decent considering the level of complexity working under the hood and accept its limits and move on.
Well, the thing is, Tim, that this IS using the technology (or at least attempting to :)). However ... I accept that setting up a color-managed workflow to that extent won't float everyone's boat. But for those who want to fine-tune things so that what you see is what you get (or as close as possible) ... well, then, as a minimum, you do have to calibrate and profile your monitor and printer.
I think you are using a profile made for one printer to give you an idea of OOG problems on another printer ... well, that will probably sort of work. Then I assume you're printing using sRGB with the printer managing the color - which is fine. But if you want to make the best of your printer then you would need to profile it for its full gamut and not restrict it to sRGB. Still, if you're happy with the way you're doing things then that's great!
Robert
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- With the illuminated paper white beside the monitor, I create a new document in Photoshop and (in full-screen mode) I adjust the Lab values so that I get a visual match to the paper white.
And I do this building the display profile (SpectraView allows me to produce visually that white, builds all that into the calibration and profile).
I copy and paste the XYZ values from Bruce Lindbloom's calculator into the 'wtpt' tag in the xml version of the paper profile
And this updates the AtoB, BtoA or both tabes? I'm not sure this is a good route to go down but I need a lot more coffee and some time to think about it. I'm thinking this should be done on the preview/display side, not in the output profile but again, what tables are affected is kind of critical here.
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And I do this building the display profile (SpectraView allows me to produce visually that white, builds all that into the calibration and profile). And this updates the
Yes, that's an alternative way of doing it. ColorNavigator from Eizo also has a very nice feature to allow visual adjustment of the monitor profile to match the print white. Here is their recommendation: http://www.eizo.com/global/library/management/matching/ (http://www.eizo.com/global/library/management/matching/).
It's a bit more awkward to use (with the Eizo at any rate) because there is a need to switch profile when soft-proofing. It's only a click of a button, but still. If you modify the print profile you can use softproofing with or without Simulate Paper Color, but when you click on Simulate Paper Color you get the right white without having to do anything at all. So you can stay at 6500K all the way through. All I can say is that it works really well ... you should give it a go, it's not hard to do.
I don't know to what extent this matters, but generally the recommendation for LCDs is to stay at 6500K and not go down to 5000K or below (quite a bit below with a Solux lamp) because of possible banding issues.
AtoB, BtoA or both tabes? I'm not sure this is a good route to go down but I need a lot more coffee and some time to think about it. I'm thinking this should be done on the preview/display side, not in the output profile but again, what tables are affected is kind of critical here.
Well the only change is to the wtpt tag. However ... I have no idea how Adobe implements the white point transform for soft-proofing. All I can say is that there's certainly no change in the working space to printer direction.
The mechanism does appear to be part of the Adobe soft-proofing though. It would be very interesting to find out exactly how the soft-proofing is implemented (would you have any contacts in Adobe who could tell us?).
Robert
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I think you are using a profile made for one printer to give you an idea of OOG problems on another printer ... well, that will probably sort of work. Then I assume you're printing using sRGB with the printer managing the color - which is fine. But if you want to make the best of your printer then you would need to profile it for its full gamut and not restrict it to sRGB. Still, if you're happy with the way you're doing things then that's great!
Robert
You can't assume I'm printing in sRGB not even with my $50 Epson.
I don't believe anyone can know exactly what color space my Epson receives data seeing that my images data stays in ProPhotoRGB and gets passed to the printer driver using "Printer Manages Color" with a conversion (I'm assuming) through Mac OS Quartz driven data handling as mentioned often in discussions here on resolution upsampling by the OS printer pipeline on higher end Epsons.
Again since I can't know what's going on under the hood to make this happen I'm having to assume if the OS is manipulating resolution this way then it must be providing some kind of color description conversion for my dinky Epson to give me pretty darn close color matches with no clipped detail since the data is ProPhotoRGB sourced. It used to be many years back if I sent wide gamut encoded data using "Printer Manages Color" the results would be quite desaturated and butt ugly. No more.
All I know is what I thought would be way out of gamut color saturation levels (255 in sRGB) for a printer to reproduce viewed on my sRGB display and which used to print as flat blobs of posterized color, now prints just fine. No one has been able to explain how that happens under the hood. Even Walgreen's Fuji Frontier drylabs are reproducing detailed, saturated color (in sRGB space-255RGB clipped data) that used to print as flat blobs of dull color on a Noritsu about 8 years ago.
So from this observation I don't think it's possible or even beneficial to control everything in the screen to print pipeline at the levels of complexity and time devoted you're proposing. IMO it appears you're investing 90% of work time and effort to get back maybe 5% extra bit of precision in color matching no one is ever going to see in a print, not even your customers.
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So from this observation I don't think it's possible or even beneficial to control everything in the screen to print pipeline at the levels of complexity and time devoted you're proposing. IMO it appears you're investing 90% of work time and effort to get back maybe 5% extra bit of precision in color matching no one is ever going to see in a print, not even your customers.
Hey Tim,
Well, I have to say I don't agree with you there :). For sure I've put in a fair amount of time and effort into this, but there are many paybacks. The main one, of course, is that my printing has improved significantly, and it's now very rare that I get a print that is different to what I intended. Before investing in all of this, my first print was almost always wrong in some way or other, and I would have to reprint, maybe several times: very expensive and time-consuming!! The other big benefit is less easy to quantify, but it's down to understanding what's happening. So, for example, I do now understand the whole black-point, dMax, gamma thing and as a result I don't get clipping in the shadows any more (unless I want it): this may seem a small thing, but I think it makes a big difference to a print because the shadow detail gives lightness and body to the print.
But I'm a perfectionist and I like to know what's under the hood ... fortunately the world can accommodate all of us :).
Robert
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Hey Tim,
Well, I have to say I don't agree with you there :). For sure I've put in a fair amount of time and effort into this, but there are many paybacks. The main one, of course, is that my printing has improved significantly, and it's now very rare that I get a print that is different to what I intended. Before investing in all of this, my first print was almost always wrong in some way or other, and I would have to reprint, maybe several times: very expensive and time-consuming!! The other big benefit is less easy to quantify, but it's down to understanding what's happening. So, for example, I do now understand the whole black-point, dMax, gamma thing and as a result I don't get clipping in the shadows any more (unless I want it): this may seem a small thing, but I think it makes a big difference to a print because the shadow detail gives lightness and body to the print.
But I'm a perfectionist and I like to know what's under the hood ... fortunately the world can accommodate all of us :).
Robert
I'm going to have to assume you're printing on non-OEM printer paper and most likely non-glossy which would probably require extra effort for predictability.
I only print with OEM Epson glossy paper and ink so I don't need to be that perfect. But I still have to say there is way too many mysteries involved with my setup that doesn't make a lot of sense with regard to color gamut mismatches between screen and printer reproduction capabilities.
Below is my Soft Proofing and OOG mystery printing business cards without going to your lengths of print match predictability. Basically the results shown below are not suppose to happen according to what the technology says because that orange flower has clipped data in sRGB mainly in the greens and oranges but I still get a print match. I'm having to assume my $50 Epson has the same color gamut size as the more expensive Epson 7880 which doesn't make any sense.
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Basically the results shown below are not suppose to happen according to what the technology says because that orange flower has clipped data in sRGB mainly in the greens and oranges but I still get a print match.
Remember that Gamut warning do not tell you how much out of gamut the colour is. It may be 0,00001 DeltaE or 100 DeltaE. In your case it is probably so close that it doesn't matter. Besides, if you use perceptual rendering intent it tries to preserve tonal differences while remapping colours to match the gamut, theoretically preserving detail in OOG areas of the same colour.
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You can't assume I'm printing in sRGB not even with my $50 Epson.
I don't believe anyone can know exactly what color space my Epson receives data seeing that my images data stays in ProPhotoRGB and gets passed to the printer driver using "Printer Manages Color" with a conversion (I'm assuming) through Mac OS Quartz driven data handling as mentioned often in discussions here on resolution upsampling by the OS printer pipeline on higher end Epsons. >>
I do the same thing with my similar six color Epson. I print from ProPhoto using Photoshop manages colors and get just about the same result if I use printer manages. If I use the correct printer and paper profiles, I get a very good match to my screen plus better blues and reds. I'll be using wide gamut soon and we'll see if I have to adjust anything. I can do a hard proof with a few clicks and be confident that people with the right skills have worked very hard to produce that print.
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I do the same thing with my similar six color Epson. I print from ProPhoto using Photoshop manages colors and get just about the same result if I use printer manages. If I use the correct printer and paper profiles, I get a very good match to my screen plus better blues and reds. I'll be using wide gamut soon and we'll see if I have to adjust anything. I can do a hard proof with a few clicks and be confident that people with the right skills have worked very hard to produce that print.
Well there's nothing wrong with Printer Manages Color as opposed to Photoshop Manages Color as long as you are using the right profiles for the paper. All that happens is that the working space data is mapped to the printer/paper output by the printer driver in the first case, and by Photoshop in the second. It could well be that your printer driver does a better job of this than Photoshop. The printer driver will normally use the Apple ColorSync or Microsoft ICM engine whereas Photoshop uses Adobe ACE ... and maybe these do a better job in some cases. A comparison would be interesting.
Unless you use light near 5000K in your work environment, I don't see how your monitor image can match your print - side by side - because the white points will be different (unless you've adjusted your monitor to your working illumination). What does work quite well is not to view the two side-by-side, allowing the eye some time between looking at the print then at the monitor image - that way the eye adapts to the white point of each and compensates automatically (pretty amazing huh?).
Robert
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Remember that Gamut warning do not tell you how much out of gamut the colour is. It may be 0,00001 DeltaE or 100 DeltaE. In your case it is probably so close that it doesn't matter. Besides, if you use perceptual rendering intent it tries to preserve tonal differences while remapping colours to match the gamut, theoretically preserving detail in OOG areas of the same colour.
I'm aware of that. That wasn't the point I was making.
I'm now of the school of thought that we have put way too much faith and developed unreasonable expectations in the technology because we marvel at what it can do without our help but can only offer speculative answers to explain why.
You're not a color scientist. You didn't make any of the color reproduction devices. You don't know a lick about programming a computer to know when something works or doesn't with regard to controlling color processes. We tend to inject meaning and intent behind the process of capturing an image digitally and seeing it as some type of controllable object when it really is just software manipulating it all without our knowledge.
And we seem to be under the same misconception and assume by our ability to control this self imposed objectification of the technology consistently that it's designed to function that way. We assume when we fiddle with a knob here and tweak and measure some piece of analytical software in order to characterize the level of consistency we fool ourselves into thinking that when it isn't consistent that WE are the ones doing it wrong or not understanding correctly or the technology is broke and thus make ourselves go down a time wasting troubleshooting rabbit hole instead of just making it work by other easier methods.
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I'm aware of that. That wasn't the point I was making.
I'm now of the school of thought that we have put way too much faith and developed unreasonable expectations in the technology because we marvel at what it can do without our help but can only offer speculative answers to explain why.
You're not a color scientist. You didn't make any of the color reproduction devices. You don't know a lick about programming a computer to know when something works or doesn't with regard to controlling color processes. We tend to inject meaning and intent behind the process of capturing an image digitally and seeing it as some type of controllable object when it really is just software manipulating it all without our knowledge.
And we seem to be under the same misconception and assume by our ability to control this self imposed objectification of the technology consistently that it's designed to function that way. We assume when we fiddle with a knob here and tweak and measure some piece of analytical software in order to characterize the level of consistency we fool ourselves into thinking that when it isn't consistent that WE are the ones doing it wrong or not understanding correctly or the technology is broke and thus make ourselves go down a time wasting troubleshooting rabbit hole instead of just making it work by other easier methods.
Hi Tim,
I know this answer isn't directed at me, but I suspect you probably feel the same about my comments and questions, so I might venture a thought or two. I'm an electronic engineer with a post-graduate in computer science and I've spent most of my working life in software and hardware development, mostly in telecommunications but also in process control and instrumentation. So I have a reasonable background in maths and there are similarities between the sort of things that CMMs and profiles attempt and the sort of work that I've been involved in (especially in signal processing).
However ... I've only been looking at color management fairly recently (a few months), even though I've been a professional photographer for ten years now and have been doing my own printing for a while longer than that. There is a huge amount to it and it's very confusing, especially because software vendors like Adobe don't tell you what they're doing when they do something like turning Simulate Paper Color on in soft-proofing. So a lot of the time it's down to guess-work, and doing tests to see if the guess-work seems to be right or wrong ... and asking others who've been there before for their help.
You seem to feel that this is just a waste of time and that one's conclusions are quite likely to do more harm than good. But if you don't understand your tools you are equally likely to end up with a lesser product. For example, I've just watched Andrew Rodney's absolutely excellent Youtube video on DNG Camera Profiling ... and he reduces all the confusion around by explaining very clearly that what the profiling does is effectively to condition the raw image to the spectrum of the illuminant; and furthermore that the shape of daylight spectra does not change fundamentally with different times of day or cloud conditions or geographical location. So, as with a scalpel, he has cut down the muddle of potentially hundreds of profiles, just for outdoor photography, to just one profile. That's what understanding does.
So how can you know, before embarking on an attempt to understand things like soft-proofing, profiles, rendering intents, CMMs, illuminants, inks, papers, not to mention the eye and the psychology of vision etc., what you are going to find out? All that I can say is that I may irritate people with my questions (and I am sorry for that!), but I have learnt a huge amount and it's been well worth the effort and frustration.
Having said that, I do agree that experience and good judgement, and seeing the bigger picture, and not getting bogged down in detail to the detriment of the end result ... is equally important, if not more so. There really isn't much point in having a brilliantly color-managed system if the basic capture is badly framed, taken in flat light, over-exposed, badly developed ... and so on. But if that stuff is OK (always room for improvement!), then why not make the best of the technology, to the best of one's ability?
Or perhaps I've misunderstood your points?
Robert
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There is a huge amount to it and it's very confusing, especially because software vendors like Adobe don't tell you what they're doing when they do something like turning Simulate Paper Color on in soft-proofing. So a lot of the time it's down to guess-work, and doing tests to see if the guess-work seems to be right or wrong ... and asking others who've been there before for their help.
Well, the Simulate Paper White button (also called the make my image look like crap button) is actually pretty simple. Normally, when that button is off, Photoshop does an image to display profile color transform using a Relative Colorimetric rendering intent. When turned on it's doing an Absolute Colorimetric rendering intent using the paper white color data contained in the profile. With the button off, the white point of the paper is ignored in the screen display.
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... I would appreciate your advice on soft-proofing.
I think the first step to effective use of soft proofing is understanding its limitations, aka dialing down your expectations.
The current ICC model is for the most part based on point processes -- every pixel in the image goes through the same math when the color space is changed. This has the advantage of using the most-well-understood psychological data. However, there are spatial effects not embraced by the ICC model which pertain to the soft proofing experience. As an example, and I wish I had a reference for this, humans perceive colors differently if they think that the image source is self-luminous than if they think that it is just reflecting some illuminant. There were soft proofing environments in the 90s that went to elaborate lengths to disguise the fact that the subject was in fact observing a CRT.
Scale is important. I print 11x14s differently than 40x 60s.
The lighting level in the ultimate viewing environment is important.
The spectrum of the ultimate viewing illuminant is important.
The surround, and, generalizing, the state of adaptation of the viewer is important.
You get the idea.
When I get a print order that requires a size and/or medium that I've never used before, I make test prints. Small ones at first. Full sized ones if I think it's necessary. The soft proof provides a good starting place, but the test print is the truth. If I'm going to ask my customers to pay hundreds to thousands of dollars for a print -- depending on medium -- I owe them nothing less.
Jim
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Well, the Simulate Paper White button (also called the make my image look like crap button) is actually pretty simple. Normally, when that button is off, Photoshop does an image to display profile color transform using a Relative Colorimetric rendering intent. When turned on it's doing an Absolute Colorimetric rendering intent using the paper white color data contained in the profile. With the button off, the white point of the paper is ignored in the screen display.
Hi Jeff,
Well, I'm sure you must be right. However, my (very limited and incomplete) understanding is that an Absolute conversion will transform the image so that when the image is viewed under the specific illuminant it will be the same as the same image that had not been transformed, viewed under D50 (were it possible). In other words, given a perfect world, the Lab values measured by an instrument would match exactly the PCS values. So if the illuminant has a color temperature of 6500K, the image will be printed much warmer.
Simulate Paper Color will do the opposite, so that if the profile specifies an illuminant of 6500K, the soft-proof will look like an image that has been printed for D50 but viewed under 6500K lighting (in other words the soft-proof will be much bluer).
So I suppose what Photoshop may be doing is to first of all do a B2A Perceptual or Relative conversion, to get the gamut mapping sorted out, and then do an A2B Absolute transform to get the white point shifted. I guess that would give a fairly accurate soft-proof, depending on how good the profiles are, not to mention the CMM.
At any rate, if that's what's going on then it would explain how I can get an excellent soft-proof with Simulate Paper Color by modifying the 'wtpt' tag in the profile so that the (soft-proofed, simulate paper white) display white matches the illuminated paper white (when viewed side-by-side to allow for chromatic adaptation).
I can't say I agree with the statement "the Simulate Paper White button (also called the make my image look like crap button)". What I'm seeing is that the Simulate Paper White gives me an almost perfect match to my print ... when viewed side by side. Personally I think that's more like a magic button than a crap button :).
Robert
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I think the first step to effective use of soft proofing is understanding its limitations, aka dialing down your expectations.
I agree entirely.
The current ICC model is for the most part based on point processes -- every pixel in the image goes through the same math when the color space is changed. This has the advantage of using the most-well-understood psychological data. However, there are spatial effects not embraced by the ICC model which pertain to the soft proofing experience. As an example, and I wish I had a reference for this, humans perceive colors differently if they think that the image source is self-luminous than if they think that it is just reflecting some illuminant. There were soft proofing environments in the 90s that went to elaborate lengths to disguise the fact that the subject was in fact observing a CRT.
This article is worth reading:http://www.color-image.com/2012/02/monitor-calibration-d65-white-point-soft-proofing/ (http://www.color-image.com/2012/02/monitor-calibration-d65-white-point-soft-proofing/). Essentially we appear to have a choice when comparing a print to a soft-proof: a) do not attempt to view the monitor image and print at the same time, and make sure the monitor is at D65, b) make sure the white points of both print and soft-proof are the same and you can then view them side-by-side for direct comparison. Option b) has the disadvantage of not having the monitor at D65 (which is apparently the optimal setting for viewing an image on a display) - so the image should be processed at D65 and the monitor white only changed to match the paper illuminant for direct comparison. I have tried soft-proofing with a 6500K fluorescent and this does seem to work well ... the challenge will be to get a really good 6500K fluorescent tube!
So it would seem (at least possible) that while soft-proofing at the paper white, if the paper is beside the monitor and is illuminated to the target illuminant, that the eye will think that both paper and monitor have the same reflective light source and then the soft-proof gives a good match for what the print will look like. Certainly, in my tests that seems to be the case.
Scale is important. I print 11x14s differently than 40x 60s.
Definitely - I make sure the print and soft-proof are the same size and are viewed at the same distance and from the same angle. That means that we need to understand how a much larger print changes due its size and viewing distance ... and make appropriate adjustments before printing. What I also do is to zoom in to print-size and view the zoomed-in image from the normal viewing distance. This does help, but of course I can only see a part of the image at any one time. A big monitor helps.
The lighting level in the ultimate viewing environment is important.
The spectrum of the ultimate viewing illuminant is important.
Yes and yes. If you know all of these things at soft-proofing time then you can take them into account. In my case I generally don't (except for gallery prints) because my customers use all kinds of different lighting. So all I can do is to aim for a standard (I use Solux 4700K bulbs) and then check the print in different lights to make sure that there aren't any big problems that chromatic adaptation won't take care of.
When I get a print order that requires a size and/or medium that I've never used before, I make test prints. Small ones at first. Full sized ones if I think it's necessary. The soft proof provides a good starting place, but the test print is the truth. If I'm going to ask my customers to pay hundreds to thousands of dollars for a print -- depending on medium -- I owe them nothing less.
For sure. As much as possible I try to limit myself to 4 papers: Canson Platine for normal landscape, Canson Baryta or Hahnemuhle Photo Rag for black and white, Canson Photo High Gloss for images that I mount under acrylic. With time I'm getting a very good feel for these really excellent papers and I'm no longer wasting my time and money trying all kinds of different papers. But if, for some reason, I had to use a different paper ... well then I would absolutely do test prints until I was happy that my soft-proofing matched the prints.
Robert
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I can't say I agree with the statement "the Simulate Paper White button (also called the make my image look like crap button)". What I'm seeing is that the Simulate Paper White gives me an almost perfect match to my print ... when viewed side by side. Personally I think that's more like a magic button than a crap button :).
What Jeff is referring to is the dullness one often sees after invoking the paper simulation where the image looks crappy compared with the soft proof off. If you've got a paper and image with a lower dynamic range, seeing this turn on can look alarming, so just don't view the screen when it updates, your eyes adjust and it looks fine (and as you suggest, matches much better, hence the option).
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What Jeff is referring to is the dullness one often sees after invoking the paper simulation where the image looks crappy compared with the soft proof off. If you've got a paper and image with a lower dynamic range, seeing this turn on can look alarming, so just don't view the screen when it updates, your eyes adjust and it looks fine (and as you suggest, matches much better, hence the option).
Yes, I read Jeff's reply too early to get the humour :)
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I think I can confirm with reasonable certainty that what Photoshop/Lightroom does in soft-proofing is this:
- The image is converted to the chosen intent (normally Perceptual or Relative Colorimetric, but also Absolute or Saturation if that's what's chosen). This remaps the tristimulus values to the destination gamut.
- The image is then converted back to the working space using Absolute Colorimetric. This shifts the remapped XYZ values to the white point in the destination profile's 'wtpt' tag (in other words, the paper white).
This can be demonstrated quite easily by going through the process manually: Convert to the destination profile using Relative Colorimetric, say; then remap to the working space using Absolute. If you compare this to the original image with Soft Proofing and Simulate Paper color on you will get an exact match between the two (visually, or with an instrument).
Robert
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I'll try to summarize what I've learnt about soft-proofing in this forum over the last few days (and again, many thanks for your help!). What I’ve written here is based on my current understanding and may not be correct – if there are errors please let me know and I’ll correct this summary.
Converting the Document for Printing (or viewing on the web)
- Conversion from working space to working space: This will always be Relative Colorimetric (even if Perceptual, Saturation and Absolute can be selected). In fact, conversions using a profile that is matrix-based (as are the working spaces) always use Relative Colorimetric.
- Perceptual: The entire gamut is remapped so that even if all the colors in the document are within the destination gamut, the colors will all be shifted. The objective of this transform is to maintain the relation between colors, at the expense of color accuracy.
- Relative: Out-of-gamut colors are remapped to the nearest in-gamut color (on the gamut envelope). This may involve hue, saturation and or lightness changes, depending on the profile algorithm used (one of the things that distinguishes a good profile from a bad one is how well this mapping is done). The black and white points are mapped to the new colour space, so that the greys appear to remain grey even if this leads to some shifting of colours within the rest of the image. The profile attempts to preserve the relationship between colors given the white-black point shift. Colors nearer the grey line are shifted more, colors further from the grey line shifted less.
- Absolute: Exactly the same mapping is used as in Relative (the two share the same mapping tables) so that both gamut mapping and adjustment for the D50-normalized paper color occurs. However, all the colors are shifted so that they will retain their absolute value when viewed under the target illuminant (in fact, what happens is that the grey line is not adjusted, so that if the target illuminant temperature is warmer than D50, the print greys (and other colors) will have a blue tint). At any rate, the effect is that if the target illuminant has a very warm temperature of say 2800K and the print is viewed under a 5000K light, it will appear very blue. If the target illuminant is 5000K and the print is viewed under the 2800K light, it will appear very yellow. The idea is that when viewed under the target illuminant, the colors will retain their PCS Lab values. This rendering intent is rarely used in photography and for this reason it isn’t available in Lightroom.
- Saturation: This attempts to preserve highly saturated colors. It’s normally of no interest in photography unless graphic-like effects are desired.
- Black Point Compensation: This rounds the transition to the destination black. If BPC is not used, the transition will be abrupt, so that colors will suddenly get clipped to black as they get near the output black. With BPC on, the colors will gradually get squashed to black as they get near the output black. This avoids areas of flat black in the print.
- Paper Black: This is the blackest black that can be printed on this paper with the inks used. The paper black is also measured during profiling. Colors darker than this will be clipped to black. Black point compensation uses the paper black figure.
- Paper White: The paper white is measured during profiling and normalised to D50. The paper white is both the tint in the paper and the brightness of the paper (when viewed under the standard illuminant). The intent mapping tables are built to map the image to this white.
- Illuminant: The default illuminant is D50. Unless the profile takes the illuminant into account, D50 is assumed … in other words it’s assumed that we will view the print with a lamp which has a D50 spectrum (this is a daylight spectrum which can’t be achieved with artificial lamps). D50 has quite a flat spectral power distribution, so that all colors are equally well excited or represented. Lamps like 2800K tungsten are weak in the blues, a bit weak in the greens and very strong in the reds: with lamps like these, without compensation the blues will look darker and the reds brighter with greens a bit darker. Colors with combinations of the colors will be affected proportionally, so yellows , which are a combination of greens and reds will be brighter, and cyans, which are a combination of greens and blues will be darker. 6500K fluorescent lights have more power in the blues and less in the reds and they also have spikes along the spectrum due to the phosphors used. With this sort of lamp the blues will be brighter and the reds darker, and certain colors along the spectrum will be bumped up (by the spikes in the spectrum). Programs like ArgyllCMS have an option to measure the target illuminant and to incorporate the illuminant’s spectrum in the transform. Assuming that this is done well, it will improve the accuracy of the colors in the print for the target illuminant (in other words, it allows us to target the print to different lighting conditions like incandescent, fluorescent etc.). However, if we do not know what type of light the print will be viewed under it’s better not to use illuminant compensation as it could make things worse, for example if we target warm tungsten lamps and the print is actually viewed under 6500K fluorescents.
- Optical Brighteners: Optical brighteners are chemicals added to the paper and sometimes to the ink. These shift ultra-violet light to blue light, so the print looks ‘whiter’ … or bluer, in reality. As with illuminant compensation, programs like ArgyllCMS can attempt to adjust the print so as to counteract this effect … which is not something one would normally want to do as it would be defeating the ‘brightening’ effect. (In proofing, we normally want to be able to compare the print and the proof side by side, and so we may wish to eliminate the effect of the optical brighteners in both print and proof).
- Chromatic Adaptation: The eye has the ability to compensate for the illuminant when viewing paper. So we see the paper white as white, even though it may have a yellowish tint and even though the lamp may have a very warm color. This means that on the whole prints will look OK with very different lighting. However, it’s important to check the print under the possible lighting conditions that it will be viewed under because different lights, with different spectra, can cause colors to shift relative to one another, and the eye cannot compensate for that.
Soft-Proofing
Soft-proofing uses whatever intent is chosen (Perceptual, Relative …) and also Absolute when Simulate Paper White is selected.
- Converting for Print: The image is transformed (to a temporary soft-proofed image) using the chosen intent, exactly as above, so that the out-of-gamut colors are clipped and in-gamut colors are re-mapped.
- Black Point Compensation: Again, the soft-proofed image rounds the black transition if BPC is selected.
- Simulate Black Ink: This effectively lightens colors which are below the Paper Black to give an idea of what the print blacks will look like. It works with Black Point Compensation.
- Paper White: The soft-proofed image will be compensated for the paper white as for a normal conversion.
- Illuminant: If we know precisely what light the print will eventually be viewed under and if we can view the print with the exact same light, then we should use a profile that has illumination compensation and we should soft-proof with a profile that does not (same profile for same paper, one with illumination compensation, one without). If we do not know what light the print will be viewed under, then we should do the opposite: print without illumination compensation, soft-proof with. In either case the print and soft-proof should match. The reason why it’s better not to print with illumination compensation is that the compensation is only for a particular lighting condition: if the print is then viewed under different light, the compensation could make things worse, not better.
- Optical Brighteners: Same as for the illuminant. Unless we know the target illuminant and can view the print under it, we should print without compensation and soft-proof with.
- Simulate Paper Color: The soft-proofed image is converted back to the working space using the Absolute Colorimetric reverse table (that is the table that converts back from the destination colors to the PCS, or Profile Connection Space). The effect of this is to simulate the paper white because all the colors are shifted from D50 to the paper white under the target illuminant (so if the target illuminant is warmer than D50, the soft-proof will also be warmer). Since out-of-gamut colors have already been mapped in the first transform (image to destination) there will be no out-of-gamut colors in the Absolute conversion, so the colors should accurately reflect the printed colors, viewed under the specified illuminant. However, unless the white point is changed in the output profile, the paper white is normalised to D50, which means that the soft-proofed image will only match the print if the viewing light is very close to D50 (or unless the monitor white is changed … see below).
- Monitor Gamut: It’s very important to bear in mind that we are viewing the image on a monitor and that this has a different (and possibly smaller) gamut than both the working-space we are using and the destination (print or web) space. So there may be colors in the image that we cannot see, some which can be printed, and some which will be clipped on output. Lightroom has a useful feature in soft-proofing that allows out-of-gamut colors to be highlighted both for the monitor and for the destination. In Photoshop, it’s necessary to soft-proof to the monitor profile to see monitor out-of-gamut colors.
Viewing a Soft-Proofed Image
The whole objective of soft-proofing is to enable us to cut out the test print and go straight from the image viewed on the monitor to the final print, with considerable confidence that the print will look the same as the image on the monitor. It should allow us to see what happens to out-of-gamut colors, how in-gamut colors are shifted … and ideally what the print will look like under specific illuminants, like a tungsten lamp or a fluorescent lamp. This is a big objective, and to see if we come close to meet it, the best thing is to make some test prints and then compare them to the image on the monitor. We can do this in two main ways:
- Viewing separately: The soft-proof is looked at, some time allowed looking away from it, and then the print is looked at. The monitor should be at or near 6500K as this is the optimal viewing temperature for monitors. Simulate Paper Color should be left off, otherwise the image will look very yellowish (assuming that the viewing light is well below D50). What we are depending on here for comparing the soft-proof and the print is visual memory; allowing some time between viewing the soft-proof and the print gives time for the eye to adjust to the two different lighting types and temperature. In this case we are not attempting to see what the print will actually look like under a particular illuminant.
- Viewing Side-by-side: This is the ideal. However it is only ideal if the soft-proof and the print look the same when viewed side-by-side! It is possible to get this to work properly, but as it isn’t so easy I’ll cover it under its own heading below.
Side-by-side Viewing of a Soft-Proofed Image
When we look at a print, we see the paper white as being white, even if it is actually an off-white. The color of the paper depends on the illuminant, of course, so this compensation is for both the paper color and for the color of the light. It is called chromatic adaptation. Unfortunately the same adaptation doesn’t occur with a monitor display, so if the ‘white’ on the monitor is yellowish, we see it as yellowish. This means that an image on the monitor which is in absolute terms identical to a print may not look the same to us. An instrument may see the two as being identical, but we do not.
However, it is possible to fool the eye into thinking that the monitor image is actually a print, and then chromatic adaptation seems to work. If we view a print side by side with the monitor image so that they can be seen by the eyes at the same time, then the eye thinks they are both prints.
Furthermore, if a sheet of plain paper (the same paper that will be used to print on) is viewed side by side with the monitor image, under the target illuminant, then, again, the eye sees the monitor image as though it were a print being viewed under this target illuminant.
This means that if we set up our viewing environment carefully, that we can soft-proof an image on our monitor and see the soft-proof as though it were a print. This is the subject of many research papers and it isn’t cast-in-concrete science as there is as much psychology as biology involved, but it does seem to work for me.
There are two ways to set this up.
- Adjust the Monitor: This requires software like the NEC Spectraview or Eizo ColorNavigator. What we do is to view the paper beside the monitor, and visually adjust the display white until it matches the paper white. Again, it’s important to stress that the two must be viewed side-by-side while doing this. The calibration/profiling software then generates a new profile for the monitor based on this white point. To view the print side by side with the monitor, the profile is then changed from the normal 6500K profile to this adjusted profile; Simulate Paper Color is not used.
- Adjust the Destination Profile: As explained in Simulate Paper Color above, the white point in the destination profile is used by Photoshop/Lightroom to simulate the paper color. This white point is in a tag called ‘wtpt’. To adjust it to the print paper white, the following procedure can be used:
- With the illuminated (white) paper beside the monitor, create a new document in Photoshop and (in full-screen mode) adjust the Lab values so that there is a visual match to the paper white.
- Convert these Lab values to XYZ using http://www.brucelindbloom.com/index.html?WorkingSpaceInfo.html. The Ref. White must be D50. This gives the XYZ values for the paper white.
- Convert the paper profile (which should be made to D50) to xml using IccXML: http://sourceforge.net/projects/iccxml/
- Copy and paste the XYZ values from Bruce Lindbloom's calculator into the 'wtpt' tag in the xml version of the paper profile
- Change the ‘desc’ tag to append the illuminant condition (say ‘–Tungsten 2800K’)
- Save the modified xml file to a new filename with the illuminant condition appended (say ‘–Tungsten 2800K’)
- Convert the xml version of the modified profile to icc, again using IccXML
Ideally, the black point should also be adjusted, but this can’t be done visually (the colors are too dark to compare visually). However as an approximation, the values in the ‘bkpt’ tag in the xml file can be adjusted in proportion to the adjustment in the ‘wtpt’ tag: XBN = XBO*(XWN/XWO) where XBO is the Old Black X Value, XBN is the New Black X value, XWN the New White X value, XWO the Old White X value … and the same for the Y and Z values.
The modified profile can now be used to soft-proof: Simulate Paper will give the correct paper white for the lighting conditions used.
We need to go back to the original profile if we want to make further adjustments to the white point or brightness. What I do is to save the Lab adjusted image so that I can tweak the original Lab values. I also copy the values into a spreadsheet which computes the modified black point and I also save this spreadsheet for reference.
I personally prefer the second method as it can be used on monitors that don’t have profiling software which allows visual adjustment of the white point, and because once it’s set up the soft-proofing Simulate Paper White works properly as it is designed to work, and there is no need to change monitor profiles. However, the first method works just as well, so it’s a matter of preference and what monitor software you have.
Other Factors
There are other factors to take into account when soft-proofing images. For example, the images should be the same size and viewed from the same distance away and at the same viewing angle; the brightness of the paper and (soft-proofed) monitor white should be the same (or very close to each other); the soft-proof should be viewed in full-screen mode with a dark background (not possible in Lightroom at present … may be a reason to prefer adjusting the monitor white to adjusting the destination profile); there should be no bright colors in the room; ideally the only thing that should be lit is the print (the reflected light is normally bright enough to work in); … and no doubt other things!
I hope this will be of use to you. Again, many thanks for your help!
Robert
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Scale is important. I print 11x14s differently than 40x 60s.
Jim
I know this is off topic, but I have been reading up on what others do regarding changes from printing a small print to a large one ... curious what you do “differently”.
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I know this is off topic, but I have been reading up on what others do regarding changes from printing a small print to a large one ... curious what you do “differently”.
I would be interested to hear what Jim says about this ... but I find that two main things need to be changed: the sharpening and the saturation. The saturation needs to be quite selectively done because what happens is that where there is quite a bit of fairly high-frequency stuff, like the reeds in this crop, the large image appears less saturated than the small one (because the reeds are closer together in the small print they appear more saturated):
(http://www.irelandupclose.com/customer/LL/Big-Small-Print.jpg)
For the same reason I only use a very, very light sharpening before upsizing (just development sharpening) and then apply sharpening with a small radius to the upsized image where there is high-frequency stuff (and more sharpening if necessary elsewhere in the image). This is why I always size the image in Photoshop before printing, even though I use Lightroom to print.
I don't have a formula for that ... I just gauge it image by image. But certainly, if you are soft-proofing side-by-side it is important to view same size, same distance, same viewing angle of 90 degrees.
Robert
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I know this is off topic, but I have been reading up on what others do regarding changes from printing a small print to a large one ... curious what you do “differently”.
Wayne, I haven't codified it, and I don't make that many large prints, so I don't have it dialed in. In general, I think you need a little bit more drama (local contrast, chroma) in a small print than a large one. If you viewed them both at the same distance, I don't think that would be true, though. Correction: If you viewed them at different distances so that they both subtended the same visual angle, I don't think that would be true, though.
Jim
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I think I can confirm with reasonable certainty that what Photoshop/Lightroom does in soft-proofing is this:
- The image is converted to the chosen intent (normally Perceptual or Relative Colorimetric, but also Absolute or Saturation if that's what's chosen). This remaps the tristimulus values to the destination gamut.
- The image is then converted back to the working space using Absolute Colorimetric. This shifts the remapped XYZ values to the white point in the destination profile's 'wtpt' tag (in other words, the paper white).
This can be demonstrated quite easily by going through the process manually: Convert to the destination profile using Relative Colorimetric, say; then remap to the working space using Absolute. If you compare this to the original image with Soft Proofing and Simulate Paper color on you will get an exact match between the two (visually, or with an instrument).
Robert
But you can only do Relative in Photoshop/LR. The working space profiles do not have the other three intents. I'm not sure if this is true of Soft Proof, but I believe it is. So you only get Relative no matter what you select. The only way to see intents is to print them unless you can find profiles with all intents and install them.
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But you can only do Relative in Photoshop/LR. The working space profiles do not have the other three intents. I'm not sure if this is true of Soft Proof, but I believe it is. So you only get Relative no matter what you select. The only way to see intents is to print them unless you can find profiles with all intents and install them.
No, soft-proofing uses the destination profile, so as long as this profile is table-based and not matrix-based the soft-proof can be in any of the intents (Perceptual, Relative Colorimetric, Saturation or Absolute Colorimetric in Photoshop, Perceptual or Relative Colorimetric in Lightroom).
I think the mapping is as follows:
a) Simulate Paper Color Off:
Working Space -> PCS: Relative Colorimetric.
PCS -> Destination: Uses the destination profile (PCS to Destination BtoA table) and whatever mapping intent is chosen.
Destination -> PCS: Uses the destination profile (Destination to PCS AtoB table) and whatever mapping intent is chosen.
PCS -> Working Space: Relative Colorimetric.
So Working Space <-> PCS is always Relative Colorimetric, but PCS <-> Destination may be any of the intents.
a) Simulate Paper Color On:
Working Space -> PCS: Relative Colorimetric.
PCS -> Destination: Uses the destination profile (PCS to Destination BtoA table) and whatever mapping intent is chosen.
Destination -> PCS: Uses the destination profile (Destination to PCS AtoB table) and Absolute Colorimetric intent.
PCS -> Working Space: Relative Colorimetric.
By using Absolute Colorimetric reverse mapping the software simulates the paper color.
At least ... that's how I think it works!
Robert
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... the challenge will be to get a really good 6500K fluorescent tube!
This is an interesting problem. CRI, the specification for color accuracy, is based on perception, not on the actual color rendition of the lamp, so it is somewhat meaningless. I have been using 6500K reflector CFLs in recessed ceiling fixtures and I have been very happy with my print results, even though these lamps only have a CRI of 80. BTW, I am migrating to 6500K LEDs as these burn out. They cost more, but last longer and eliminate other problems caused by CFLs. CFLs may last a long time, but only if you don't turn them off and on! Also, instead of the steady current flow used by incandescent lamps, they draw huge current spikes for very short periods of time, which plays havoc with the Arc Fault Circuit Interrupters (AFCIs) that are specified by current U.S. electrical codes.
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This is an interesting problem. CRI, the specification for color accuracy, is based on perception, not on the actual color rendition of the lamp, so it is somewhat meaningless. I have been using 6500K reflector CFLs in recessed ceiling fixtures and I have been very happy with my print results, even though these lamps only have a CRI of 80. BTW, I am migrating to 6500K LEDs as these burn out. They cost more, but last longer and eliminate other problems caused by CFLs. CFLs may last a long time, but only if you don't turn them off and on! Also, instead of the steady current flow used by incandescent lamps, they draw huge current spikes for very short periods of time, which plays havoc with the Arc Fault Circuit Interrupters (AFCIs) that are specified by current U.S. electrical codes.
You might want to check out Walmart's new addition 5000K 900 Lumens Daylight LED bulb for about $9. I got two of them and their color rendering is surprisingly quite accurate enough. They even pass my trusty cadmium vs lemon yellow color rendering test which all daylight balanced CFL's that I've bought over the years don't do so well on. Under those lights and even some other LED's cadmium yellow appears lemon yellow (more cyan).
Below is a shot of the 5000K Walmart LED installed in my overhead oven light fixture. It's quite accurate to the way these lights render color. No print viewing light is going to render every color exactly as it should but this LED bulb does a decent job.
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A case for ProPhoto??
It has just occurred to me (and I'm not sure I'm right) that using a color space smaller than the print color space could cause soft-proofing errors. Here is the reasoning:
Consider a soft-proof with Simulate Paper using Perceptual from Adobe RGB to the RGB destination profile.
What happens, I think, is: RelCol from ARGB to PCS, Perc from PCS to RGBDest, AbsCol from RGBDest to PCS, RelCol from PCS to ARGB.
There could be gamut-clipping from PCS to RGBDest (which is OK from a soft-proofing point of view).
There could also be a gamut-clipping from PCS to ARGB, I think, which would not be OK from a soft-proofing point of view. There are two reasons (I think) for the potential OOG clipping:
- The AbsCol from RGBDest to PCS will shift the colors and so some of these may no longer be within the ARGB gamut.
- The Perc from PCS to RGBDest will stretch the ARGB gamut to the RGBDest gamut (if the RGBDest gamut is larger than the ARGB gamut). So on the RelCol return from the PCS to ARGB there will be clipping.
If this is correct then it makes a very good case to use a large working space gamut like ProPhoto, to make sure the working space is larger than the print space. (Of course there is a good case anyway to use a larger working space than destination space to prevent clipping on output, but I hadn't considered the effect on soft-proofing).
Robert