[argyllcms] Re: Limitations on Colormunki patch sizes?
- From: Serhat Abaci <serhat@xxxxxxxxxxxxxxxx>
- To: argyllcms@xxxxxxxxxxxxx
- Date: Tue, 10 Dec 2013 21:01:46 +0100
I would love to see a professionally produced maybee crowd funded
Colormunki scanning ruler / scanning helper for our argyllcms tiny patches
2013/12/10 BC Rider <bcrider99@xxxxxxxxxxx>
> I've been playing with patch sizes for the Munki and I thought some
> people might be interested in the results.
>
> TEST SETUP:
> I tested mostly on plain paper. I generated a 156 patch target using
> default targen values. I then edited the ti1 file to create sections of
> identical colors (10 patches long). I did this four times in the file. I
> then printed the target using the NON-random layout. I tested a range of
> sizes from 6mm up to 13.7mm (CM -h setting). I did multiple targets with
> multiple scans and compared results using the verify tool and direct
> inspection in Excel.
>
> RESULTS:
> 1) I found Argyll poor at detecting row contamination (i.e. width). I
> saw degradation in Excel long before Argyll flagged errors. Staggered
> layout (i.e. CM layout) improved detection performance over non-staggered
> layout (i.e. i1pro layout) but still not good.
>
> 8.2mm and 13.7mm are "magic" numbers that allow the target rows to be
> perfect gridlines for the ruler. The ability to simply lay the ruler down
> on the gridline without guesswork AND the fact the Munki is self-centering
> under these conditions is very significant. All other widths require
> some estimation increasing the risk of misalignment (unless one uses an
> extra alignment spacer with the ruler - e.g. 10mm patches would require a
> temporary 5.5mm spacer inserted which is removed when scanning).
>
> 2) Patch length issues are better detected in Argyll. However I noticed
> minor degradation in quality as one approached the maximum scanning
> speed. I also noticed some quality issues at extremely slow scanning
> speeds (i.e. 20 seconds or more per line). This happened regardless of
> patch size. Best results seemed to be scanning between half and
> two-thirds the maximum scanning speed. Overall I found anything from about
> 8mm and longer worked fine. There is no practical difference in quality
> and the scanning speeds are all reasonable.
>
> 3) Some (very few) patch sequences had issues with patch detection using
> smaller spacers so I settled on 1mm spacers in all scenarios. I also
> noticed randomized targets were much more tolerant of small spacers. In
> fact spacers may not even be needed on randomized targets but I didn't
> investigate this further.
>
> 4) Sometimes there were one or two data points with dE errors
> disconnected from the group. Very occasionally a truly wild data point
> occurs. This happens regardless of patch size. Rescanning the patch brings
> these back in line.
>
>
>
> CONCLUSIONS:
>
>
>
> Because Argyll is insensitive to row contamination, I would use a
> ruler for the CM -h setting and smaller patch sizes. For truly "mindless"
> scanning constraining BOTH sides of the Munki is highly recommended. I've
> attached a small photo showing the idea. An aluminum meter-stick cut in
> half and glued to spacers (use the Munki to set the spacing) is simple
> and effective.
>
>
>
> Given the proper scanning guide, 8.2mm seems a good general choice for
> patch width. In my tests, I didn't see any benefits when using larger
> widths. I also found the double-sided guide generated very robust
> alignment and tracking.
>
>
>
> Without checking the measured data one can unknowingly build profiles with
> bad data. This seems to be true regardless of patch size. So I scan each
> target twice and compare results using the Verify tool and, if necessary,
> rescan offending lines. I then average the two files prior to making the
> profile (using Average tool).
>
>
>
> BOTTOMLINE: Everyone's needs are different so there probably isn't
> a perfect target. For general use, I chose the CM target layout because
> it has staggered patches and when scaled down to 8.2mm width the 8.4mm
> length works fine for me. The downside of the CM layout is a tremendous
> amount of wasted white space at the beginning and end of each row. I have
> to mess about in my image editor to remove the extra space.
>
> The i1pro layout is not bad if scaled to 8.2mm width. Some may prefer
> the longer length. I can see why people use it. But I find the patch
> length longer than necessary and prefer a staggered layout. On the
> upside, the i1pro layout doesn't waste nearly as much space at the start
> and end of each row so is a better choice for those wanting to avoid the
> image editor hassle.
>
> Overall the Munki seems more capable and versatile than most devices.
> I've scanned from about 50 patches to 800 patches on a single Letter sized
> sheet. IMO, all scenarios are perfectly valid under the given
> circumstances. This versatility is a unique strength of the Munki so it
> would be nice to see the Munki better supported in Argyll. To that
> end, I'd suggest Printtarg updates to:
>
> 1) Allow scaling patch width and length separately,
> 2) Allow setting the white space at the beginning/end of each row
> (perhaps specify minimum mm required?)
> 3) Option to not print strip indexing and/or allow font size scaling
>
> Advanced users could then tailor either the i1pro or Munki layouts to suit
> virtually any need.
>
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