Luminous Landscape Forum
Raw & Post Processing, Printing => Colour Management => Topic started by: Dinarius on April 01, 2024, 05:35:46 am
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Delt.ae left the building recently. (Unless it's available at a new link I'm not aware of... ::)
Any suggestions for alternatives to it for testing colour profiles?
Thanks.
D.
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Just found these.........
https://heritage-digitaltransitions.com/are-you-sure-youre-fadgi-compliant/
https://www.digitizationguidelines.gov/guidelines/digitize-OpenDice.html
Anyone using OpenDice?
Thanks.
D.
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So there are a number of ways to tackle this depending on what you're looking to judge.
One simple way is to simply compare the reference values that created the target to the measured values of the target run through the printer. But that only provides an overall accuracy report, not specifics. But the idea is, you've got an RGB value that's a reference and an RGB value from the measurement of the target itself. Conduct a dE report in ColorThink.
But here's a way to test the differing tables (it's kind of complicated). We'll use a target we call 216pixel_RGBs.tif as an example, use the iStar or whatever patch set you wish where 1 pixel is one color patch:
1. Open the "216pixel_RGBs.tif file in Photoshop. This file needs to be kept exactly as it is (individual pixels). Duplicate the file. Size the image using Nearest Neighbor to an appropriate print size. Call this "Reference Print File". You'll print this out and measure.
2. Print this file out to the profiled printer. (You're sending the RGBs in the file to the printer.)
3. Let the print stabilize, and then measure it and save the data as "Reference Labs.txt". The 216 RGB.TXT file (a reference file that built this target) needs to be installed for MeasureTool or PatchTool or whatever software you'll use to access access the data. This data measured is the bottom line -- what happens when you send these RGBs to this device.
4. Now you need to create predicted Lab files from the RGB. You need two versions -- one in pixels to compare in ColorThink, one upsampled to print -- for each profile.
5. Take the RGB pixel file and Assign the printer profile. Convert Abscol to Lab. Save the results with the profiling package somehow identified in the filename (eg "i1P 288 Luster/Predicted"). I suggest saving the pixels versions as ProfilePackageName Predicted Labs.
6. Take the upsampled RGB file. Assign the printer profile. Convert Abscol to Lab. Convert from LAB to printer profile being tested using absocl and print.
7.Let the print stabilize and measure the results. Save the measurements as ProfilePackageName Roundtrip Labs ("i1p 288 Luster Round Trip"). You now have three things to compare for each package: A. The Reference File ("Reference Labs.txt"). The Predicted Labs ("i1P 288 Luster"). The Roundtrip Labs ("i1P 288 Luster Round Trip"). B. Reference-to-Predicted ("Reference Labs.txt"/"i1P 288 Luster") shows you the accuracy of the AtoB Colorimetric table. C. Predicted-to-Roundtrip ("i1P 288 Luster"/"i1P 288 Luster Round Trip") shows you the accuracy of the BtoA Colorimetric table. Reference-to-Roundtrip ("Reference Labs.txt"/"i1P 288 Luster Round Trip") gives you a decent measure of the overall profile accuracy. You'll typically see that the AtoB and BtoA errors tend to cancel each other somewhat because they go in opposite Directions-Reference-to-Roundtrip shows that nicely.
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Andrew,
Thanks for that and I may use it.
But, I should have made it clear that I'm trying to find a way of testing camera colour profiles (created using Lumariver) which I used to test using Delt.ae.
OpenDice looks like an option, but I can't get it to install. I've been in touch with them about the issues. Hope to resolve it as it looks like an alternative.
D.
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Cameras? Kind of pointless but good luck.
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Delt.ae left the building recently. (Unless it's available at a new link I'm not aware of... ::)
Any suggestions for alternatives to it for testing colour profiles?
Thanks.
D.
Icc or dng camera profiles ?
Scene referred profiles or multi-purpose profiles ?
For multi-purpose profiles you might want to check/compare with profiles made by raw converter on a small bank of raw. Check for color transitions, color quantization, skin tones separation, from flat scenes to HDR scenes, from sunlight to various lowlight illuminants, check gamut compression on strong colors light as color tubes, especially if you intend to use it for any illuminant you encounter.
Check Highlights too if there is no shift in colors near saturation as hueshifts due to a channel clipping.
You can also check the grey linearity too, with images, and/or colorthink pro for icc.
By experience, on some raw converters, some icc camera profiles made by manufacturers can have some defect sometimes on some specific cameras, but generally, they know what they do, especially Adobe.
for scene-referred profiles, some of these checks are not necessary. A good workflow or scene reference is to double-check the profile made with a chart on another chart with different color patches/reflections (glossy/mat, etc) if you plan to use it with different surfaces to reproduce. These profiles are generally more critical in terms of DE tolerances, so they can introduce more artifacts as color quantization on 3d scenes or for a general purpose. Moreover, they are generally mono-illuminant.
Lumariver is a pretty good profiler, but the options are not very intuitive. Overall profiles tend to be very qualitative.
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Icc or dng camera profiles ?
Scene referred profiles or multi-purpose profiles ?
For multi-purpose profiles you might want to check/compare with profiles made by raw converter on a small bank of raw. Check for color transitions, color quantization, skin tones separation, from flat scenes to HDR scenes, from sunlight to various lowlight illuminants, check gamut compression on strong colors light as color tubes, especially if you intend to use it for any illuminant you encounter.
Check Highlights too if there is no shift in colors near saturation as hueshifts due to a channel clipping.
You can also check the grey linearity too, with images, and/or colorthink pro for icc.
By experience, on some raw converters, some icc camera profiles made by manufacturers can have some defect sometimes on some specific cameras, but generally, they know what they do, especially Adobe.
for scene-referred profiles, some of these checks are not necessary. A good workflow or scene reference is to double-check the profile made with a chart on another chart with different color patches/reflections (glossy/mat, etc) if you plan to use it with different surfaces to reproduce. These profiles are generally more critical in terms of DE tolerances, so they can introduce more artifacts as color quantization on 3d scenes or for a general purpose. Moreover, they are generally mono-illuminant.
Lumariver is a pretty good profiler, but the options are not very intuitive. Overall profiles tend to be very qualitative.
Scene referred.
Delt.ae was convenient in that it gave a star rating of the profile compatible with FADGI star ratings.
But, I agree that it's not really that necessary to check it if you've used Lumariver properly.
I would like to try OpenDice, but I can't get it to install on my system. Waiting to hear from them on this.
Thanks.
D.