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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