[argyllcms] Re: CMP Digital Target 3 (not 003)

  • From: Nikolay Pokhilchenko <nikolay_po@xxxxxxx>
  • To: argyllcms@xxxxxxxxxxxxx
  • Date: Sun, 08 Mar 2009 01:29:14 +0300

Pascal de Bruijn wrote:

> I'd like to hear your opinion on the target designs, and what is expected
> to have the best results with Argyll.
> I'm aware it's hard to comment on production quality... But assuming
> production is up to snuff... Which target is "best" designed? Or shouldn't
> I expect any better results than with my IT8 target?

I think, the more patches on target will give the more accurate results. But 
when the angle size of a patch is rather small for your camera, the lens flare 
can increase measurement error. I intuitively prefer the chaotic patch 
distribution on target, but it worth to be mentioned, that depending on lens 
quality and shotting conditions, the patches can influence each other.

> Does anybody here have ColorCheckerDC reference files? I can't
> find them on X-Rite's website.
> Are ColorCheckerDC targets individually measured? or batched?
> or are they manufactured to a very small standard deviation?

I have ColorChecker SG. You can't find reference on X-Rite site, because the 
Color Checker is intended to use with X-Rite software only, I suppose. I found 
one file in X-Rite folders on my computer. But I don't use them. I built my own.
I've attached spectrum measurements of my Digital ColorChecker SG in 
DigitalColorChecker_Nikolay_Po.zip. The measurements was 3-time sampled and 
averaged. I've included corrected Graeme *.cht (with slightly more wider 
borders between patches because the shadow from plastic frame presence) and 
D50.cie and D65.cie - XYZ/LAB refrence for my particular target copy in 
addition. I think, there is very small standard deviation in production, 
because I've get no any reference file in shipment.
If You want to compare different targets, I recommend you to see the spectra 
I think, the 140 patches on DCCSG is rater small, so, I can't recommend you to 
buy smaller DC ColorChecker. IMHO.

By my experience, with ColorChecker SG only the matrix profiles can be build 
for my camera with 140 patches of ColorChecker SG. The LUT profiles haves 
deviations (see below) and in generally don't applicable even for simple 
daylight illumination. Furthermore, only the matrix+gamma profiles can adequate 
(but not exact) predict the out-of-target-gamut colors, while the matrix+shaper 
profiles are often incorrect, the LUT profiles has huge unpredictable errors. I 
wasn't able to take even one successful image with LUT-profile, but 
successfully taken images with matrix profiles with Argyll CMS (I haven't use 
other software). It seems that single gamma profiles generally better than 
different channel gamma.

I've bought my first target from Ukraine for $32 in 2006. They have 288 patches 
printed on multiink inkjet printer with high gamut.

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