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Author Topic: Some questions about working with Absolute Colorimetric intents  (Read 3915 times)

BobDavid

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All of the dog photos were commissions. I loved taking pictures of ordinary dogs for ordinary people. I loved not having to deal with ad agencies, art directors, account executives, etc. ...Being that you are curious about monetary remuneration, a session and a single photo printed onto  17" X 22" commanded $1,200. ... Due to severe autoimmune health problems, I could no longer photograph dogs. Although I usually took around 30 photos per session, the amount of time lying prone along with moving a light on wheels with one hand while framing the picture in the camera with the other became too much of a strain. Throughout the time I photographed dogs, I did a couple shoots for national campaigns. Although the pay was good, the stress of dealing with ADs, account execs, and superfluous people shuffling around in my studio was not conducive for taking pictures of dogs.

I've also taken studio photographs of birds, hedgehogs, and tarantulas. I only photographed snakes once and that was for Hill Holiday in Boston. Once was enough. I don't like bats, snakes, and rats.
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digitaldog

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I looked over all the images. The dog work is the best by far IMHO; quite stunning. Horizons; some very interesting and lovely. I will refrain from commenting on the other's.
I am probably equally guilty as many of the photographers who's work I view: too many photographs. Less is more. I suppose that's why in the old days, I'd get a rep's who among other tasks, aided in being an good photo editor for promotion of my work.
It's too bad we got off on the wrong foot about photography, I know why The technical stuff about your problems posting about color, outlined and with suggested outside peer reviewed articles, stands.  ;)
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Andrew Rodney
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Doug Gray

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Well - no they don't. They can't magically make all those multi-millions of sRGB and AdobeRGB profiles out there conform to a new definition of how to make display profiles, nor can they magically changed how existing CMMs and applications work, nor can they dictate how CMM's implement their APIs.

So for instance, using ArgyllCMS Absolute still means Absolute.

lol. That's why I made the allusion to Humpty Dumpty in Lewis Carroll's exchange.

The ICC has addressed their unique interpretation of "Absolute" this way:
The "absolute colorimetric" rendering intent is renamed "ICC absolute colorimetric", to avoid confusion with CIE absolute colorimetry.

Appears that Adobe's CME adopted the revisionist definition even on long existing profiles. I would actually prefer to use Microsoft's but it turns out to have significant errors converting sRGB in the standard intents.
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BobDavid

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Now that's more like it! VERY nice. You can shoot, no question. Now if we can simply get you to enter a technical topic and post technically correct comments, we're on the same page.
BTW, it is far, far more difficult to produce the very lovely images of dogs on your site, then learn and post technically correct text about color and imaging. So I have hope you can eventually do both.

Thank you for the compliment. ... I have technical chops. Admittedly, I'm not a color scientist, so my argot is sometimes off the mark. But I can assure you, I know how to read a historgram, edit photos non-destructively, and produce exhibition quality  prints. I understand and use color managed workflow--I don't waste material. I am in tune with what I see on the screen and what the printer spits out. ... I have the tools and knowledge for generating ICC profiles, although in this day and age, I settle for canned profiles. I cannot create a better ICC profile for Epson papers for an Epson P800. When my studio was in full swing, I often made custom profiles, and on occasion hired "experts in the field" to create them. I am sure you have the skill to create better ICC profiles than the canned ones. ... After working with cine film, color timing, reading control strips, etc., I burned out on minutia. I self-learned digital photography. ... I enjoy straight ahead jazz. Some of the best musicians were not able to read charts. Perhaps they had dyslexia, lacked interest, or stubbornly refused. ... Apparently, a guy such as myself lacks the qualifications to participate on this forum. I'll save for the color scientists and the newbies who request help with technical issues. ... I would like to be on good terms with you. So, moving forward, I will practice restraint and not ruffle feathers on the Colour Management forum.

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« Last Edit: May 11, 2018, 12:56:10 PM by BobDavid »
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Doug Gray

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Now that's more like it! VERY nice. You can shoot, no question. Now if we can simply get you to enter a technical topic and post technically correct comments, we're on the same page.
BTW, it is far, far more difficult to produce the very lovely images of dogs on your site, then learn and post technically correct text about color and imaging. So I have hope you can eventually do both.

This is very true. You are both far more skilled photographers than I am. I come to it from the engineering side and a stint in a company that made various imager products with a focus on quality control issues, mechanical registration, color "accuracy" and such. My knowledge of printing tech., which was necessary for making certain custom targets with accurate colorimetry required deep diving into the physics as well as the more geeky aspects of ICC profiles.
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Doug Gray

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Apparently, a guy such as myself lacks the qualifications to participate on this forum. I'll save for the color scientists and the newbies who request help with technical issues.[/url]

Not at all. First, you have good control over color management and understand soft proofing. While your use of Abs. Col. is unorthodox, you have combined it with good soft proofing practices and Photoshop adjustments to produce what you want and have avoided the gotchas associated with high key clipping because you soft proof effectively. Ultimately, color management is about enabling photographers to produce appealing art.

But to summarize why AbsCol compared to RelCol is rarely used in printing photos it's these two factors:

1. Clipping when L* exceeds the paper white.

2. Neutral colors are printed neutral and not shifted to the paper's actual white point. This creates pretty awful effects on prints with a white point that is more than 1 or 2 dE tint (a* and b* only). But it's only awful when the print has a white border. Borderless prints are printed more consistently with AbsCol as the printer takes out any tint the paper has. However, a significant tint reduces the printable gamut further beyond the effect in #1.

Soft proofing and adjusting as required is a way of dealing with the above without going into the tech. weeds since WYSIWYG. Still, while soft proofing isn't perfect for sundry reasons it is a huge leap above not soft proofing.
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BobDavid

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This is very true. You are both far more skilled photographers than I am. I come to it from the engineering side and a stint in a company that made various imager products with a focus on quality control issues, mechanical registration, color "accuracy" and such. My knowledge of printing tech., which was necessary for making certain custom targets with accurate colorimetry required deep diving into the physics as well as the more geeky aspects of ICC profiles.

Thanks, Doug. I'm not an engineer, nor am I a scientist. It's people like you who've made it possible to work in the digital domain. I also take my hat off to those who've advanced analog stills and motion photography--the same for lens designers, those who design image sensors, etc.. Funny thing, I did my graduate work at MIT, was awarded a two-year research fellowship, and was the first recipient of the Kepes Prize. I have a keen interest in visual perception, and dipped my toes in neural science. I became friendly with students, physicists, electrical engineers, computer scientists, etc.  I was fortunate to be present during the time the Media Lab was set up.

My special interests centered on depth perception (I'm stereo blind as well as have difficulties with recognizing faces), afterimages, and designing experiments to test human color perception.

I'm currently a member of a makers space. Many of the folks there are scientists and engineers. Lately, I've been tinkering with OLED displays and building a robot that will read bitmap files and use RGB LEDs to draw for time exposures. I do not have a background in EE. Fortunately, I've got access to those who do. Having been a lifelong tinkerer has afforded me opportunities to acquire skills without necessarily understanding the underlying technology.
« Last Edit: May 11, 2018, 02:53:16 PM by BobDavid »
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BrianToth

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So, the project I've been struggling with the last 4 months has been to "simply" reproduce a bunch of old photos (40s-90s) as accurately as possible, e.g scan them, print them, and hold them up side-by-side and have them look pretty close. This has been a project that's been on my mom's to-do list for a while but I had been putting it off because my past experience with a non-color-managed workflow of scanning and printing had been extremely frustrating and disappointing. It's been suddenly made a priority because of family circumstances I don't need to get into, but the hope was to have some of this working quite a while ago.

Last year I tried doing some research so that I could "do it right" - so I bought an Epson v800, i1Studio, a Canon Pro-10 and a Pro-100 (pigment vs dye), subscribed to Adobe, bought VueScan, got sample paper packs from different sources, a Rotatrim, and even sourced an old English Deckle cutter that nearly perfectly matches the jagged cuts of the old B&W photos – it's surprisingly awesome btw. Anyway, I tried to jump right in and just push the buttons and make it work and everything looked like crap. I spent months researching everything I could understand, with a lot of misinformation and red herrings. I was very disappointed with the X-Rite results, but I think some of that was my ignorance, broken printer profiles, and a lack of documentation. I spent months reading, experimenting, re-reading, playing with Argyll CMS (which really brings a lot of capability to my i1Studio!), etc. without much luck, landing me here.

I have a computer science degree, I write software, repair computers, and consult on other IT-related areas so I'm comfortable with the command line, working with numbers, writing scripts to get things done, etc. But this color management stuff is new to me obviously, and I'm not an artist and have trouble speaking in color. I would like to think that there's an ideal workflow for my reproduction project, but there's a surprising lack of documentation for scanner-based reproduction work.

Like I mentioned back on page 1, most of the stuff I came across specifically said to never use Absolute, but in reading some other threads on this forum I gave it a shot and it helped quite a bit with what I was trying to do. Now, it's possible it's still wrong and it's just compensating for some other broken part of my workflow which I'm willing to accept.

One of the threads I gathered info on using Absolute was this: Getting Blue Colors "right" - http://forum.luminous-landscape.com/index.php?topic=106697.0  There were a few choice quotes from that thread:

Quote from: Doug Gray
If a friend gives you a 4x5 borderless print and asks you to enlarge it to an 8x10 the proper way to do it is to scan it with a scene referred profile. Resize it. Then print it using Absolute Colorimetric Intent. As long as the print media has a gamut that is as large as that in the scanned image there is no art to it. Just the science and the numbers. The OP is scanning something and wishes to reproduce it. A good scanner profile and AC printing is the best way to do it.

Graeme Gill had a post in that thread also about tracking the color through the workflow, which I'd like to do though I had trouble interpreting how to perform the exact steps. I might circle around to this again when I get back to scanning.

Doug also had good advice at the end of that thread:

Quote
Divide up the issues and address one at a time. Trying to get everything "right" without using instruments to measure each aspect separately, is a hard and frustrating process.

Which is what I'm attempting to do currently is break things up into manageable chunks.  Thanks to the help I've received here I have improved my computer to printer results, at least numerically. Though I still have a follow-up about printing in absolute:

1. Given a hypothetically perfect paper profile: if printing an image using Absolute to two different papers that have a large enough gamut for the image, would the output look identical? I ask because even now that my paper profiles have dEs of around 1.0, there's still a visible difference in color temp between my test prints on different papers. They're very close, but I can tell that one looks warmer and the other colder.

Image white patch: 95.190, -1.030, 2.930

Plus Glossy II absolute: 94.190, -1.968, 3.164
Plus Glossy II white point: 94.5493467, -0.813282, -2.3624075

Pecos Gloss absolute: 94.770, -1.265, 3.539
Pecos Gloss white point: 94.959037, -0.0461172, -1.3828287

The Glossy II print looks a tad yellower to my eyes. The Glossy II is glossier if that matter.

2. To see what the affect would be with Relative (because it seems like it's the thing to use for most other circumstances), the same white patch for the Pecos Gloss shifts to 90.39, -1.093, 1.484.  Despite the dramatic drop in lightness, the actual print seems to have more contrast. Maybe I don't need to get distracted by that just yet, but it wasn't what I was expecting.

At any rate, where I'm at now seem so look like the right direction for printing. Based on data I've collected today I think it's still primarily my scanning that's off by quite a bit. Not sure if I should continue on this thread with that topic or start a new one. I suppose it would still technically involve absolute intents.
« Last Edit: May 12, 2018, 01:56:06 PM by BrianToth »
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nirpat89

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Hi, Brian:

Kudos to you for making so much effort to reproduce the family photo album...hope your siblings and relatives appreciate the pains involved (not to mention the time and the money) to get them just right.  My patience would have run out on day 3.  I have postponed my own project to do something similar indefinitely for the fear of amount of work involved.   

A couple of general points and a (wild) idea:

Given that the original photographs would have been printed on a wide variety of papers each with its own texture, reflectivity characteristics, and base color, spanning decades in time and technology - would it not be practically impossible to reproduce them all on a couple of inkjet papers using a generalized workflow? 

Also, you are comparing the output against the original side-by-side - which is the most stringent test.  If you show a reproduction to someone without the original, would they point out the discrepancy in the color of the sky or the grass, or the blue of the eyes or the tone of the sepia.  If not, does it matter how close you are to the original?  I am not saying you should lower your standards, but are you trying to achieve the impossible?

Now about the idea that has occurred to me before (what is that saying...a little knowledge is a dangerous thing) but haven't tried to see for myself:  I am wondering since your final goal is to produce inkjet prints of the originals, why not "lump" the two separate profiles (one for the scanner and the other for the printer/paper) into a single unified profile that takes one straight to the print from the scanner.  The potential profiling process could go this way:  print the  i1Studio target, then instead of measuring those output patches, scan them without using scanner profile, take the file back to a non-color managed software (like ACPU) and print the patches again.  Now you run the i1 to create the combined profile.  Finally for the reproduction, take the scanned image directly to Photoshop and print with this combined profile.  Most likely I am overlooking the a pitfall or two in the process.  Just some food for thought!


:Niranjan.
 
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Doug Gray

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1. Given a hypothetically perfect paper profile: if printing an image using Absolute to two different papers that have a large enough gamut for the image, would the output look identical? I ask because even now that my paper profiles have dEs of around 1.0, there's still a visible difference in color temp between my test prints on different papers. They're very close, but I can tell that one looks warmer and the other colder.

They should look the same under the following conditions.

Use the same spectro to measure colors on the original as well as prints and use that same spectro when creating profiles for the paper. There are differences between spectros and using difference ones for measuring color and creating profiles is best for making reproductions. Differences are exacerbated when using an OEM profile on a paper with OBAs as it is unlikely to be an M2 profile and measuring colors with an M2 profile.

The prints should not have an unprinted border. If they do you will adapt to the white borders. This will cause the prints to look somewhat different even if the body of the print is colorimetrically the same.  If the originals have a border scan the complete originals including the border and trim the prints.

Texture can alter colors because the original and repro may reflect specular components differently. Spectros measure color that is reflected from light at 45 degrees. This minimizes effects of luster/glossy/matte surfaces but only if the objects are also illuminated at 45 degrees.

Beware of colors near the paper's max luminance. This is often an area where the paper is out of gamut with the image. For instance a paper with a white point of Lab(95 0 -2) can print Lab(95,0,0) quite well since only a slight amount of yellow is needed. OTOH, a paper with a white point of Lab(95,0,2) cannot because the mix of cyan and magenta needed to decrease b* will drop the luminance and you will get something like Lab(94,1,1) as it is out of gamut. Out of gamut colors are mapped to the closest gamut boundary.

Another issue with repro work occurs if the original has significant fluorescence. If so you will need to find a photo paper that has similar fluorescence if the prints may be viewed by window light or outside. However, you should still use M2 (uV cut) profiles because the scanner has little/no uV. Similar substrate fluorescence will do the best job of making the prints look close to the originals when viewed outside.
« Last Edit: May 12, 2018, 11:44:37 AM by Doug Gray »
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BrianToth

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Given that the original photographs would have been printed on a wide variety of papers each with its own texture, reflectivity characteristics, and base color, spanning decades in time and technology - would it not be practically impossible to reproduce them all on a couple of inkjet papers using a generalized workflow?


That was my original assumption. Once I standardized on using the ColorChecker images to test, and learned how to measure and compare my results (thanks to Doug), I realized I had a more basic problem on my hands. Now, I do suspect there could be some photos that a generic workflow won't apply perfectly to, but given the 100s that are here, I'm hoping that most will be "good enough". To compound the problem though, the originals that my family want reproduced the most are super deep glossy prints. They look pretty good printed to glossy paper, but of course there's a catch :) these photos have writing on the back that they want preserved too, so I had to limit myself to papers that supported printing on the back too… so I'm going to have to accept that my prints might have a different look if I'm using papers with different characteristics. I think I just need to stay away from any papers that are too different, otherwise I'll run into issues with smaller gamuts that would complicate matters more.

Also, you are comparing the output against the original side-by-side - which is the most stringent test.  If you show a reproduction to someone without the original, would they point out the discrepancy ….  If not, does it matter how close you are to the original?  I am not saying you should lower your standards, but are you trying to achieve the impossible?

I agree with all of this. :) I will say, I was about to give up many times, the learning process can be discouraging, and I'm often interrupted by actual work I need to do – this stuff is time consuming! I had things to where I would classify it as "acceptable" and at least better than amateur work but then I finally got my prints dialed in and now I'd say they're like 92% there! So now I'm quite excited that I might be able to squeeze out just that little bit more if I can get my scanning dialed in too. When I print the ColorCheckers, any difference side-by-side on different papers is imperceptible (to me) under normal lighting – aside from glossiness. If I hold them under different lights and squint I might be able to pick them apart. The ColorCheckers aren't a great stress test for clipping or other gamut issues (I don't think), but they've made a good practical test that's relatively easy for me to measure (now).

The prints should not have an unprinted border. If they do you will adapt to the white borders. This will cause the prints to look somewhat different even if the body of the print is colorimetrically the same.  If the originals have a border scan the complete originals including the border and trim the prints.

I did figure that out eventually. I didn't believe it could make that much of a difference, but I'm now in the habit of always cutting off the excess paper borders and it helps. They're close enough now that I sometimes mistake the prints for the original unless I'm really looking for it. So I'd say that's progress!
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Doug Gray

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I will say, I was about to give up many times, the learning process can be discouraging, and I'm often interrupted by actual work I need to do – this stuff is time consuming!

Discouraging, but ultimately rewarding.

I've always found I learn the most from what doesn't work. One gets to break it down to find the whys. The result is knowledge.
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BrianToth

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They should look the same under the following conditions. …

Looks like I'm now doing things correctly, given what I have to work with.

Beware of colors near the paper's max luminance. This is often an area where the paper is out of gamut with the image. For instance a paper with a white point of Lab(95 0 -2) can print Lab(95,0,0) quite well since only a slight amount of yellow is needed. OTOH, a paper with a white point of Lab(95,0,2) cannot because the mix of cyan and magenta needed to decrease b* will drop the luminance and you will get something like Lab(94,1,1) as it is out of gamut. Out of gamut colors are mapped to the closest gamut boundary.

Hopefully if I'm sticking with glossy papers with a large gamut that are relatively bright, my originals should hopefully fit within in the gamut of my new papers well enough for now. If/when I start branching out or bumping into related problems I'll need to come back to this. I understand it at a high level, would like to know it from a more detailed level some time.

Discouraging, but ultimately rewarding.

I've always found I learn the most from what doesn't work. One gets to break it down to find the whys. The result is knowledge.

I've learned a lot from your help in a short period of time. My early trial-and-error raised a ton of questions, now I have a direction and feel like I'm progressing. Quite a bit has been over my head (even in this thread), but that's fine because as I learn I can go back and absorb the things I missed the first time around. I hope once I get this project moving along a bit I can really dive into this subject even more and try to learn more of the technical aspects.

I think that right now, for all practical purposes, and given my current resources, I should probably consider my printing to be close enough and get on with the next step. :)
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BrianToth

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Re: Some questions about working with Absolute Colorimetric intents
« Reply #93 on: May 12, 2018, 06:26:29 PM »

STEP 2: Scanning


Now that I feel more confident that my printer output is on target, the next step is to look into my scanning. To try to keep things consistent and relevant with the previous discussions, my test photo is one of my printed ColorCheckers that I've already taken measurements of.

I'm not sure where I should begin as there's so many variables, but I think I'll start with some basic measurements and then break it down from there as necessary?


Test Input
  • Source photo is the same BabelColor ColorChecker TIFF in native Lab color space that I've been using throughout my testing.
  • I have Photoshop's color settings set to absolute colorimetric.
  • I printed the ColorChecker to Canon Photo Paper Plus Glossy II using an absolute colorimetric intent and a custom profile that I've recently made using i1Studio.

Scanner profiling
  • I have multiple options for profiling targets: I have a Digital ColorChecker SG (DCCSG), 3 IT8 reflective targets, and a ColorChecker 24 Mini. (I'd love to try making my own reference files, but frankly it's a pain doing spot-checks with the i1Studio unless the color area is large enough
  • For software I have: Epson Scan, VueScan Pro, and SilverFast 8. (Let's forget I mentioned SilverFast unless it can work miracles.)
  • For doing the profiling I have i1Studio and Argyll CMS.

Process
  • Scan target using Epson Scan set to "No Color Correction" which disables everything. Output as 48bit untagged TIFF.
  • Create profiles with i1Studio and Argyll.
  • Scan my printed ColorChecker in Epson Scan using the exact same settings.
  • Open the untagged TIFF in Photoshop and *assign* the profiles.
  • Record the Lab values from the info panel

Findings

i1Studio doesn't give me any diagnostic output. But with Argyll I can run profcheck to output dE values of the profile vs the target reference values:

Argyll -aX -qu DCCSG: Avg dE(76) = 0.64, max dE(76) = 2.8.
Argyll -aX -qu DCCSG: Avg dE(2000) = .45, max dE(2000) = 2.17.

Argyll -aX -qu IT8: Avg dE(76) = 0.64, max dE(76) = 2.8.
Argyll -aX -qu IT8: Avg dE(2000) = .21, max dE(2000) = 1.52.


Things get a bit messy when I apply the profiles to the scanned image of the ColorChecker though:

Argyll -aX -qu DCCSG: Avg dE(76) = 3.9894, max dE(76) = 10.806.
i1Studio DCCSG: Avg dE(76) = 3.925, max dE(76) = 9.555.
Argyll -aX -qu IT8: Avg dE(76) = 3.117, max dE(76) = 7.451.

(The avg and max don't really tell the whole story so I attached the individual color values and dEs.)

Over the last few months I've done a lot of reading about scanning. I understand the basics that scanners see differently than people or spectrophotometers, and different papers being scanned can lead to different results. But I have a feeling that I should be able to achieve better results that I am. If not, please let me know. I'd be curious if anyone's done similar testing and what kind of results you achieve.

I also get different results if I start with different scan settings. For example if I go with a VueScan 48bit RAW vs 24bit RAW vs Epson Scan. Given the shear number of combinations between settings and profile creation, I'd love to find a way to streamline my testing process. (Or if someone can just tell me what's best! Ha.) For example, when I use Argyll I have a script to output every combination of profiles, output profcheck results, and output TIFFs with embedded profiles all in one go. If I could take the RGB color values of my Epson Scan scan (attached) and run them through each profile that I create (including the X-Rite profiles) using some command line tool that would be great. I tried using a couple Argyll tools, but probably used them wrong as the output seemed like nonsense.

So, much like my printing analysis, I'd like to know if my testing is sound, if I should be able to achieve better results, and if so, the most efficient way that I can test so that I can ask smart questions and not waste too much time. :)

Thanks!
« Last Edit: May 12, 2018, 06:33:59 PM by BrianToth »
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BrianToth

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Re: Some questions about working with Absolute Colorimetric intents
« Reply #94 on: May 12, 2018, 06:57:12 PM »

Looks like I found an answer to one of my questions. If I want to convert my scanned RGB values to Lab through a profile, it seems I can use icclu (part of Argyll). I had tried it before, but I was missing the scale parameter.

Quote
# Convert color list

input_colors="Epson Scan Scanned RGB.txt"
output="Results"
profile="_Epson v800 DCCSG Epson Scan 2018-05-11 QU (XYZ cLUT M+S) -aX.icc"

icclu -s255 -ff -ia -pl -v2 "$profile" < "$input_colors" > "$output Forward Absolute Lab.txt"
icclu -s255 -ff -ir -pl -v2 "$profile" < "$input_colors" > "$output Forward Relative Lab.txt"
icclu -s255 -ff -ip -pl -v2 "$profile" < "$input_colors" > "$output Forward Perceptual Lab.txt"

Aside from very minor variations the results match up with what I see in Photoshop's info panel and correspond to the intent I choose in Photoshop's color settings. I could whip up a program to take the output and run it to a spreadsheet. It'd be great to find a way to automate the dE calculation between the results and the original.
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Doug Gray

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Re: Some questions about working with Absolute Colorimetric intents
« Reply #95 on: May 12, 2018, 10:48:13 PM »

Looks like I found an answer to one of my questions. If I want to convert my scanned RGB values to Lab through a profile, it seems I can use icclu (part of Argyll). I had tried it before, but I was missing the scale parameter.

Aside from very minor variations the results match up with what I see in Photoshop's info panel and correspond to the intent I choose in Photoshop's color settings. I could whip up a program to take the output and run it to a spreadsheet. It'd be great to find a way to automate the dE calculation between the results and the original.

You might want to start a new topic on profiling scanners. It's a fairly complex area because there is little to no info on the spectral characteristics of the light profiles use to scan. The same problem applies to cameras. It's a specialized art. Long ago I made scanner profiles but don't currently have a good scanner. There are people here that have done significant work with scanners.

Also, you might want to look into getting Matlab for processing files. They have a low cost version for non-commercial home use. It's really hard to beat. I use it extensively for working with images, CGAT files and such and have made scripts and functions that calculate dE76 as well as dE00. It think Matlab and the Imaging toolboc can be had for about $200. Would be happy to share these with you if you take the plunge.
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digitaldog

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Re: Some questions about working with Absolute Colorimetric intents
« Reply #96 on: May 13, 2018, 12:27:26 PM »

Unlike some camera profiles, scanner ICC profiles are easy to make and are effective. The target plays a role (the gamut of the scanner profile can't exceed the target for one). Scanners and cameras don't really have a color gamut. At least some scanners with software that support profiles allow an idealized behavior of the data with controls over the rendering of the scan into either the scanner RGB or to some RGB working space. Output referred,one light source, so much simpler than a camera.
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Andrew Rodney
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Doug Gray

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Re: Some questions about working with Absolute Colorimetric intents
« Reply #97 on: May 13, 2018, 12:50:46 PM »

Unlike some camera profiles, scanner ICC profiles are easy to make and are effective. The target plays a role (the gamut of the scanner profile can't exceed the target for one). Scanners and cameras don't really have a color gamut. At least some scanners with software that support profiles allow an idealized behavior of the data with controls over the rendering of the scan into either the scanner RGB or to some RGB working space. Output referred,one light source, so much simpler than a camera.
Scanner profiles are almost always scene referred, not output referred, since they are used to replicate images that don't have the dynamic range of typical photos which look better output referred.
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nirpat89

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Discouraging, but ultimately rewarding.

I've always found I learn the most from what doesn't work. One gets to break it down to find the whys. The result is knowledge.

Agree wholeheartedly.
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