i1Profiler Profile Settings Sliders Investigation

[samueljohnchia]

These are my notes from a small experiment to investigate the properties of profiles that i1Profiler creates. It's going to be a bit long, as I continue to update this thread with further investigation.

Nobody tells us exactly what these sliders do. What exactly do they change? What are the downsides to these changes? Do we have to sacrifice some gamut for more smoothing, or maybe a higher dmax for a neutral grayscale? Under what circumstances are the changes useful? When are they irrelevant? Are there optimal values and suboptimal values for each slider? (That is, say never set the smoothness slider at XX value because the profile’s printing gamut suddenly becomes all wonky from a bug.) Do certain combinations of slider settings do things that are undesirable, hurt the profile quality, or maybe improve things beyond your wildest imagination?

I would like to clarify that I am not a color expert, or mathematician or scientist or the sort, so if anyone spots an issue that is technically flawed, I will be very happy to retract my statements, and I will re-investigate that aspect again.

Introduction
Andrew Rodney, in a review of the i1Profiler software on the luminous landscape website, stated that “many of the provided sliders [in the "Profile Settings" module] produce tiny, almost insignificant differences from each end of the slider scale”. “Building profiles with both extremes for the Smoothness slider produced results that were less than a max deltaE of 1”. With all due respect to Andrew, I believe him.

I am curious if I can see a difference between various settings of the sliders when building RGB printer profiles. I made a series of profiles, from a measurement file I scanned from a target I printed, with varying inputs of the following sliders found in the “Profile Settings” module: Contrast, Saturation, Neutralize gray, and Smoothness. These sliders affect the rendering of the perceptual table of the printer profile. I am using i1Profiler version 1.3.2.

These settings remain constant for all the test profiles I generated. For "Tables", “Size A to B” is set to “Large”, “Size B to A” is set to “Large”, and “Granularity” is set to “16 bit”. Under "Advanced", “Chromatic Adaptation” is left at “Bradford”, a pointless setting since my illuminant used in the “Lighting” module is D50. ICC profile version is Version 2, and “Profile White point” is “Default”.

How I Made my Observations
Be aware that many of the following observations are SUBTLE. One method I use to better see the difference is to convert a granger rainbow with a sidebar neutral grayscale target (so I can see the effect on grays too) to various test profiles, layer the results in a non-color managed document, and use the difference blend mode and a strong curve adjustment to see where changes have occurred. An example of the target is attached.

I also use the ‘flash to compare’ method, where I create a custom proof setup for a test profile, and then change the proof settings to another test profile. Checking and un-checking the ‘preview’ checkbox ‘flashes’ the view. One method to judge the gamut of the profile would be to activate the gamut warning overlay together with a proof setup using the profile in question on a granger target in ProPhoto RGB color space. This is done in Photoshop.

I have looked at the Smoothness thus far, and will work on the others soon.

Observations from Studying the Test Profiles
Smoothness Slider

I created test profiles with the following inputs for the Smoothness slider, while Contrast, Saturation and Neutralize Grayscale were set to 0:
0, 10, 20, 30, 40, 50, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 90, 100.
 
When the “Smoothness” slider is set to zero, the resultant printer profile has the largest gamut. When it is set to 100, the gamut is much smaller. I do not know why the gamut has to shrink, but at this point, to my mind, one has to sacrifice gamut for smoothness. But it’s not so simple, more on that later.

Comparing 0 and 100, the profile with smoothing at 100 is visibly smoother mostly in the light yellow-green (I’m thinking sunlit grass, foilage) color areas. Reds are also visibly smoothed across most of the range. Oranges are affected to a lesser degree. Blues were somewhat smoother, mostly in the darker regions, but it's the most subtle change.

Looking at the gamut, in intervals of 10, it shrinks from 0 to 10, 10 to 20  and 20 to 30, but increases from 30 to 40 and 40 to 50 (but less so), then decreases from 50 to 60 (60 being smaller than 30), and continues to do so for 70, 80, 90 and 100. Still it is not so simple. Look at settings spaced 1 value apart.

It is interesting to note at this point that there are no changes to neutral gray tones until the smoothing slider hits 61. They remain unchanged at 0, 10, 20, 30, 40, 50 and 60. I didn’t try out settings in between those values, but I’m assuming that they do not change then too.

Smoothing Slider from 60 - 70
Ok, so the gray values are the same until 60. At 61, they lighten. It is mostly seen in the middle regions of the grayscale. From 62 to 63, they do NOT change at all, when compared to 61. Very interesting. Grays get darker going to 64, and lighter at 65. 64 compared to 60 is almost the same, with a 1 value change in one R, G or B channel only. From 66 to 69, gray values are almost the same as 65, with a 1 value change in one R, G or B channel only. Gray values lighten at 70. When I say 1 value change in one R, G or B channel only, I mean something like R130 G128 B126 changes to R130 G129 B126.

The profile gamut increased from 60 to 61, decreased going to 62 (62 almost identical to 60), increased at 63 (bigger than 61), decreased at 64, increased at 65 (bigger than 61 and 63), and decreased gradually from 66 to 67, 68, 69 and 70.

Smoothing Slider from 70 - 80
Gray tones get lighter from 70 to 71. From 71 to 79, increasing smoothing by a value of 1 resulted in minimal changes to grays. No more general lightening or darkening. Most grays do not change. Those that do exhibit a 1 value change in one R, G or B channel only.

Profile gamut increases from 70 to 71 (note that 71 gamut is greater than 61), decreased at 72 (72 slightly smaller than 70), decreased at 73 (by a very small amount), increased at 74 (very slightly too; 74 only slightly larger than 72), increased at 75, and more or less decreased (tiny differences) from 75 to 76, 77, 78 79 and 80.

Note that the gamut of the profile when Smoothness is set to 71 is larger than when it is at 61. So the assumption that gamut gets smaller when increasing the smoothing amount is not always true. Sometimes it increases. But 100 is much smaller than 0.

This is very very interesting behavior to me.

[Rhossydd]

I'm interested in the effects of the sliders too.
To clarify what methods you're using;
How are you determining how gamut is changing ? As I understand it the tools in Photoshop aren't ideal for this and a profile inspection tool would be a more appropriate choice. It would also allow you to put some hard numbers to the investigation.

Later;
I've just spent a small time confirming your results with respect to gamut volume;
Setting the same as above using a 2033 patch set sample from an Epson 3800 on gloss media measured with an i1Pro.
Gamut volumes reported by Gamutvision
Smoothness slider setting > volume
0----888453
60---888453
61---806826
62---806801
63---888453
64---806351
65---806346
100--769910

These pretty much trend with your observations above.

Looking at the 3D gamut plots; It seems to be an overall shrinkage of gamut, with just the extreme very dark blue colour range being slightly more reduced than other areas.

Original reply edited to provide additional information.

[samueljohnchia]

Rhossydd, I assessed the gamut by looking at how many colors in a ProPhoto RGB granger rainbow target get clipped, indicated by the gamut warning overlay together with the profile loaded in view>proof setup>custom. This is done in Photoshop. I know it is not ideal. I do not have Gamutvision. I borrowed a friend's Colorthink Pro software and it thinks all the profiles have the same gamut volume, in the "Profile Inspector" module. Clearly they are not. Perhaps I don't know how to use Colorthink properly.

One thing about gamut volume numbers is that two profiles can have very similar gamut volumes, but may not include the same region of colors in gamut. Plotting them together in 3D will help us see where they overlap. That's where your software would be very revealing. Looking at the numbers alone won't tell the whole story.

I see that your profile at 0 and 60 are identical in volume. My profile created with smoothness at 60, clips a lot more colors than when at 0. Your results from 61 onward are similar to mine in that the gamut increases and decreases as the smoothing amount increases. It is not predictable.

It is very interesting to see it grow and shrink by a reasonable amount even with an increment of only one value. Looking at your gamut volume numbers, a simplistic conclusion could be if you have the smoothness slider at 65, setting it to 63 is a better idea. This is very very weird stuff to me.

[digitaldog]

We really want to view the gamut using ColorThink Pro. (http://www.colorwiki.com/wiki/Color_Management_Myths_26-28#Myth_26)

If memory serves, the settings only apply when using the Perceptual table. There have been a number of dot releases since my initial testing of some of the sliders.

The tests here seem to agree with my idea that a 0-100 scale (instead of 0-10) is X-rite just not thinking logical GUI design! The slider granularity currently used is just not necessary.

[samueljohnchia]

Hi Andrew, thank you for your input. I mentioned in the first post, I too think the sliders only affect the perceptual tables, not the colormetric or saturation tables. If someone knows otherwise, please correct me.

Graphing the profiles in 3D in Colorthink Pro agrees with my initial observations using gamut warning in Photoshop. It can be a little difficult when two profiles are barely larger than one another in gamut, to see where they differ. Would you like to have the profiles to take a look at them yourself? Not sure how the EULA applies here.

What I am thinking now is that the slider is not behaving predictably in small increments. Perhaps larger incremental amounts in its scale would be more logical. But given this kind of results, how would one choose an ideal setting for the smoothness slider? For example, gray values (equal R, G, B value combinations) do not get affected up to 60. At 61, they lighten visibly. Is this lightening better? More linear? More pleasing? I don't know. But hey, it darkens again at 64, and lighten again at 65. These are visible jumps in the gray tones, not the almost invisible jumps from 71 to 79. I am confused. Do I need more gamut or more smoothness? Sometimes I get both! Sometimes no. How do I determine the optimal slider position?

What happens with a different printer+paper combination?

[digitaldog]

At some point, you make a few profiles with the radically opposite settings, print a few images and then get the idea that these 'tools' provided are kind of silly as designed and delivered. That you roll one or two custom settings (as assets) and move on. A lot of the tools are marketing generated and of questionable usefulness. And yet do we have a tool here to edit the white point of a printer profile?

[JeffKohn]

And yet do we have a tool here to edit the white point of a printer profile?

Latest version of i1Profiler lets you override the white point when generating a profile, if that's what you mean. Speaking of which, any idea why i1Profiler often gets the white point wrong for some papers? For instance I can measure a paper white of L* = 94 but i1Profiler will use L* = 92 by default. Does it have a good reason for doing this? Will it be to the benefit or detriment of my profile if I override and use the actual paper white value?

[samueljohnchia]

Andrew, what do you mean by "And yet do we have a tool here to edit the white point of a printer profile? "? Jeff pointed out that the latest version of i1Profiler allows a user to manually choose a white point. How is this useful for a critical user?

Jeff, thank you for pointing out this white point bug. I have yet to notice it, but I will pay close attention, since I am generating many many profiles, from various paper combinations. Just something weird I discovered early on, if I am generating profiles using the same measurement data, but with different "Profile Settings", I have to reload the measurement file data again in the "Measurement" module, otherwise i1Profiler will give me an error message saying that there is no available white point. This sounds stupid to me. How could it have 'lost' the white point?

[digitaldog]

I want to edit the white point after I build any profile (in some cases usually for CMYK cross simulations).

[samueljohnchia]

I want to edit the white point after I build any profile (in some cases usually for CMYK cross simulations).

Ah, thank you, Andrew. There is still a lot I don't know about, since I do not have experience with press printing, HP indigos, and digital lab photo finishing printers. I basically only have direct experience with pigment inkjet prints, so I never appreciated the need for that. But can't you take the profile made by i1Profiler and run it through PM5 to edit it?

I'm testing the contrast slider next, will update later.

[samueljohnchia]

Observations from Studying the Test Profiles
Contrast 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, 0 , 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 20, 30, 40, 50.

I chose to evaluate profiles created at those settings because the visible difference in results seemed most linear or obvious at those settings, except for when the slider was less than 0. I do not like the visual effect when softproofing profiles build with Contrast less than zero. The rendering of tones appear unnatural to me - the tonal range is flattened too much. Jumps of 10 in the negative direction produced visibly different results at every interval, if you are interested. I just didn't bother to look deeper. Too many things!

The exception is that the jump from 0 to 1 is relatively huge, and quite visible, up to a change of 4 values (getting darker) in all RGB channels. It is the single most significant change throughout the slider in the positive range. I find this quite unusual.

The change from 0 to 1 is about 400% larger than going from say 10 to 20, or 30 to 40. The difference of going from 0 to 1 is the same as going from 10 to 50. I do not suggest finessing the sliders between intervals of 10 when above 10 (I know, that sounds confusing). The differences are too small. However, finessing the sliders between 0 and 10 give about the same difference as say going from 10 to 20. So it looks like the granularity of the slider may be needed at near zero levels, almost like logarithmic behavior?

Observations Notes
Gamut
There is essentially no gamut change throughout the range of the slider.

From 0 - 1, there is a very very very slight loss of gamut in the dark greens. (less than the increase of in the light aquas)
From 7 to 8, there is a very very slight increase in gamut in the light aquas.
This additional clipping is so slight I cannot see it in 3D in colorthink. But the gamut warning in Photoshop indicates additional clipping. I am not familiar about the precision of the gamut warning in PS, so it may be wrong.
When I built profiles from a different printer+paper combination, and changing Contrast does not change the gamut at all.

Tone
The difference in tonal rendering from Contrast 0 to 1 is huge compared to going from 1 to 2, 3, 4, 5, 6, 7, 8, 9 and 10.

9 to 10 has a slightly less visible jump in contrast, where there is a less than 1 value increase in one or more R, G or B channels, in 8 bit terms. A 16bit/color channel target will indicate with greater precision where and what the differences are.

When I mention "RGB values", I was looking at gray values with equal amounts of R, G, and B. Bear in mind that other color combinations also experience change. I just looked at the grayscale for simplicity.

From 0 to one, RGB16 to RGB18 do not change in brightness. RGB values from 15 to 1 get darker. Values close to zero experience a 1 value change in one R, G or B channel only. Everything from 19 to 253 gets lighter. Values close to white experience a 1 value change in one R, G or B channel only. Note that the lightening and darkening here is very visible, not subtle. The maximum change is 4 values (darker) in all RGB channels.

When increasing Contrast slider amounts from 10 to 20, 20 to 30, 30 to 40 and 40 to 50, RGB values 236 to 255, 100 to 102, and 0 to 14 remain unchanged. From RGB103 to 235, grays lighten. from 15 to 99 they darken.

This makes sense as the RGB middle gray value of ProPhoto RGB based on the L* curve is about 100, 100, 100. It is interesting to note that the cut-off for the highlights is 20 values under 255, and shadows is 15 values above 0. I suspect greater highlight protection in the near white regions is employed because current inkjet printers show greater separation in highlight detail than in shadow detail. Flattening that extra information may not be desirable. This is my assumption only.

The maximum change is only 1 value in one or more R, G or B channels when going from 1>2>3>4>5>6>7>8>9>10>20>30>40>50.

I have not decided yet if leaving the contrast slider at 0 instead of at any other value is the most ideal setting. But I may just do so.

[digitaldog]

But can't you take the profile made by i1Profiler and run it through PM5 to edit it?

Not unless I boot into 10.6 or whatever was the last OS version that editor would run. Plus that editor really kind of sucks eggs IMHO. Lastly, where's the new editor or editing tools for the newer i1P package? Don't hold your breath. The pace of software development at this company is incredibly slow.

IF I were going to have to edit a profile, boot into an older OS to do so, I'd probably just go back to an older version of Photoshop and use the old and pretty awesome Kodak Custom Color profile editor (or boot OS9 or there about and have at it with ColorBlind Edit).

But the other point I'll make is that while it would be so great to have an effective, somewhat easy (OK just intuitive) profile editor, there are a few simple areas we just need some simple tools to take an existing profile and edit the back and white point of the profile.

[digitaldog]

The exception is that the jump from 0 to 1 is relatively huge, and quite visible, up to a change of 4 values (getting darker) in all RGB channels. It is the single most significant change throughout the slider in the positive range. I find this quite unusual.

I have not decided yet if leaving the contrast slider at 0 instead of at any other value is the most ideal setting. But I may just do so.

Thanks for taking what has to be a lot of time testing here. But I suspect what you might find is that there is really no logic behind the settings. At least what you report backs up what I suspected a very long time ago when I worked with the early product and came to the conclusion that the settings don't appear to be understood by those who coded them, let alone us users. 

I use a setting of 40 contrast. Why? Well initially I set the Colorful preset/default if you will, that's were contrast stuck.

The other thing I'll suggest to any i1P user. IF a new version comes out, take some measurement data you saved and build the profile as you did in the past. Don't necessarily expect that drag and drop of an older profile will update all the workflows correctly. Test to see if anything new in the dot release caused a change compared to the older profile. Unless we are specifically told by X-rite that something in a new build affects the engine, don't assume it doesn't! Trust by verify.

[samueljohnchia]

Thanks for taking what has to be a lot of time testing here. But I suspect what you might find is that there is really no logic behind the settings. At least what you report backs up what I suspected a very long time ago when I worked with the early product and came to the conclusion that the settings don't appear to be understood by those who coded them, let alone us users. 

Andrew, you are welcome. I'm just trying to gain some additional knowledge about what *I think* the sliders do. It's been rather quiet of late around the forums here. I remember some time back there were hot discussions about working spaces and all that. The fad seems to have died. I hope others will join in to help/verify what's going on their end. I would be grateful if Scott Martin, who is a great advocate of the quality of the i1Profiler profiling engine, could comment on his findings. I'm sure he'd had discovered this a long time ago. I also know that Tyler Boley of Custom-Digital has also done some extreme testing and experimentation, even hacks, to achieve results that few of us ever can. If you are reading this, please share your findings.

I use a setting of 40 contrast. Why? Well initially I set the Colorful preset/default if you will, that's were contrast stuck.

I see less separation in the shadows with the contrast slider at 40 compared to 0. I may not use it at that value for my final profiles, but it is a subtle difference. Interestingly, above 0, the rest of the grayscale gets lightened, and seems to better match the tonality of the original synthetic grayscale. Of course your setup and requirements are different from mine and I am sure your profiles are excellent.

Whatever it is, it seems that setting the sliders at factors of 10 is fairly predictable. Incremental changes of 1 unit seem to produce highly unpredictable results, especially around the default value for that slider.
Default values for Contrast is 0, Saturation - 0, Neutralize Grayscale - 50 and Smoothness - 50.

Please, if anyone else out there also has i1Profiler, and can spare the time, it would be wonderful if you can verify these observations.

[TylerB]

I have to admit I ran out of time and enthusiasm for this endless testing to find answers the people who coded the software should be able to provide. Also some support issues I worked on with them simply never got any attention. I'm very happy with the profiles, for the most part, the software creates. One question to complicate your tests...
Do these differences in settings results carry through when that same profile has been optimized? Optimization has proved absolutely necessary for it's CMYKOG profiles.
I'd love to dive back into this, and I'm happy to see your work, other things have taken priority lately.
Tyler

[Scott Martin]

I'm hesitant to spend too much time going into all the specifics this week as I'm traveling but let me say that, as to the Perceptual rendering settings, I think it's important to separate color management from color correction, and therefore I try to find the settings that produce what I consider to be the best conversion that visually preserves the original image without "correcting" or "enhancing" it. With this in mind, I feel that the contrast setting is more of a subjective "enhancement" control as opposed to a valuable color space conversion adjustment. Make sense? There are surely uses for it but I doubt I'll ever use it. It's quite rare that it makes sense to combine color corrections with color space conversions.

The saturation slider is fantastic - it's one of the crown jewel technologies acquired from Monaco. The way it works is brilliant. Increasing saturation here doesn't effect or over-saturate what I like to call "mid-gamut" colors like skin tones. Instead, it controls the "edge gamut" colors. Think about super red saturated fall leaves and all the delicate veins and texture within the leaf. Use a low setting and the edge gamut colors are less saturated but full detail is present. Use a high setting and the edge gamut colors are much more saturated at the sacrifice of tonal detail. I think there's a sweet spot that gives the best of both worlds. But I won't spoil the movie - why don't you do your own testing and let's compare notes. :-] Same with Neutralize Gray.

Exciting to see you do this. Exhaustive testing like this is what separates the pros from the rest.

[samueljohnchia]

I have to admit I ran out of time and enthusiasm for this endless testing to find answers the people who coded the software should be able to provide. Also some support issues I worked on with them simply never got any attention. I'm very happy with the profiles, for the most part, the software creates. One question to complicate your tests...
Do these differences in settings results carry through when that same profile has been optimized? Optimization has proved absolutely necessary for it's CMYKOG profiles.
I'd love to dive back into this, and I'm happy to see your work, other things have taken priority lately.
Tyler

Tyler, I empathize with you. Nobody should have to test all the sliders at individual single unit increments. It is a pain in the ass to run through hundreds and thousands of profiles. The total number of combinations on the "Profile Settings" module is 14.4 billion, not including the variety of ways one can set the white point. If you include that, it is 9.2390544 Quintillion, or 9.2390544 billion billion. Seriously, that's not even including the optimization step.

I saw an early indication that using the sliders in combination can give unexpected results. This would be very painful to test extensively.

No, I haven't build CMYKOG profiles. You'll need a RIP to use that right? One cannot print or softproof in Photoshop with a 6 channel profile? I am on a Canon iPF8100 printer, so I don't think I can use a CMYKOG profile. For RGB printer profiles, Scott mentioned before that starting with a large enough patch set, one will not see any visible benefit from running the optimization step. I've been too preoccupied to test that.

By the way, have Scott or you noticed that when the patch sizes get really huge, like 5837, saving a mxf measurement file causes i1Profiler to crash? I have issues when I scan M0, M1 and M2 at the same time. It can handle M0 just fine, less total data. Like there is a memory limit on the mxf format. Smaller files have no issues at all.

[samueljohnchia]

I think it's important to separate color management from color correction, and therefore I try to find the settings that produce what I consider to be the best conversion that visually preserves the original image without "correcting" or "enhancing" it. With this in mind, I feel that the contrast setting is more of a subjective "enhancement" control as opposed to a valuable color space conversion adjustment. Make sense?

Scott, that is exactly my sentiment. If one wants more contrast for a particular image, the printing profile should not be the 'correction' method. Otherwise softer images that you want to print soft will also get hit with the contrast increase. I want the most 'neutral' setting for the tone curve, and with the best amount of separation, a long smooth tone in the grayscale, as visually linear as possible. I remember discussing with Joseph Holmes about the L* curve not being visually linear enough. Can't remember how he quantified it. I'll add contrast in post-processing if I need to. I tend to dislike "overly processed" imagery.

The saturation slider is fantastic - it's one of the crown jewel technologies acquired from Monaco. The way it works is brilliant. Increasing saturation here doesn't effect or over-saturate what I like to call "mid-gamut" colors like skin tones. Instead, it controls the "edge gamut" colors. Think about super red saturated fall leaves and all the delicate veins and texture within the leaf. Use a low setting and the edge gamut colors are less saturated but full detail is present. Use a high setting and the edge gamut colors are much more saturated at the sacrifice of tonal detail. I think there's a sweet spot that gives the best of both worlds. But I won't spoil the movie - why don't you do your own testing and let's compare notes. :-] Same with Neutralize Gray.

I'm on it. I realise that I left the neutralize gray at 0, which is not the default setting. I now wonder what that has done to my test results. Maybe I will not notice the 1 value changes in only one R, G or B channel anymore, I don't know. But then, 0 is no neutralizing, so I might see a greater effect if I left it at 50.

I worked late into last night creating my own custom targets to test the edge gamut of saturated colors. My initial reactions to the saturation are similar to yours. I will describe them in detail in a later post, and any other unusual findings.

Exciting to see you do this. Exhaustive testing like this is what separates the pros from the rest.

Scott, I'm not working at the moment so I can dedicate my time to doing this. I'd rather be doing something else. I was just at an art show, and there was this french photographer who made his own inkjet printing paper from Egyptian cotton, another who printed with the Piezography inkset, and still others on standard setups. They were selling their artwork at enormous prices. These are the "pros" too. But hey, they collect their money at the end of the day and go relax on their yacht or something. The print quality was absolutely rubbish. Worse still, I saw a lot of digital processing flaws, so even with a wonderful inkset like the piezography, I am sure I can do better with both eyes closed on my iPF8100+OEM inks. My eyes hurt so bad after the show. Honestly, I think nobody really cares that much to figure it out to the end. Perfection is just so elusive. It is so easy to give up and do something else. Seriously, there are times where I doubt I can see the differences if I didn't do a side-by-side comparison. Who is ever going to spot it at an artshow?? I'm not trying to show off here, but I think I am pretty good at visually judging prints objectively without comparisons, but this is just so subtle! I am reminded of a story I heard from an audiophile - "Can you hear the man cough at 2:05, fifth row, center column, third chair from the left?"

[Scott Martin]

No, I haven't build CMYKOG profiles. You'll need a RIP to use that right? One cannot print or softproof in Photoshop with a 6 channel profile? I am on a Canon iPF8100 printer, so I don't think I can use a CMYKOG profile.

Yes, you need a RIP and yes Photoshop doesn't have much support for 6 channel profiles. You could use 6 channel profiles with your printer with the right RIP. The colorspace used is all about the RIP/driver - not the printer.

For RGB printer profiles, Scott mentioned before that starting with a large enough patch set, one will not see any visible benefit from running the optimization step. I've been too preoccupied to test that.

That's a big deal worthwhile test, IMO. There's a convenience/quality sweet spot for sure. And it comes way before 5000 patches. At some point having too many patches actually increases the chance that something will go wrong and bad measurements could be introduced...

By the way, have Scott or you noticed that when the patch sizes get really huge, like 5837, saving a mxf measurement file causes i1Profiler to crash?

Haven't seen that in a long time as that many patches is just insane with this engine. More patches doesn't equal better results like it used to.

[samueljohnchia]

Yes, you need a RIP and yes Photoshop doesn't have much support for 6 channel profiles. You could use 6 channel profiles with your printer with the right RIP. The colorspace used is all about the RIP/driver - not the printer.

Scott, will there be improved quality over what I can achieve with the 16 bit plug in from Canon? I read that Tyler has spent some time inventing a custom dither that is superior to the standard Epson driver. I find the dot formation by both Canon and Epson OEM drivers rather coarse. I can see the printed dots with my naked eye under reasonably bright light. I would be excited to know if I can tweak it away. 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.

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?

Would running the calibration on the paper that I print on most often make the printer more linear for that combination? It would invalidate all my other current profiles though.

That's a big deal worthwhile test, IMO. There's a convenience/quality sweet spot for sure. And it comes way before 5000 patches. At some point having too many patches actually increases the chance that something will go wrong and bad measurements could be introduced...

I am also wondering if introducing a large number of grays and near grays actually improve the separation and neutrality in the grayscale. That would take me down the road of customizing targets. I haven't found any literature that describes in a scientific fashion an optimal way to select targets for printing photographic images. I am thinking that one could use around 2000 patches for color and near neutrals, and 1024 grays, 4 for each 8 bit integer, so the average would be more representative.

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

Haven't seen that in a long time as that many patches is just insane with this engine. More patches doesn't equal better results like it used to.

My initial testing some months ago show me that a 5837 profile has a visibly larger gamut, more neutral grayscale, higher dmax and "more accurate description of certain colors" (if my printer+paper combination cannot produce a perfectly smooth gradient for that color, the profile reflects that) than 2033 patch you recommended elsewhere on the forum. The downside is sacrificing some smoothness in the profile, which appear to be correctable by the smoothness slider. But I haven't tested this extensively with different printer+paper+driver combinations to know for sure.