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Surgical-accurate, freeware color management

I’ve been experimenting with some freeware tools for color management. Anyone who ever used this sort of software knows that they are kind of rustic and demand its users some advanced skills beyond simple keyboard and mouse operation and the on/off switch location. But this extra effort usually pays off. Here is a case.

argyllcms_testThis photo shows certain package, from which I took a measure of the yellow patch, and after the procedure described below I printed it on an inkjet printer. This image seems to show an almost perfect match, and indeed it is: Yellow patch on the box has Lab coordinates equal to L* = 76.26, a* = 22.85, b* = 83.97; printed yellow is L* = 75.86, a* = 21.26, b* = 86.30. ΔE 2000 between them is barely 1.33!

The full procedure took no more than 40 minutes y required just one try. This tool has a place reserved in the mount Olympus of Color Management…

The tool: Argyll CMS (www.argyllcms.com), an open-source freeware tool introduced as “an ICC compatible color management system, available as Open Source. It supports accurate ICC profile creation for scanners, cameras and film recorders, and calibration and profiling of displays and RGB & CMYK printers”. Chosen application: creating an ICC profile out of an Epson Stylus Pro 4900 inkjet printer. The purpose: a color proof with no RIP. Is such a thing possible?

Short answer: YES. All we need to know is how to set up color management options in the print dialog of typical applications, and an accurate ICC profile of our printer. Here is where Argyll CMS does its magic. As a helper tool I also used Little Argyll GUI (www.russellcottrell.com/photo/LittleArgyllGUI.asp), a small user interface freeware to Argyll. Little Argyll GUI requires Argyll CMS to be already installed, so I downloaded both and installed them.

Creating the profile

Little Argyll GUI is a single-window application with several tabs, one of them is for printer profiling. The software lists to us the required steps:

  1. Define a color chart: I chose a 924 patches chart, including 51 grayscale patches (0 to 100% in 2% steps). This operation gives us a reference text file containing our chart definition.
  2. Create the chart image file: One or more TIFF files are created according to number of patches, available paper size and measurement device. In my case I used an X-Rite i1 spectrophotometer and A3-sized paper. In this particular conditions the program created just one TIFF file.
  3. Printing the chart: I printed that file from Photoshop directly to my printer, with all color management options disabled (otherwise we will not be able to measure our printer in its “pure”, unmanaged state). This chart is the one you can see printed in the picture, under the big yellow printed patch.
  4. Measuring the chart: After enough drying time, I measured the chart in strip mode, the fastest available when you don’t have an automated table. A measurement text file is created.
  5. Building the profile: From that file an ICC profile is created. Argyll CMS not only builds the profile but evaluates it and computes its precision as well.

Last step is testing this newly created profile. To make it available to your installed applications you have to copy this file into the profile’s system folder, i.e.  C:\Windows\System32\spool\drivers\color on Windows or /Library/ColorSync on Mac.

The moment of truth

In Photoshop I created a new document in Lab mode, filled it with a Lab color equal to 76, 23, 84 (Photoshop limits Lab values to integres, so those are the closest ones to the target color) and converted to RGB by means of Convert to Profile… with the following parameters in advanced mode:

  • Destination space: RGB;
  • Selected profile: The one we have just created, obviously.
  • Engine: Adobe ACE
  • Intent: Absolute Colorimetric
  • Use dither: Disabled.

After that, I printed the resulting RGB image with no color management whatsoever (I’ve already done that when converting). You can see the results.

A color proof with no RIP

Although it is not a straightforward procedure, it shows how to print contract color proofs with no RIP. There are two ways:

  • You can convert an image (you may need to convert it to an image first if it is a PDF, for instance) from its color space to RGB using Convert To Profile and then print it with no color management options neither in your application nor in the printer’s driver;
  • You can print your document directly but setting color management options accordingly in your application, choosing the created profile as the printer’s (and also disabling those options in the printer’s driver, so color will not be converted twice). This way color management is done just at print time, with no need to modify your original document.
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