Luminous Landscape Forum
Raw & Post Processing, Printing => Colour Management => Topic started by: Doug Gray on January 15, 2016, 02:36:06 am
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One of the mantras in color management is that Perceptual Intent compresses colors near the gamut boundary so that it can map colors that are outside the gamut smoothly to the inside. For instance see the nice graphic illustrating Perceptual v. Relative:
http://www.cambridgeincolour.com/tutorials/color-space-conversion.htm
Note how perceptual maintains smooth color gradations throughout by compressing the entire tonal range, whereas relative colorimetric clips out of gamut colors (at center of magenta globules and in the darkness between them).
Apparently not very much if at all. At least on the profiles I've been using. Perceptual Intent does have a slight effect on tone. It implements a small "S" curve and changes luminance. But these changes are fairly small. As for compressing colors near the boundary and mapping outside colors smoothly inside as per the illustration it seems this may not be all that common. In fact it pretty much doesn't occur on I1Profiler or Profile Maker 5. The following data used profiles generated from identical spectral data using a Canon 9500 II with Epson Ultra Prem. Glossy.
Attached are 2 sets of 6 graphs, showing the actual profile responses of I1 Profiler and PM5 as the b* component of L*a*b* is swept from -127 to 127. The L* source is constant at 50 (mid gray), and a* is set to 0.
The individual graphs have the requested color component shown in red, the returned color shown in blue. In general the graphs on the right roundtrip using Perceptual out and Relative In. The profile is telling us what the actual color (this is what Relative does) generated by the Perceptual Intent is. The right hand graphs are Colorimetric. That is Relative in, Relative out. The profiles attempt to match all colors in gamut and map out of gamut colors to the nearest gamut boundary. They do a pretty good job.
The detailed descriptions are, from left to right, top to bottom:
1. Roundtrip using Perceptual Intent to the device and Relative Intent back to L*. Notice the big difference between the I1Profiler (top set) and PM5 (bottom set). The I1 has the L* actually drop to 48 as the gamut boundaries (b* less than -80 or more than 80) are reached. OTOH, PM5 sets the L* values just over 52 over the gamut. Different "secret sauces."
2. Roundtrip using Relative Intent to the device and Relative Intent back to L*. Both profiles do a reasonable job of keeping the L* at 50. The I1 profile is a bit better, probably because it has 36 LUTs on a side compared to 32 for PM5.
3. This shows the requested color b* component in red, the actual color printed in blue. Note how closely aligned they are until they hit gamut boundary. Oddly, the Perceptual intent clips at a slightly lower value than the Relative Intent roundtrip shown in the graph just below. This is really just an effect of Perceptual's gradual reduction of L* from 50 to 48 which decreases the b* gamut boundary. But evidence of gamut compression? I see only a very small rounding of the blue line near the boundary.
4. Same as #3, but is an expanded, right hand side only to make comparing the lines a bit easier.
5. This shows a Relative Intent in, Relative Intent out roundtrip. Here, the specific goals in the ICC spec. are to print the specified colors are closely as possible when within the gamut and map them to the gamut boundary when outside. They track quite closely until just past 80.
6. Same as #5, but is an expanded, right hand side only to make comparing the lines a bit easier.
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Thank you. Confronting what people believe with what really happens is the most important part of science, and happens far too rarely in many, many fields...
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This using the default settings in iProfiler for the perceptual rendering intent, not changing the contrast, saturation, or neutralize gray parameters?
Brian A
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This using the default settings in iProfiler for the perceptual rendering intent, not changing the contrast, saturation, or neutralize gray parameters?
Brian A
Yep. Just the default settings. It would be interesting to test the "neutralize gray" settings as it isn't really that clear what this is intended to do. Contrast is almost certainly related to "S" curve strength. When this is done in Photoshop with RGB curves it also increases saturation while just changing L* in a profile B2A0 map would not. It would be interesting to investigate what the saturation setting does.
It's fairly easy to test Perceptual mappings because you can find the colors they are mapped to by using the profile's A2B1 which gives you the Lab color that would be printed within reasonable accuracy.
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isn't the neutralize gray setting designed to remove the influence/bias of paper white from light grays? In a perfect world the greys would be along the L axis but once you introduce non-white paper base, they depart the axis.
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isn't the neutralize gray setting designed to remove the influence/bias of paper white from light grays? In a perfect world the greys would be along the L axis but once you introduce non-white paper base, they depart the axis.
Interesting I'll look at that specific issue.
Relative to the other settings, There is no significant difference in mapping until low L* values are reached where BPC dominates. Oddly, for the Chroma Plus settings in PM5 saturation is increased slightly at about 5% for the blue parts of the b* over the length of b* from 0 to -100 and it cuts off earlier. However, no compression or mapping of out of gamut color occurs. Just slightly increased saturation and only on the blue side of b*. I guess that is why it's called Chroma Plus.
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isn't the neutralize gray setting designed to remove the influence/bias of paper white from light grays?
Yes.
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isn't the neutralize gray setting designed to remove the influence/bias of paper white from light grays? In a perfect world the greys would be along the L axis but once you introduce non-white paper base, they depart the axis.
It does. I just checked it. As Andrew also said, neutral gray removes the effects of the paper white. That isn't possible at the highest L* values so from L*=85 to L*=100 the a* and b* values move gradually back towards the paper white with about half the distance to paper white recovered at L=95.
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It does. I just checked it. As Andrew also said, neutral gray removes the effects of the paper white. That isn't possible at the highest L* values so from L*=85 to L*=100 the a* and b* values move gradually back towards the paper white with about half the distance to paper white recovered at L=95.
Interesting. Wonder how a pure RGB grayramp looks printed that way viewed under a 4700K Solux lamp? In CMYK commercial press work we never even got that exacting and the grays still looked just fine.
The one thing I'm trying to understand since I don't have gray ink (if that's what's discussed here) over inkjet CMYK gray mixing is that the lighter the gray the more it requires paper white to show through in order to make it light. The mixture must have to reduce black considerably in order for that to happens since it's the most densest ink. That means CYM must adjust it's mixture ratio to maintain neutral gray to fight the staining effect of paper white.
So I'm asking is there really that much of a visual difference in compensating for non-neutral paper white?
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Interesting. Wonder how a pure RGB grayramp looks printed that way viewed under a 4700K Solux lamp? In CMYK commercial press work we never even got that exacting and the grays still looked just fine.
The one thing I'm trying to understand since I don't have gray ink (if that's what's discussed here) over inkjet CMYK gray mixing is that the lighter the gray the more it requires paper white to show through in order to make it light. The mixture must have to reduce black considerably in order for that to happens since it's the most densest ink. That means CYM must adjust it's mixture ratio to maintain neutral gray to fight the staining effect of paper white.
So I'm asking is there really that much of a visual difference in compensating for non-neutral paper white?
I can see the effect soft proofing a gray ramp. The Paper has a pretty noticeable blue tint (b* goes to -7 at the white point). looks sort of strange. The tones below L90 or so look reddish compared to the full "white" at L100. I prefer the paper gray which maintains the proper adapted color to the paper white. There is virtually no difference with neutral papers that don't have OBs.
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Interesting. Wonder how a pure RGB grayramp looks printed that way viewed under a 4700K Solux lamp? In CMYK commercial press work we never even got that exacting and the grays still looked just fine.
The one thing I'm trying to understand since I don't have gray ink (if that's what's discussed here) over inkjet CMYK gray mixing is that the lighter the gray the more it requires paper white to show through in order to make it light. The mixture must have to reduce black considerably in order for that to happens since it's the most densest ink. That means CYM must adjust it's mixture ratio to maintain neutral gray to fight the staining effect of paper white.
So I'm asking is there really that much of a visual difference in compensating for non-neutral paper white?
There is no gray without white pigment. There is a reason why Epson has K, LK, and LLK labeled inks. They are just diluted blacks.
Brian A
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Interesting difference in how I1Profiler and PM5 do Perceptual Intent across the L* range.
PM5 does not do any tone curve modifications but does a full BPC. I1Profiler does a partial BPC down to L=4 so at L:8, the paper's BP, the actual L is at 11. It continues to drop until L=4 (L=8 on the paper) then stays at L=8. It also does a slight, midrange contrast increase as a small "S" curve. At L:35 it drops L by 1, and at L:75 it increases L by 2 on a glossy with BP at L=8. On a matte with BP=23, BPC is also done down to L=4 and the "S" curve is added. However, the paper's BP is so high that it overrides most of the midrange contrast increase.
The I1Profiler profiles were v4 so it might be that X-Rite is following the ICC reference medium model for Perceptual Intent.
EToA:
I tested the partial BPC in Photoshop and Photoshop shows a full BPC rather than a pedestal from L=0 to 4. Odd. I examined the B2A0 LUT path and, guess what, it implements the Lab 0 to 4 pedestal in the "B-Curve section for the L channel only. The 3D LUTs get their input from the "B" curves. Other LUT paths such as B2A1 and all PM5 paths have a one to one B curve. Best guess is that Photoshop is simply ignoring the "B" curve component and assuming it is one to one as they have always been that way.
So now the question is, is this just in Photoshop's internal profile conversions or do they actually ignore the "B" curve when printing. Either way Adobe's CME is broken even if only slightly. Time for a physical print test.
EToA:
Ran a Photoshop print test and the L=4 pedestal does not appear. So Photoshop is printing the same way it's soft proofing works.
The problem is that Photoshop is NOT using the V4 "B" curves in the B2A0 tables. Most likely because "B" tables are new to ICC V4 as are the output reference medium specified in V4.
Selecting ICC V2 in I1 Profiler is probably a good idea for anyone using Perceptual Intent as it eliminates the pedestal and does a full BPC like PM5 but still has the contrast enhancement at the default settings.
As a side note, the "neutralize grays" slider at 0 is similar to the "paper colored gray" selection in PM5. However, putting the slider at 100 does not produce actual neutral grays in the manner of PM5. It just makes the grays about halfway closer to neutral. Not that this is very useful since this is mostly an issue with OBs and most people don't want the paper white to be a different hue from the grays in these.
Also, the results with the I1Profiler re gamut compression are unchanged in V2.
EtoA:
After examining the "B" curve detail in the V4 profile the B2A0 black point is exactly at L=3.16, not 4. This implements the dynamic range of the Standard References Medium black (Dmax:2.45) which is new to V4.
Basically, Photoshop ignores the "B" curve and treats it as a no-change transform. Effectively this results in full BPC (infinite dynamic range) in Perceptual for V4 which makes it the same as V2. Photoshop does implement the variations between V2 and V4 LUT coding. These would cause small differences, a bit less than 1 dE, between V2 and V4 had they not been done correctly. In V4 these 3D LUTS are tagged: lutBToAType. In V2 the 3D LUTs are tagged:lut16Type.
In summary, aside from Photoshop ignoring the "B" curves in Perceptual Intent on I1Profiler V4 profiles, Photoshop does accurately render exactly the same on the Relative Colorimetric A2B1 and BtoA1 paths to within digitization error ( < +/-.01 on L*, a*, or b*).
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Not really a surprise, given that these profilers have no way of knowing what the source gamut is.
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Not really a surprise, given that these profilers have no way of knowing what the source gamut is.
So true. But I wonder how the notion became so widely circulated. For a long time I believed it as well. It may be something that is largely in device link profiles.
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I've noted that commercial printing software adds a bit of perceptual rolloff to the relative intent, that is it doesn't clip colors straight off like the original ICC intention. That together with blackpoint compensation makes the relative intent sort of perceptual on steroids. When I print I use relative colorimetric with blackpoint compensation with either say Lightroom/Photoshop or a pre-processed file using LCMS tifficc.
If you want the "correct" relative colorimetric without BPC and with straight off clipping you find it in Argyll processing the file with cctiff.
The problem with perceptual ICC profiles is that it's hardcoded for a specific source gamut, so it may compress stuff even if it's not necessary. It's then more flexible this nonstandard way to do the perceptual compression in the printing software itself which knows both the source gamut and the actual colors in the file printed.
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I've noted that commercial printing software adds a bit of perceptual rolloff to the relative intent, that is it doesn't clip colors straight off like the original ICC intention. That together with blackpoint compensation makes the relative intent sort of perceptual on steroids. When I print I use relative colorimetric with blackpoint compensation with either say Lightroom/Photoshop or a pre-processed file using LCMS tifficc.
I would be interested in further information about this. ICC V4.3 specifically disallows this in Relative Colorimetric intent. Along the same lines I have seen some canned profiles implement black point "correction" in Colorimetric Intent when it should be limited to Perceptual and optionally, Saturation. Perfectly OK in Perceptual Intent but it hoses over soft proofing when included in Relative. ICC has made it clear that the proper implementation of both V2 and V4 profiles should not implement BPC. It has documented Adobe's proposal for optionally including BPC when desired as it sometimes is but that is to be done by the color engine, not the AToB1 or BToaA1 LUTs.
If you want the "correct" relative colorimetric without BPC and with straight off clipping you find it in Argyll processing the file with cctiff.
Matlab doesn't implement BPC either. It is, fortunately, a rather simple process to implement Adobe's BPC in Matlab which I have done. I have a function, "ProfileConvert" which has the that option. It converts colors into XYZ, find the BP by inspecting AToB0, scales XYZ against that then converts back to LABPCS and implements the BToA conversion.
The problem with perceptual ICC profiles is that it's hardcoded for a specific source gamut, so it may compress stuff even if it's not necessary. It's then more flexible this nonstandard way to do the perceptual compression in the printing software itself which knows both the source gamut and the actual colors in the file printed.
This seems to be the case for embedded profiles in printer drivers where the "Printer Handles Color Management" since the source colorspace is usually sRGB or sometimes Adobe RGB. The problem with generic ICC profiles is they have no idea what the actual image source colorspace is. When it's sRGB they can and sometimes do expand sRGB somewhat into the printer's colorspace where possible within limits as to what looks good. This isn't possible when they don't know the source colorspace.
See the thread here where I examined this as done by Canon 9500 II.
http://forum.luminous-landscape.com/index.php?topic=107556.0
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I would be interested in further information about this. ICC V4.3 specifically disallows this in Relative Colorimetric intent.
I haven't investigated it in detail so I don't have any specific information, I've just noted that it happens, and I think it breaks the ICCv2 standard too. But it's there because it's practical for real use. The blackpoint compensation thing was as far as I know a thing introduced outside standards by Adobe as it was practical for real use, and then it has later been defined and standardized. Adobe through it's de-facto monopoly has incredible power when it comes to introducing stuff like this.
I think the feature is good though, and I'm not particular fond of the hard-coded in the profile perceptual mode. It was good to have things precalculated back in the 90s when we didn't have much processing power in the computers, but nowadays I think it's better to have less hard-coding in the profile and do more image-dependent adjustments in the software.
I would guess that it's still made pretty static though, I don't think there's really any complex perceptual style gamut mapping going on, but just a short rolloff close to the gamut edge that looks a bit smoother than straight off clipping.
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But it's there because it's practical for real use. The blackpoint compensation thing was as far as I know a thing introduced outside standards by Adobe as it was practical for real use, and then it has later been defined and standardized. Adobe through it's de-facto monopoly has incredible power when it comes to introducing stuff like this.
It was introduced in the Adobe CMM (and later other's) to account for a 'bug' in mapping of black in some profiles that themselves were considered by Adobe broken. So it seems that spec's or not, profile creators have their own agendas and can produce bugs. I haven't seen profiles that are broken and need BPC in years. BPC either helps fix the bug or doesn't do anything. At least that's the idea and my experience.
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It was introduced in the Adobe CMM (and later other's) to account for a 'bug' in mapping of black in some profiles that themselves were considered by Adobe broken. So it seems that spec's or not, profile creators have their own agendas and can produce bugs. I haven't seen profiles that are broken and need BPC in years. BPC either helps fix the bug or doesn't do anything. At least that's the idea and my experience.
Uhm, I thought black point compensation was the thing that caused relative colorimetric to rolloff to black point of the paper rather than just clip at the darkest color the paper could reproduce? As far as I know, please correct me if I'm wrong, the original intent of relative colorimetric is to clip the gamut straight off not only in the brightest spots, but also in the darker areas.
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Uhm, I thought black point compensation was the thing that caused relative colorimetric to rolloff to black point of the paper rather than just clip at the darkest color the paper could reproduce? As far as I know, please correct me if I'm wrong, the original intent of relative colorimetric is to clip the gamut straight off not only in the brightest spots, but also in the darker areas.
My understanding is BPC does something useful or nothing at all depending on the profile. IF it's buggy as I saw a few decades ago, black is mapped correctly from source to destination using BPC. If the profile is kosher, nothing happens, no compensation is required. Again, I haven't see an output profile that produced goofy black mapping in a very long time. But I haven't tested every profile building app out there.
With those old, buggy profiles, without BPC, the conversion didn't look correct too; you could see this in blacks of course.
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Here's Adobe's submission. It's now in ISO 18619
http://www.color.org/BlackPointCompensation.pdf
If implemented, it should be optionally done by the CME. It's not a part of the ICC spec.
It's main use these days is when using Relative Intent when the source image has materially darker grays than the destination profile. Proper RI tables in both V2 and V4 profiles will clip at the media's black density limit. Some vendors had done BPC in the RI tables in the past but this is prohibited in V4 and strongly discouraged except for in house use for V2.
Perceptual Intent seems to have always implemented BPC so selecting that in PI does little if anything. At least I've never run across a PI that didn't.
There is a minor weirdness. V4 profiles force a BP at approximately L=3 to match the standard output reference medium but in the PI only. There is a discussion of this in the FAQ. I1Profiler's V4 implements this small clip in the Curves front end before the LUTs. Photoshop ignores it so you get a full BPC like in V2 PIs. LCMS doesn't. It's a nearly invisible effect.
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Perceptual Intent seems to have always implemented BPC so selecting that in PI does little if anything. At least I've never run across a PI that didn't.
Unlike the V4 spec., nothing in the V2 spec. says that P/SI has to map to/from a reference black point. Some particular vendors may have been doing this forever in their V2 profiles, but they seem to have kept that bit of "secret sauce" to themselves. So BPC does have uses for R.Colorimetric, Perceptual and Saturation profiles, depending on where they come from.
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Unlike the V4 spec., nothing in the V2 spec. says that P/SI has to map to/from a reference black point. Some particular vendors may have been doing this forever in their V2 profiles, but they seem to have kept that bit of "secret sauce" to themselves. So BPC does have uses for R.Colorimetric, Perceptual and Saturation profiles, depending on where they come from.
There really are no conditions that apply to PI. At least it V2. There could be and probably are PI profiles that might need BPC. I just haven't run across them outside of the L=3 clip in V4 which is ignored by Photoshop. Might even be of some use to me in Photoshop if they get around to being V4 compliant.
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While this topic is mostly about gamut clipping for the highly saturated colors printers can print but that are outside sRGB and aRGB there is a small difference between RI and PI in the way colors that are not printable are mapped into printable ones.
Here's a chart, in sRGB, of color gradients which are all in sRGB but the left hand saturated side is not printable. It shows what colors are printed instead for Perceptual Intent as well as Relative Intent. The requested color starts on the left with the unprintable color and gradually desaturates, keeping the same hue, to a fully desaturated gray on the right. In each group of 3 gradients, the first gradient is the requested color. The second is the color rendered with Relative Colorimetric and the third is rendered with Perceptual Intent.
The printer was a Canon 9500 II with a Baryta semigloss, no OBs and an I1Profiler profile. Default settings, V4, large LUTs.
You can download this image and soft proof to your printer and profile to see how closely these results match a different setup.
Some observations:
Notice the well known blue to magenta hue shift as the chrominance drops on the middle set on the right hand side. This effect is due to an apparent hue shift in certain colors even though the actual Lab hue is constant.
The major difference I see between the PI and RI stripes compared to the image stripe is that the PI portions that are out of gamut seem slightly closer visually than the RI even though the RI dE is somewhat greater. That's clearly a conscious decision to map colors for a better perceptual map at the expense of a higher dE.
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Notice the well known blue to magenta hue shift as the chrominance drops on the middle set on the right hand side. This effect is due to an apparent hue shift in certain colors even though the actual Lab hue is constant.
Can you explain what you mean in a little more detail?
"actual Lab hue" being constant in blues would mean that it wouldn't appear to be constant due to Lab warping (perceptually) in the blues.
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Can you explain what you mean in a little more detail?
"actual Lab hue" being constant in blues would mean that it wouldn't appear to be constant due to Lab warping (perceptually) in the blues.
Exactly. That was what I was noting but it was just an observation unrelated to printing or Perceptual or Relative Intent. The top stripe of each 3 stripe set is constant Lab hue which means a/b is constant. To best see the blue->purple shift block out the lower two stripes in the group of three.
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I have both applications being discussed here, and to tell you the truth, neither is worth a crap for Perceptual rendering. I have used Gretag's Perceptual rendering for certain files going to offset press - one that I particularly remember was a lime green graphic on the side of a jet ski. Went completely flat under Relative but was fully delineated under Perceptual, but because Perceptual fucked up the entire rest of the image, I did what I almost always do when needing Perceptual for offset - make two conversions and layer the Perceptual on top of the Relative and paint it in just where it's needed. Worked like a charm and printed exactly as expected with the printing house wondering how I did what I did. This is not such a big deal for inkjet as the gamuts are generally much larger than offset, but it's still too bad that you basically can't do that anymore.
As far as Relative Colorimetric, actual printed output always looked just a RCH better from ProfileMaker as compared to Profiler, but most people would never ever see the difference in the real world. And, of course, Gretag had/has hands down the best profile editor I've ever used.
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I have both applications being discussed here, and to tell you the truth, neither is worth a crap for Perceptual rendering. I have used Gretag's Perceptual rendering for certain files going to offset press - one that I particularly remember was a lime green graphic on the side of a jet ski. Went completely flat under Relative but was fully delineated under Perceptual, but because Perceptual fucked up the entire rest of the image, I did what I almost always do when needing Perceptual for offset - make two conversions and layer the Perceptual on top of the Relative and paint it in just where it's needed. Worked like a charm and printed exactly as expected with the printing house wondering how I did what I did. This is not such a big deal for inkjet as the gamuts are generally much larger than offset, but it's still too bad that you basically can't do that anymore.
As far as Relative Colorimetric, actual printed output always looked just a RCH better from ProfileMaker as compared to Profiler, but most people would never ever see the difference in the real world. And, of course, Gretag had/has hands down the best profile editor I've ever used.
Profile editing is not for the faint of heart. The biggest risk is messing up the relationship of the AtoB and BtoA tables which should be the inverse of each other. This then affects softproofing. I played a bit with it but made more of a mess than anything useful. Glad you were able to get it to work to your satisfaction.
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Profile editing is not for the faint of heart. The biggest risk is messing up the relationship of the AtoB and BtoA tables which should be the inverse of each other. This then affects softproofing. I played a bit with it but made more of a mess than anything useful.
It was pretty darn easy using Photoshop and Kodak's long gone Custom Color ICC. I still run it from time to time on a very, very old Mac. And yes, you can edit either or both table so there's no mismatch in what you get and what you see. Sometimes profiles only need one table edited, sometimes both.
As for GMB's profile editor, it was a huge mess of a GUI and one of the most incomprehensible products I've ever used. Editing a profile by editing images in Photoshop? Super easy.
Anyone here old enough to remember editing profiles using ColorBlind Edit? Pretty good too, not close to what Kodak provided however. What toolset for editing colors to affect a profile is more powerful and well know as Photoshop? I begged Thomas Knoll often to allow us to use PS to do this, never happened.
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It was pretty darn easy using Photoshop and Kodak's long gone Custom Color ICC. I still run it from time to time on a very, very old Mac. And yes, you can edit either or both table so there's no mismatch in what you get and what you see. Sometimes profiles only need one table edited, sometimes both.
As for GMB's profile editor, it was a huge mess of a GUI and one of the most incomprehensible products I've ever used. Editing a profile by editing images in Photoshop? Super easy.
Anyone here old enough to remember editing profiles using ColorBlind Edit? Pretty good too, not close to what Kodak provided however. What toolset for editing colors to affect a profile is more powerful and well know as Photoshop? I begged Thomas Knoll often to allow us to use PS to do this, never happened.
Sounds interesting. I'd love to see that as well.
I've edited profiles in Matlab. When you load them you have access to all the internal tags including luts and curves. I've used it to modify matrix profiles but only to change gamma to one on a ProPhoto profile. I think there is a way to do this in Photoshop too. I keep intending to make a B&W printer profile. Someday.
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Eric Chan, who is now listed as second only to Thomas Knoll, on the CS6 splash screen, used to make ABW profiles for Epson 3800 and 3880 printers, until Apple decided to 'grayout' that option. Too much secret sauce.
I am old enough to think of Adobe as a font company, with a side line in a photo editing app. And then there were acquisitions.
Brian A
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Oh Andrew. Too bad you never got the hang of the Gretag tool. It really is a much better and way more professional product and let you edit the Absolute Colorimetric white points for ultra fine tuning proofing profiles for offset. The interface is perfect and super easy to understand. The old Kodak plugin, well, that's the one that's the mess and that you can only use Ps commands really limits it. I have that too but I never even think about using it. For anyone interested in serious profile editing, Gretag is really one of the only ways to go. I used to use it far more often than I do now, but I'm sure glad it's there when I need it.
For the record, Andrew has been giving the Gretag module a bad rap for years and for some reason he has not been able to grasp it. It's one of those products that once it clicks in, you wonder why you'd ever use anything else, especially for some of that hard to do stuff that nothing else can do. (and I think that Argyl has an editor but I don't know much about it, so maybe that's an alternative)
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For the record, Andrew has been giving the Gretag module a bad rap for years and for some reason he has not been able to grasp it.
One of the worst examples of a workflow and GUI ever created IMHO. If you love it, great. I'll take ColorBlind Edit which predates it by years, or better Custom Color ICC any day of the week (and both can produce the edits of Absolute Colorimetric white points).
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Eric Chan, who is now listed as second only to Thomas Knoll, on the CS6 splash screen, used to make ABW profiles for Epson 3800 and 3880 printers, until Apple decided to 'grayout' that option.
Can you explain that bit about a grayed out option?
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Can you explain that bit about a grayed out option?
Under all reccent versions of OS X, there is no way of applying a secondary profile when in ABW mode.
Brian A
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Under all reccent versions of OS X, there is no way of applying a secondary profile when in ABW mode.
Where was that? In the Epson driver/Color Handling?
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Where was that? In the Epson driver/Color Handling?
With Eric's profiles, you would set the printer for ABW mode, effectively setting the printer to manage color, then in the printing application you would set it to Photoshop (or Lightroom, etc) manages color and select Eric's profile for that specific paper. This can still be done in Windows, but on a Mac you lose the ability to set both driver and the printing app manage color. If you set Lithroom to mamage color, you cannot get to the driver's ABW mode.
http://people.csail.mit.edu/ericchan/dp/Epson3880/abwprofiles.html
Brian A
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You can work around the Apple limitation by:
1. Converting the B&W image to Eric's profile using the desired intent. This runs the RGB values through Eric's curve settings.
2. Assign the image to the sRGB profile.
Let the printer "handle color" then print it using ABW.
Eric's B&W profiles incorporate BPC across all intents but he maps AtoBn curves to their actual values which means the view proof works correctly.
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I am running Windows, so it is no prolem for me. Canon ipf accounting software is Win only, Qimage is Win only. Quickbooks used to be Win only.
Erics profiles are also only going to last the life of a 3880, then they are gone. Good while they lasted.
Brian A