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Author Topic: Profiles generated from coated versus uncoated canvas, unscientific.  (Read 1578 times)
bill t.
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« on: December 17, 2012, 08:14:21 PM »
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For the unscientific heck of it, here are some graphs that compare the profiles generated from uncoated and coated samples from the same patch print.

The canvas is Epson Exhibition Canvas Gloss, which has recently undergone several changes in appearance and mechanical properties.  Have been running profiles to keep track of it all.  These graphs are from the very same same patch print made on a very recent batch.

The graphs show the gamut volume of coated canvas (in wireframe) over the uncoated canvas (as the colored hull).

Coated gamut volume in 791K units, versus 756K units uncoated.  Coating lost some dmax on certain certain dark colors, but gained in most bright and midtone colors.  Coating gained some gamut in the green and blues, at the expense of the already strong yellows, which is a reasonable tradeoff for landscape. BTW this and other gloss canvases are MUCH stronger in the cool colors than any matte canvas I have ever used.

So there you are!  Think I'm gonna use coated canvas profiles from now on.  In the past I had very strange results from commercially made profiles of coated canvas, don't know why that is.

Prints from the my coated profile are much prettier, especially in the more articulated brighter areas which makes those prints look distinctly more lively than those made with the uncoated profile.

Worth noting that I was able to scan the entire coated patch set without having to re-scan a single row!  Old version i1Pro.  With the very same uncoated patch set I had to scan almost every row at least twice, and sometimes 4 or more times.  Think I'll make a really big patch set tonight.
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Dan Berg
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« Reply #1 on: December 19, 2012, 03:08:15 AM »
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Very interesting,thanks for your efforts.
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del@pscc.com
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« Reply #2 on: December 19, 2012, 11:43:45 PM »
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Bill --

Very timely!

What printer/ink set are you using?

I'm getting ready to do something similar with Epson Exhibition Canvas Matte on a 9900 with MK ink.  I thought I'd read sample charts as follows:
 - when first printed
 - after 1, 2, and 4 days
 - 1/2/4 days after varnishing (I'm currently using Glamour II 50/50 matte/gloss -- 2 coats)
 - after another 1/2/4 months

I've seen already that I need to run new profiles for each production batch (I try to buy several rolls at once to maintain consistency) and it's also helpful to average readings from 2-3 charts.

I'll report back as things progress and will be eager to follow your efforts.

Any suggestions are most welcome.

Dave.

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digitaldog
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« Reply #3 on: December 20, 2012, 11:25:56 AM »
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Viewing the two gamut maps, depending on the viewer may indeed be not too scientific. See:

http://www.colorwiki.com/wiki/Color_Management_Myths_26-28#Myth_26

Doesn't look like we're seeing ColorThink gamut maps.

Better would be to forget gamut maps, just produce a dE report of the measured data from both papers in ColorThink. You'd see where in color space the greatest differences really are.
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Andrew Rodney
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bill t.
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« Reply #4 on: December 20, 2012, 12:11:28 PM »
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Canon 8300 with the standard Canon inks.

Was fun to do, but bottom line is that variations in scanning technique and other things probably add up to noise errors that are as big as minor variations in the media and ink set.  I called my efforts "unscientific" because for instance I didn't do basic stuff like comparing back to back measurements done at the same time, and as you say averaging, and on and on.  Real science is too much work!

So to be honest my only truly reliable conclusion from that lazy experiment is that for my equipment, it's easier to scan coated canvas!  

And to a lesser extent, the 3d graph of the coated hull as presented by i1Profiler showed a more even wireframe patchwork for the coated hull, which I take as evidence of relatively clean data.  And it's not too hard to see that prints from the coated profile is a little more peppy in the highlights...although I have seen cases where the wrong profile applied to a particular media is sometimes jazzier than the correct profile.

But OTOH, with a set or readings extended over time you might usefully be able to pick up long term systemic errors...if only in the puck!  All of which reminds of my favorite long-term science experiment failure which was the "discovery" of a planet around Barnard's star, which after countless, painful, hunched over hours of precision measuring turned out to be a periodic error in the gear train of the telescope.  And more recently the the faster-than-light Cern neutrinos that were tracked down to a badly inserted plug.

Thanks for that myth-busting link digitaldog!  I definitely need to spend some time there.  Appeals to my deep cynical streak.  We so badly want to have Faith in the things we depend upon, and that faith is so often misplaced.

Those are graphs from iccview.de.  Absolutely for free and at the very least are useful for ballparking the differences between fairly different media.

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JeffKohn
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« Reply #5 on: December 20, 2012, 12:20:50 PM »
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Even though it's somewhat counter-intuitive, I get my best results on coated glossy canvas (Innova in my case) using a profile created with uncoated test charts. The main difference seems to be the profile black point, and even though you could argue a coated profile would be more accurate, for whatever reason the profile with the lower black point works better and produces better final results for me.

But as Bill mentioned, there's a certain amount of variability in the profiling process, so repeating the experiment with a new set of profiles might possibly yield different results. It could just be luck that my uncoated profile turned out so well, but since I have a good profile I'm sticking with it.
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digitaldog
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« Reply #6 on: December 20, 2012, 12:25:16 PM »
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Those are graphs from iccview.de.  Absolutely for free and at the very least are useful for ballparking the differences between fairly different media.

Only if it's using an Absolute Colorimetric intent to plot them using the correct tables like ColorThink.
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Andrew Rodney
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bill t.
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« Reply #7 on: December 20, 2012, 01:23:27 PM »
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OK, so what's the case for a landscape photographer / inkjet-jocky like me having a copy of Colorthink?

Wow, just looked at this video on this Colorthink page.  I had no idea!  Sounds to me like color management professionals have their work cut out for them!

https://www2.chromix.com/colorgear/shop/productdetail.cxsa?toolid=1208
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digitaldog
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« Reply #8 on: December 20, 2012, 01:25:29 PM »
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OK, so what's the case for a landscape photographer / inkjet-jocky like me having a copy of Colorthink?

Probably none unless you want to go down the CMS rabbit hole in grand detail. It is the color geek swiss army knife but I'm not sure how useful it is to others.
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Andrew Rodney
Author “Color Management for Photographers”
http://digitaldog.net/
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