[Lopez Carlos Participant Posts: 1]

Printing Colour Management

on: November 12, 2023 at 4:31 pm

Hello, I’m creating the printer profiles with IProfiler and argyll. I would like to know if it exists a program like Oris Certified Proof but for RGB. I used this app in the past to certify my proof was ok with ISO standards. Is there any app? Oc can i do with IProfiler or argyll ?

Thank You

Is there a better way than doing like this? This is my theorethical proof, but i would like to use with a printed chart.

 

Here’s details on my calls to ArgyllCMS:

targen -v -d2 -G -e2 -B 2 -g64 -f210 validate

printtarg -v -i CM -h -T300 -pA4 validate

cctiff -ia .\sRGB.icm .\i1_1xa4.icm .\validate.tif validate_abscol.tif

(or use -r for relative colorimetric)

chartread -v -T “0.4” validate

profcheck -v -k -s -I r .\validate.ti3 .\printerprofile.icm

[Andrew Rodney Participant Posts: 351]

Re: Check accuracy ICC printer profile

Reply #1 on: November 12, 2023 at 4:46 pm

So, there are several 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, that 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 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.

 

Author “Color Management for Photographers" & "Photoshop CC Color Management" (pluralsight.com)”

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