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Author Topic: i1Profiler Profile Settings Sliders Investigation  (Read 6766 times)
Scott Martin
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« Reply #20 on: November 19, 2012, 09:04:28 PM »
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Scott, will there be improved quality over what I can achieve with the 16 bit plug in from Canon?

I don't think so. The plug-in is fantastic. Ever noticed that the soft proofing is better than Photoshop's?

There was also some talk about being able to control ink limiting to a very fine degree. Can I do it individually for all 12 ink channels? Would there be an advantage to the final profile quality? It would be wonderful to do that.

Sounds like StudioPrint is the RIP for you. Have fun geeking out but don't expect to get significantly better quality or anything.

I'm also wondering how critical it would be to run the internal calibration for my Canon printer. If I can control ink limiting, would it be necessary to calibrate the printer if I am not running more than one machine?

Calibration is too important to ignore, IMO. It will allow you to achieve incredible consistency over time and across head replacements.

http://canonipf.wikispaces.com/message/view/FAQ/12791457

I am also wondering if introducing a large number of grays and near grays actually improve the separation and neutrality in the grayscale.

Yes, but you don't really need that many more grays... Use i1P's patch generator and find a set that includes a ton of grays. If you increase the number of patches by one you'll see that the grays increase up to apoint where it falls back down to a minimum value. Try it - I think you'll find the intervals where there are a whole bunch of grays (like 2033).

That would take me down the road of customizing targets.

Yeah, and that's just an academic exercise, that's not likely to produce significantly better results, IMO. I have spent stupid amounts of time to make my own 16 bit i1P targets with lots of grays and a visual layout like Bill Atkinson's targets used to have. You can see the small one's at http://www.on-sight.com/downloads/  But the differences are small in comparison to what you can get by using i1P's targets at those intervals where you find a bunch of grays. I'd stick with that.

I also would like to test using 16bit targets but i1Profiler doesn't do those. Any workarounds available?

Yes but there's not much reason to do it. I actually have my own 16 bit targets and 16 bit references files that I made with the help of XRite developers. I use ColorPort to measure them and i1P to process them (which it does do in 16 bits). But there's not much difference doing it this way. If anything it allows you to get a little better quality out of fewer patches. Going forward ColorPort is hard to rely upon.
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JeffKohn
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« Reply #21 on: November 19, 2012, 09:09:08 PM »
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I'm wondering whether doing the gray optimization step after the profile has been built would be better/worse/similar compared to including all those grays with the initial target. I think Andrew advocates this quite a bit? I would really hate to run an optimization. It just adds more steps into an already complicated workflow, more paper, more ink, more drying time.
I did this (optimization) for one of my profiles, and there was significant benefit. The profile in question was originally created with a roughly 3400-patch target which had a lot of gray or near-gray patches; but when printing a test image that had a monochrome circle gradient, there was some visible banding (this particular test image is extremely unforgiving). After using the optimization step, the improvement was obvious, with the circle gradient being smooth.

There's a problem though. The optimization workflow is extremely buggy. For one thing the loading/saving of patch-sets/test-charts doesn't work well. But an even bigger problem is that the optimization workflow doesn't bother to arrange the target charts so that adjacent patches have enough difference to register as distinct patches when scanning a row at a time. The only way I've found around this is to use the "legacy charts" option with my i1Pro2, so that there are hard borders between the patches. This works fine, except for the fact that you can only scan legacy charts in M0 mode. So for profiles that you created using dual-scan for OBC, it won't work. So for the few papers I have that use the OBC workflow I can't optimize the profiles. Fortunately those particular profiles are smooth enough that it's not really an issue.

Overall I'd have to say X-Rite should really be ashamed of themselves for just how buggy this software is. Sure the profiling technology is pretty good, but the actual Windows software is just poorly written. I can't tell you how many times I've gotten errors or outright crashes when generating OBC charts, profiles, etc. If you restart the app and try again it will usually work, but that's assuming you saved what you needed to be able to resume after restarting.  The program must have memory leaks out the wazoo, not to mention bugs that cause the state of your workflow to get corrupt in various scenarios. Going back/forth through the workflow steps is particularly problematic, I've also gotten that "cannot generate white point" error message many times before.
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JeffKohn
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« Reply #22 on: November 19, 2012, 09:15:37 PM »
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The plug-in is fantastic. Ever noticed that the soft proofing is better than Photoshop's?
Do you really find the plugin's soft-proofing useful? If there were some way to get it to display full screen that would be one thing, but that tiny image preview is just too small on my 24" display. I know you can zoom in, but that just seems like an extremely tedious way to do it.
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samueljohnchia
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« Reply #23 on: November 19, 2012, 09:39:51 PM »
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I don't think so. The plug-in is fantastic. Ever noticed that the soft proofing is better than Photoshop's?
That's good to know. I had the feeling that the plug-in's softproofing seems a tad more accurate, but it doesn't offer a simulate paper white preview. I also thought that it doesn't lift the blacks as severely as Photoshop's softproofing, with simulate black ink on.

Jeff, I have no problems expanding the plug-in window to get a very large preview of the soft-proof. Well, it's quite big to me on my 27 inch display, no smaller than fitting the image to display area in Photoshop. Yeah, zooming in is annoying. I didn't even know I could do that until you pointed it out!

Calibration is too important to ignore, IMO. It will allow you to achieve incredible consistency over time and across head replacements.
Oh no, all the re-profiling to do!! Argh...

But the differences are small in comparison to what you can get by using i1P's targets at those intervals where you find a bunch of grays. I'd stick with that.
Do the custom targets produce better, smoother or more neutral profiles?
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JeffKohn
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« Reply #24 on: November 19, 2012, 10:08:48 PM »
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Jeff, I have no problems expanding the plug-in window to get a very large preview of the soft-proof. Well, it's quite big to me on my 27 inch display, no smaller than fitting the image to display area in Photoshop. Yeah, zooming in is annoying. I didn't even know I could do that until you pointed it out!
The version of the 8300 plugin I'm running on Windows has a fixed-dialog border and cannot be resized. However after reading your reply I went back to double-check this, and noticed that there _is_  a maximize button on the dialog. Never noticed that before (although I have tried resizing the window before). So while I can't resize, at least I can maximize the window. The only downside is the combo-box for selecting ICC profile doesn't expand when the dialog is maximized which means I can tell some of my profiles apart due to the way they're named.
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samueljohnchia
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« Reply #25 on: November 19, 2012, 10:51:00 PM »
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The version of the 8300 plugin I'm running on Windows has a fixed-dialog border and cannot be resized. However after reading your reply I went back to double-check this, and noticed that there _is_  a maximize button on the dialog. Never noticed that before (although I have tried resizing the window before). So while I can't resize, at least I can maximize the window. The only downside is the combo-box for selecting ICC profile doesn't expand when the dialog is maximized which means I can tell some of my profiles apart due to the way they're named.
Jeff, that is exactly how it works on my end too.
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samueljohnchia
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« Reply #26 on: November 19, 2012, 11:15:53 PM »
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Those who print in color, I hope you dig this:

Observations from Studying the Test Profiles
Saturation Slider

Introduction
I created test profiles with the following inputs for the Contrast slider, while Saturation and Neutralize Grayscale were set to 0, and Smoothness was left at the default of 50:
-50, -40, -30. -20, -10, -9, -8, -7, -6, -5, -4, -3, -2, -1, 0 , 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 20, 30, 40, 50.

I also created my own custom targets to study how well colors separate at near clipping. The target I created has a background of a color primary at clipping, that is 255 in 8 bit integer form. There are 20 small squares on the target. They run 254, 253, 252, 251 250, 249 etc. from left to right, top to bottom. The 20th square is 235. An example of the target is attached. I created separate targets for Black, White, Red, Green, Blue, Cyan, Magenta and Yellow.

Observations Notes
Gamut:
There is essentially no change to the gamut of the profile at all settings on the Saturation slider.


Tone:
Moving the Saturation slider from 0 to 1, there is a relatively significant increase in brightness in the grayscale. Everything from and including 0 - 224 brightens.

The most significant change is at RGB59. An increase of 5 values in all R,G,B channels. This is also true when moving from 0 to negative 1.

The grayscale brightness does not change much from Saturation 1 - 50. At intervals of 10, a maximum difference of 2 RGB values was noted in one or more R, G, and B channels.

However, the overall lightening jump from 0 - 1 remains. This is also true when moving from -1 to -50.


Separation of Colors Near Clipping:
   Reds
   - S40 gives the greatest separation of the positive scale, down to 250,0,0. Wierdly, lower or higher values than 40 separate less well. Reds get darker as saturation amounts increase.
   - S -40 gives the greatest separation of the entire scale, down to 254, 0, 0. Reds lighten when saturation decreases.

   Greens
   - S20 gives the greatest separation, down to 0, 251, 0. Greens turn darker and cooler when saturation amounts increase.
   - Negative saturation settings do not improve separation, and quite often makes it worse.

   Blue
   - S20 gives the greatest separation, down to 0, 0, 254. Blues also lighten significantly when saturation amounts increase.
   - negative saturation settings do not improve separation, and always makes it worse.

   Magentas
   - I can saturate up to S40 without loosing separation, down to 253, 0, 253. Magentas get darker as saturation amounts increase.
   - Magentas separate similarly well at negative saturation settings. Magentas get lighter as saturation amounts decrease.

   Yellows
   - I can saturate up to S50 without loosing separation, down to 253, 253, 0. Yellows get darker as saturation amounts increase.
   - S -20 gives the best separation of the entire scale, down to 254, 254, 0. Yellows lighten as saturation amounts decrease. Max yellow (255, 255, 0) becomes unnaturally light for negative saturation then. This effect is very very ugly.

   Cyans
   - I can saturate up to S20 without loosing separation, down to 0, 251, 251. Cyans get darker as saturation amounts increase.
   - S negative 30 gives the the greatest separation of the entire scale, down to 0, 253, 253.
   - Max Cyan becomes unnaturally light for negative saturation. This effect is ugly, but not as bad as yellow.

Preliminary Conclusions
Choosing the optimal Saturation slider amount requires one to know what colors are the most important to one. Settings that are optimal for one color primary can produce results that are quite horrible for another. Generally speaking, I do not like the visual effect of negative saturation amounts, especially for the yellows. One can still retain very good separation at positive amounts of the saturation slider, for all the color primaries listed above. Red may be an exception.
« Last Edit: November 19, 2012, 11:19:04 PM by samueljohnchia » Logged
samueljohnchia
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« Reply #27 on: November 20, 2012, 12:40:24 AM »
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Observations from Studying the Test Profiles
Neutralize Grayscale Slider

Introduction
I created test profiles with the following inputs for the Neutralize Grayscale slider, while Contrast and Saturation were set to 0, and Smoothness was left at the default of 50:
0 , 1, 2, 3, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100


Observations Notes
Gamut:
There is essentially no change to the gamut of the profile at all settings on the Neutralize Grayscale slider.


Tone:
Moving the Neutralize Grayscale slider from 0 to 1, there is a relatively significant increase in brightness in the grayscale. Everything from and INCLUDING 0 - 224 brightens.

The most significant change is at RGB59. An increase of 5 values in all R,G,B channels. This is also true when moving from 0 to negative 1.

The grayscale brightness does not change much from Neutralize Grayscale 1 - 100. Often, no change is noted.


Color Changes:
Comparing 1 and 100, a difference of 1 RGB value was noted in the blue channel, for every value above 93, just below middle gray (100) for ProPhoto RGB, based on the L* curve.

Comparing 10 and 100, a difference of 1 RGB value was noted in the blue channel, for every value above 100, exactly at middle gray for ProPhoto RGB, based on the L* curve.

Preliminary Conclusions
The paper that I printed on is Harman by Hahnemuhle Gloss Baryta, which has moderate amounts of OBAs in the paper base. Ethan has noted that the slider has more effect on papers containing lots of OBAs or when using "older tungsten-illuminated instruments (i1Pro, iCColor, Spectrolino)". I do not use papers with very high OBA content, so I cannot comment on that situation. The discussion in that thread does make logical sense though.

I must move the Neutralize Grayscale slider from 1 all the way to 80 before I can detect a difference in 8 bit integer precision. In 16 bit precision, there is a small difference at every increment in the slider, but no one should be able to notice the increment visually. The single greatest difference is going from 0 to 1, a huge brightness increase.

The Neutralize Grayscale slider also affects colors, with up to 4 values in difference in the blue channel, less in the red and green. Increasing blue is logical, to neutralise the otherwise too-warm interpretation of the profile, when a UV-cut measurement is not made. The colors that are affected the most are the dark yellows and greens.
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JeffKohn
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« Reply #28 on: November 20, 2012, 12:44:55 AM »
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I wonder how the Neutralize Gray slider interacts with the OBC module, but I suspect figuring that out might be difficult.
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samueljohnchia
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« Reply #29 on: November 20, 2012, 01:41:24 AM »
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I wonder how the Neutralize Gray slider interacts with the OBC module, but I suspect figuring that out might be difficult.

No Jeff, it is not difficult. I just ran some more profiles to investigate that. I'll appreciate it too if you could run these tests on your favourite printer+paper combination, and let us know if you observe something similar.

Regarding OBC profiling, the Neutralize Grayscale behaves similarly, except that the big brightness jump from 0 to 1 is not present. I still get a change of up to 2 values in one or more R, G, and B channels. Don't know why.

I'm guessing that if one picks patches from the OBC test chart that result in non-neutral grays when building the profile, the neutralize gray slider will still have visible effect. I'm not sure if i1Profiler is looking at the AtoB or BtoA perceptual table (possibly both) to figure if a gray is neutral or not. It may be looking at lab values for all I can tell. If grays are already very neutral to begin with, then it has much less of an effect. That's all I can tell now.
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digitaldog
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« Reply #30 on: November 20, 2012, 10:03:26 AM »
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On the Epson printers I have (3880, 4900), using a custom 1728 patch target from i1P, I do see a slight  benefit to the 2500 patch gray optimization. It only kicks in with Perceptual and it's subtle. But if you have an iSis like I do, it's worth the time (media, that's your call). And so far, no customers who've had optimization have indicated anything worse than the optimized profile seemed to output like the original. No harm done.

You have to proceed in the proper order here if you also want to use OBC module. You'd do OBC then Optimization. Can't Optimize then do OBC (why I don't know). OBC is pretty slick and useful. But you tie the profile to one viewing condition. The visual based system works pretty well (we need more of this. I'd love to see the Macbeth used more in this product, the current implementation is really half baked).

All these sliders for profile creation and at least for me, when soft proofing, I pick RelCol 9 times out of 10.
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Andrew Rodney
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« Reply #31 on: November 20, 2012, 10:05:45 AM »
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I wonder how the Neutralize Gray slider interacts with the OBC module, but I suspect figuring that out might be difficult.

If this is supposed to be something like we had in ProfileMaker Pro, it's supposed to account for very non white (neutral) papers. Like newspaper stock. I'd suspect OBC would be another process that may or may not be necessary,
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Andrew Rodney
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JeffKohn
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« Reply #32 on: November 20, 2012, 12:51:39 PM »
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All these sliders for profile creation and at least for me, when soft proofing, I pick RelCol 9 times out of 10.
For fiber-gloss papers, so do I. So far I haven't found any combination of settings for which the perceptual rendering doesn't change the contrast of the image, which I don't like. With the Contrast slider set anywhere from 0 or higher, the bottom half of the tonal range gets at least slightly darkened, while negative Contrast slider values avoid this but have the effect of flattening the upper tones. It's really strange because in PMP/i1Match the perceptual rendering always lightened the image.

Matte papers are different though. Rel-col will almost always cause too much detail loss in the darker areas. And given the tonal compression needed to fit the more limited gamut/dmax of matte papers, the perceptual rendering doesn't increase contrast and the lower tones don't get darkened. I almost always end up preferring perceptual intent for matte papers.
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« Reply #33 on: November 20, 2012, 02:03:26 PM »
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...
Exciting to see you do this. Exhaustive testing like this is what separates the pros from the rest.

well this comment immediately followed mine, where I stated my patience for flushing out every interface aspect and troubleshooting problems had waned. Exhaustive testing is done here all the time, and was and is still done for this software. But it is prioritized to the issues most likely to the most significantly effect results in the prints. I confess I did not do all 14.4 billion setting combination tests, perhaps the real pros here did.
I would not advise others to go down the n channel, RIP, path as I have, you will encounter even more problems with the software to flush out on your own, not to mention entirely new issues leapfrogged by the RGB workflow. I'd only advise it if you are ready for a significant learning curve to take over your life for a while, little good advice from anyone else, and have very real printing challenges that can be addressed only by diverting from the RGB workflow. This includes many things we take for granted, like the tools we all use for gamut volume info, etc.. new questions even there in n channel...
Again, I appreciate your testing, and sharing your results.
Tyler
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samueljohnchia
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« Reply #34 on: November 21, 2012, 02:37:24 AM »
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On the Epson printers I have (3880, 4900), using a custom 1728 patch target from i1P, I do see a slight  benefit to the 2500 patch gray optimization. It only kicks in with Perceptual and it's subtle. But if you have an iSis like I do, it's worth the time (media, that's your call). And so far, no customers who've had optimization have indicated anything worse than the optimized profile seemed to output like the original. No harm done.

You have to proceed in the proper order here if you also want to use OBC module. You'd do OBC then Optimization. Can't Optimize then do OBC (why I don't know). OBC is pretty slick and useful. But you tie the profile to one viewing condition. The visual based system works pretty well (we need more of this. I'd love to see the Macbeth used more in this product, the current implementation is really half baked).

All these sliders for profile creation and at least for me, when soft proofing, I pick RelCol 9 times out of 10.
Andrew, I do not have an ISis. I use an i1 Pro 2, so scanning increasing amounts of patches really add up. I don't do remote profiling or many printer+paper combinations, so I don't really need any automation yet. I'll test the Optimization process in the near future.

I also tend to find that an OBC-ed profile tends to end up with the grayscale looking very blue. The more OBAs present, the bluer the grayscale appears in the soft proof. It isn't really what prints out though. About tying it to one viewing condition - lots of prints have to be viewed in changing/different lighting conditions. Do you find OBC useful in those situations?
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digitaldog
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« Reply #35 on: November 21, 2012, 08:47:13 AM »
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The more OBAs present, the bluer the grayscale appears in the soft proof. It isn't really what prints out though.

If the soft proof doesn't sync up after OBC, then it sounds like a bug or issue with the preview portion of the profile. Do you see any visual difference in a soft proof from identical profiles where the ONLY difference was OBC correction?
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Andrew Rodney
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samueljohnchia
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« Reply #36 on: November 21, 2012, 01:08:41 PM »
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If the soft proof doesn't sync up after OBC, then it sounds like a bug or issue with the preview portion of the profile. Do you see any visual difference in a soft proof from identical profiles where the ONLY difference was OBC correction?

My words may have sounded too harsh. The differences are subtle.

There ARE visual differences in a soft proof from identical profiles were the only difference was OBC correction. Obviously, this is to correct for the overly yellow profile, which was compensating for the too-blue-to-the-software+spectro effect. I want to see differences, otherwise I would think OBC is not working.

The blue-shift difference is less in the print I suspect because of visual constancy. My eyes are compensating to neutralize what I *think* are neutrals.

The relative difference is bit like seeing the blacks go all gray and flat when softproofing a matte print with black ink simulation- none of the matte prints I make ever print out that flat in real life. Sometimes, they can even seem denser than glossy blacks, because of surface reflections.
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digitaldog
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« Reply #37 on: November 21, 2012, 02:11:37 PM »
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Maybe the A to B table(s) need some work after OBC? Not that we have a tool for that in the package.
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Andrew Rodney
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samueljohnchia
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« Reply #38 on: November 24, 2012, 11:03:25 PM »
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In response to the comments above about improvements after optimizing profiles in i1Profiler, I attempted my own investigations.

Introduction

There has been some discussions going on the luminous-landscape and other forums about optimizing profiles in i1Profiler. The general view is that if one starts out with a large number of patches for building the initial profile, say around 2000 patches, then the optimization routine does not show much fruit. This is true for when the optimizing patches are generated automatically by the “Smart patch generator”. Andrew Rodney noted that the maximum differences were less than 1 deltaE. That is hardly any difference. However, Andrew and others have seen a marked increase in gray neutrality and smoothness when using the 2502 spot grays optimization file and process detailed here: http://www.i1upgrades.com/2011/08/how-to-use-the-tc-2502-gray-optimization-chart/.

I want to test whether optimizing a profile with patches generated by the smart patch generator result in any improvement. I also want to test whether optimizing with the custom 2502 spot grays will result in any improvement. I tested this on two profiles, which I will call "Profile A" and "Profile B" for simplicity.

Both profiles were built from targets containing over 3000 patches, but less than 4000 patches. Both targets contained a significant number of neutrals, more than 329 neutrals and near-neutrals, which is the maximum number that i1Profiler can generate automatically.


Test Results

Optimizing Profile A with 2502 grays

Grays
•   After optimization, grays became noticably cooler, especially in the highlights. Smoothness was slightly but visibly improved.
•   There was a maximum increase of 5 values in the blue channel (the maximum increase occurred from RGB114 to 122), and a max value of only 4 in the R or G channels. This explains the cooler grays.
•   There was also slightly improved separation in the dark grays, close to black, in the RGB 0 to 60 range)

Colors
•   After optimization, there was a noticeable but slight increase in separation in the blues near clipping (Blues 235 to 255).
•   After optimization, there was huge separation loss in the yellows near clipping (Yellows 240 to 250)

Optimizing the Profile B with 1260 patches generated by the “Smart patch generator”

I generated a 1260 patch chart using the “Smart patch generator”, which happen to contain a number of colors and a fair proportion of neutrals and near-neutrals, in a ratio of about 2 part colors, 1 part neutrals.

The optimized profile has a gamut volume of 766 217, calculated by ColorThink Pro.
The original profile has a gamut volume of 768 465, calculated by ColorThink Pro.

Grays
•   Gray values hardly changed. A maximum increase of 2 values in the blue channel and a maximum change of  only 1 value in the R or G channels was noted.
•   Grays did not seem to get lighter or darker.
•   Grayscale did not become smoother.

Colors
•   Magentas were the most severely affected. It appears that i1Profiler attempted to correct the magentas to give a smoother result, but a large portion of it was lightened, and a small but visible transition to the darker shades appeared. This is arguably a worse result.
•   Dark Oranges and greens appear to be slightly smoother, but the difference is so slight I can barely make it out in the softproof. Only by converting a granger rainbow to the original and optimized profiles and comparing them as two layers in a non-color managed Photoshop document using the difference blend mode, did I first notice this difference.
•   There was huge separation loss of the yellows near clipping (Yellows 235 to 255) after optimization.
•   Blue separation was very good to begin with, so optimization did nothing to improve it.

Optimizing Profile B with 2502 grays

Optimization failed. X-rite said that there was an error creating profile, despite me making 4 different measurement scans, and multiples tries rebooting the computer, and re-launching i1Profiler. I suspect that the memory limit on i1Profiler was reached, because of too many patches in total (3256+2502 patches). I get the same error after I have asked i1Profiler to generate about 8 large-patch profiles, and I have to re-launch the application to clear the memory.


Preliminary Conclusions

The Profile B did contain a fair bit more spot gray patches than Profile A. This resulted in a profile, which before optimization, that is already far smoother than any of the i1Profiler-automatically-generated-patches-based profiles I have created, and is even smoother than Profile A after optimization with 2502 grays. This is outstanding performance.

It seems, to my way of thinking, that selecting optimal patches for profiling does result in a superior final profile, and having a superior profile is better than trying to optimize a sub-optimal profile. More on optimal printer targets later.

I wish to make it clear that Profile A already has a pretty smooth grayscale gradient with almost no banding to begin with, and it is as smooth as the i1Profiler 5837 patch profile. The additional smoothness I see from either the optimization process or the superior custom target is subtle, but visible.

This investigation also informs me that the optimization that i1Profiler does is detrimental to the separation of high saturation yellows, a color which I find for my Canon iPF8100, is very hard to separate to begin with. I am also not happy with the way it dealt with the magentas.

Getting a smoother grayscale with Profile B took far less time, ink and paper, and produced a smoother grayscale than Profile A after optimization.

All in all, I have to say that an optimized version of an already very good printer profile, is worse than the original profile.

An optimized version of a suboptimal profile probably will result in an improvement, but I do not think creating a suboptimal profile to begin with is a good idea. I also question whether the gains of optimization, at the cost of additional ink, paper and time, is worth it.
« Last Edit: November 24, 2012, 11:06:12 PM by samueljohnchia » Logged
samueljohnchia
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« Reply #39 on: November 24, 2012, 11:27:19 PM »
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All these sliders for profile creation and at least for me, when soft proofing, I pick RelCol 9 times out of 10.

There has been some research that when using the relative colormetric intent, with Adobe's black point compensation turned on, colors are shifted in hue and saturation more than they would, compared to the perceptual rendering intent. Other research that I have read, including Adobe's technical article on the implementation of black point compensation, also indicate that even the lighter colors (up to density 0.5 or so) are also affected.

Basically, black point compensation turned on results in less accurate colors in terms of hue and saturation.

So far I haven't found any combination of settings for which the perceptual rendering doesn't change the contrast of the image, which I don't like. With the Contrast slider set anywhere from 0 or higher, the bottom half of the tonal range gets at least slightly darkened, while negative Contrast slider values avoid this but have the effect of flattening the upper tones. It's really strange because in PMP/i1Match the perceptual rendering always lightened the image.

I haven't noticed this loss of separation in the dark values with the perceptual rendering intent, when using a well-made profile. Actually I have found that rel col with BPC results in a grayscale that is less smooth, and less like the original tonality of the synthetic target. With the contrast slider of i1Profiler set to 0, There is no darkening of the low values, as I have discovered with additional testing. This was not mentioned in my previous post about the Contrast slider. Moreover, the printing gamut of perceptual is larger than rel col for i1Profiler's profiles.

Scott has been saying for some time now that Monaco Profiler, and now i1Profiler, is to be noted for simply outstanding perceptual output. But lots of folks think that perceptual compresses in gamut colors too much, and so resort to printing with rel col. If you are printing scientific or technical images with fairly light colors and no shadows of any sort, I wouldn't hesitate to print with relative colormetic, without black point compensation on. If you are printing images with highly saturated color, with important shadow information, I think perceptual may be a better option.

Scott, I would greatly appreciate your input and advice on the advantages of printing with perceptual, when one has a good quality printer profile.
« Last Edit: November 25, 2012, 12:13:13 AM by samueljohnchia » Logged
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