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Author Topic: i1Profiler test chart generation  (Read 1764 times)
rasworth
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« on: April 15, 2012, 03:22:41 PM »
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Supposedly the i1Profiler built-in chart generator is the way to go, so I cranked out a couple for one and two 8.5x11 sheets, 405 and 810 patches respectively.  My intent was to fill the letter size page with as many patches as possible readable by an i1Pro, which is easy enough to do using the built-in tool.

The single page 405 patch target contained 9 "neutral" patches, i.e. 0-0-0 to 255-255-255, equally spaced.  The two page 810 patch target contained 23 neutral patches.  I then went for the maximum number of patches to fill up a 13x19 sheet, turns out for efficiency one has to create two 9.5x13 targets and rotate and stitch together to more or less fill up the area.  I was somewhat surprised to find this resulted in only 12 neutral patches.

I realize driving the printer with equal RGB value patches may or may not actually create neutral patches on a given paper, but I was still surprised at the wide range, or more specifically going to more patches can greatly reduce the neutral inputs.  Anybody have an idea as to the basic workings of the target generation algorithm?

Richard Southworth
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bill t.
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« Reply #1 on: April 15, 2012, 04:27:55 PM »
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Perhaps with larger numbers of samples it's easier to infer where "neutral" is, smoother curves or something.  With smaller numbers of samples perhaps interpolation is less accurate and it's necessary to be more literal about tying down the neutral points.  How's that for a WAG?
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JeffKohn
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« Reply #2 on: April 15, 2012, 04:43:24 PM »
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Yeah and I would be more interested in how many "almost neutral" patches are included as patch count goes up. Having a lot of true neutrals like 50,50,50 in the test chart might not be as useful as having lots of patches like 50,51,50, or 50,51,49, etc.
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Alan Goldhammer
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« Reply #3 on: April 15, 2012, 04:49:27 PM »
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Yeah and I would be more interested in how many "almost neutral" patches are included as patch count goes up. Having a lot of true neutrals like 50,50,50 in the test chart might not be as useful as having lots of patches like 50,51,50, or 50,51,49, etc.
My reading of the OP is that these are not all identical 50, 50, 50 but a B/W stepwedge and that has more steps with higher patch count.  You can do this within ArgyllCMS by specifying how many steps you want and I go for 51 which helps with smoothing.
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digitaldog
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« Reply #4 on: April 15, 2012, 04:54:55 PM »
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Anybody have an idea as to the basic workings of the target generation algorithm?

Yup, the guys who wrote it. <G>

You can generate custom target with your own RGB values using ColorPort but unless you have specific reasons to do so (like you have company colors you want to track), just let the generator do it’s job. You want a lot of grays? Use the optimization process after initial profile creation:

http://www.i1upgrades.com/2011/08/how-to-use-the-tc-2502-gray-optimization-chart/
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Andrew Rodney
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rasworth
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« Reply #5 on: April 16, 2012, 01:24:41 PM »
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Ok, cranked out an optimization on a profile I did 7 months ago for Red River Ultra Pro Satin on an Epson 3880, a semi-gloss paper with mild OBAs.  Not wanting to scan 7 pages with an i1Pro uvcut I auto generated a 405 one page optimization target, printed, scanned, and then created an optimized profile.

I noticed the 405 patch target was about 60% relatively unsaturated patches in regular patterns, seemingly intended to stay close to the neutral axis.  The remaining patches were generally very saturated, a crazy quilt all over the map.

I had generated the original profile with 1000 i1Profiler auto generated patches, maxing out the number that would fit on a 13x19 sheet with one image.  I printed test images for the old and new profiles and compared, nothing different I could see.  I examined both profiles in ColorThink, very slight difference in the neutral curves but not enough to make a visible difference.  My conclusion is for a well behaved printer (sample of one) the original profile is sufficient, no value added with optimization.

Richard Southworth
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digitaldog
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« Reply #6 on: April 16, 2012, 01:31:21 PM »
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Not wanting to scan 7 pages with an i1Pro uvcut I auto generated a 405 one page optimization target, printed, scanned, and then created an optimized profile.

A 405 patch optimization of what? If you are having i1P just build a colored target, then your conclusions are similar to mine. And using an iSis, I did testing where the secondary optimization target had thousands of patches. More than the original. Running the profile through color patches, and then placing that into ColorThink Pro to generate a color list, the max dE’s were below 1. So in that case yes, thousands of colored patches generated for optimization was useless. Now try the 2500 patch gray target of Marc’s. I suspect you’ll see a difference as I did on my 3880. Here you are targeting just neutrals and off neutrals and a boat load of them. IOW, a 2500 patch target like Marc’s and a 2500 (heck, 5000 patch) optimization from i1Profile using other colors is a big difference in terms of the end results.
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Andrew Rodney
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rasworth
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« Reply #7 on: April 16, 2012, 03:00:04 PM »
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I wasn't trying to suggest that a targeted optimization, i.e. for neutrals, wouldn't provide a benefit.  However, without other than an i1Pro I'm not willing to take on the 2500 patch target.  I read the link you provided, the poster stated he would work on a smaller target but so far not available.  The real question to me is how many patches are required to achieve meaningful results on improving neutrals, can we get the number down to something that will fit on one letter size, or 13x19, or something more manageable for us common folk.

Richard Southworth

Added by edit - Actually it's not as bad as I implied, would take two 13x19 sheets to print out, total of 93 lines to scan with an i1Pro.  Not a pleasant task but not that bad for one or two profiles.  Maybe someday.

Added by second edit - Oops, brain cramp, would require 3 13x19 sheets.
« Last Edit: April 16, 2012, 07:02:48 PM by rasworth » Logged
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