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Author Topic: DIY Scanner IT8 using I1Profiler's Scanner Profile  (Read 521 times)

Doug Gray

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DIY Scanner IT8 using I1Profiler's Scanner Profile
« on: November 11, 2019, 05:37:53 pm »

Currently working on making printable IT8 charts for profiling scanners.
Designed for printing on Canon Pro 1000 series glossy media.

Features:

Printable charts are in ProPhoto RGB (print using Abs. Col.) and accompanying LAB text file that can be dropped into I1Profiler's list of scanner reference docs.

If you profile your printer with an I1Pro 2 or i1iSis this provides better results for scanning printed images than IT8 charts made with wet processes and not individually measured. I'm getting average dE's with this of about 1.0 on my V850 which is well under the dE 2-3 I get with the X-Rite chart that came with the scanner.

But wait, there's more!

The charts are provided in two images which can be scanned by either an I1Pro 2 or an i1iSis. Included is a utility to convert the I1Profiler CGATs measurement file into a LAB text file that I1Profiler uses. When used this way you can create a precision LAB text file that corresponds exactly with what your printer makes. You get a near perfect IT8 that corresponds to the printer and spectro you use for your printer profiles.

I have been working on and testing this for the last week and really like how it's turning out. Not quite as good as going through Argyll (.4 dE v .6 dE ave error) but that requires a bunch of specialized Matlab code and a steeper learning curve.

It will be going up on github. Stay tuned.

Update:
I've been using the Lab values from a Monaco (X-Rite) chart to make printable IT8 charts. While they work great with average scanned dEs that are quite low, there are outliers with as much as dE4. To some degree this is due to the limited (288) patches in their IT8 chart. But a larger factor is that the more saturated, brighter, colors that ink jets make are way outside the gamut of the IT8 charts which are made with photo paper circa 1990.

So I bought a copy of the IT8 ANSI spec and am using my Pro1000 on glossy as the target media. One nice result is that patches from the much larger printer gamut will be included but it will still conform to the IT8 spec. I'm hoping it reduces the outliers but won't know until I test it. Ideally, one could spec. a much larger chart patch count and have I1Profiler work with it but I don't see a way to do so. What I've done up to now is use Argyll with a couple thousand patches. This works really well but I use Matlab tools people don't generally have. Getting something simple that people can use to make better scanner profiles using I1Profiler would be more widely useful. So I'm hoping this more inkjet friendly IT8 (that can be scanned with I1Pro2 or iSis to create reference files) will provide this.
« Last Edit: November 17, 2019, 06:23:58 pm by Doug Gray »
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