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Home » , » RawTherapee cross-platform raw image processing program: a color-managed Linux workflow (Chapter II).

RawTherapee cross-platform raw image processing program: a color-managed Linux workflow (Chapter II).

The default illuminant is D50; D55, or 5500°K, is not provided as an option.  The spectral data in Argyll’s own custom spectrum file, D50_1.0.sp, can be found in Measuring Colour, Fourth Edition [PDF] by R.W.G. Hunt and M.R. Pointer, conveniently accompanied by the values for D55. 

I used the latter to create D55_1.0.sp.  (Note, page 358 contains a typo; the middle columns for wavelengths 785+ are misaligned, and should be under D50, D55, D65, and D75.)

One more step remains before using the profile for high-quality work:  determining output levels as described on the BTDZS workflow page.

For printing real images, the only differences are that the image will have an embedded working space profile, and we set the printer profile in the color management dialog.  (I also set the soft-proofing display mode.)  Everything else stays the same.

PhotoPrint settings for actual printing:

rawtherapee -photoprint 0.4.2-pre2

 color management

The final result.  This print is something of a worst-case scenario, using Office Depot High Gloss paper and Amazon.com bargain ink profiled as above.  The profile clearly works, although the blues are a little off:

Prints made with and without the printer profile.

composite

TurboPrint.

Is there any other way to print in Linux with a printer whose manufacturer has not provided a driver?  The proprietary application TurboPrint comes with drivers for many more printers than Gutenprint does.  Additionally, they include things like ink levels and head maintenance, which is essential for higher-quality printers.  Unfortunately, PhotoPrint does not work with TurboPrint.  The latter does come with a GIMP plugin, which in that case limits it to 8 bits (GIMP 2.9, under development, may finally use 16 bits!)  CinePaint and Krita are both color-managed and 16-bit; the former does not print with TurboPrint; the latter does, but its printing is buggy, as it does not seem to be able to distinguish the image size from the page size.  RawTherapee is 16-bit but, unfortunately, has no printing capability.  (In reality, 16-bit is superior for image editing, but probably not really necessary for printing the final image; color management is much more important.)

So all things considered, I gave TurboPrint and GIMP a try.  I downloaded and installed the former from turboprint.info without any problems.  It comes with a fairly thorough .pdf manual.  You need to add your printers to TurboPrint; they will be named things like iP3000-TurboPrint and Pro9500II-TurboPrint so you can identify them.  Then comes profile creation.  TurboPrint’s “printer profiles” are actually media presets to which you assign an .icc profile.  After naming a new profile and choosing the paper and dpi resolution, the application offers to print a row of test images that will allow you to set an ink limit; it’s an interesting touch.  The default is 250; I found 175 to be plenty.  The type of paper and ink are also specified in the profile.

Before and after importing the .icc profile:

printer profile printer profile

At this point, the .icc profile has not yet been created.  The “printer profile” is unmanaged, and we will use it to print the patch targets.  For the Pro9500 Mark II, I made a two-sheet target.  This one uses relatively more grays:

targen -v -d2 -G -e4 -B4 -s32 -g64 -f924 Pro9500II_CanonSemiGloss

This time, we are going to create an 8-bit target image for GIMP (the lower-case -t):

printtarg -v -ii1 -t 300 -C -p Letter Pro9500II_CanonSemiGloss

Amazingly, TurboPrint supports other media besides plain paper!  In GIMP, one prints with it via File — TurboPrint.  The media type/paper is the printer profle that you created.  All details of the configuration must be kept the same every time, including resolution (which does not always default to that built into the profile) and dithering.

TurboPrint must be told the print’s color space, which means that almost anything other than sRGB must be installed via the Control Center.  But in this case, there is no destination profile, so the source space is ignored even though one is specified on the main panel (the Color tab in the configuration menu, which also specifies the source space, is grayed out).  Be sure to properly scale the image.  This is how we print our unmanaged profiling target:

TurboPrint

chartread -v Pro9500II_CanonSemiGloss
colprof -v -D "Pro9500II Canon Semi-Gloss" -qh -i D55_1.0.sp -S ProPhoto.icm -cmt -dpp Pro9500II_CanonSemiGloss

Read the patches in the usual way.  Once you have created the .icc profile, go back to the Control Center, open the printer profile, and import color data in the form of the .icc file.  The profile status will now be “complete” and ready for color-managed printing.  In GIMP, one prints in the same way, except that now there is a destination profile which needs a source color space.  In this case, the unmanaged print made on Canon Semi-Gloss was not too far off:

Prints made with and without the printer profile.

composite

Sounds good so far . . . .  Now for the thorns among the roses.  There were a few major kinks in the TurboPrint workflow.  When printing with the iP3000, the printer installation twice became corrupted; TurboPrint’s print dialog in GIMP all of a sudden had a button that said “Gutenprint Config” instead of “TurboPrint Config,” and a number of the other controls had disappeared.  I had to uninstall then reinstall the printer with a different name to get it to work again.  More seriously, the Pro9500 Mark II would only print one print at a time, after which the blue light would blink and it would neither print nor shut down.  The TurboPrint status monitor would say things like, “Timeout - communication to printer broken,” then “Printer status failed - no access,” then “Printer not connected or switched off” (it wasn’t).  I had to unplug the printer and plug it back in to get it to print again, which means it had to go through its maintenance cycle EVERY SINGLE TIME.  None of the inks started out low, but I had to replace three inks after printing several sheets of test images and a two-sheet profiling target.  Needs work . . . .

failed

At the expense of more ink, I made a few borderless 8.5×11’s with the Pro9500 Mark II, and the quality was amazing; the colors and values were pretty much dead-on, a tribute to Argyll’s monitor and printer profiles.  I then switched to Windows 7 and made some more prints using the new .icc profile with Photoshop and Canon’s driver; there was an obvious difference between these and the former prints, and between print and monitor, indicating that the .icc profile should be considered specific to the driver.  (Argyll’s monitor profile seems to work just as well in Windows; it’s the same graphics card.)

party

There you have it.  We have plenty of room to grow here; the biggest need at present is printer drivers and 16-bit color-managed applications to run them.  But the bottom line is, let there be Linux!

Beyond

Argyll is available for Windows and Macintosh as well.  Because of the need for new Windows USB drivers for some measurement devices, and because the Linux command line seems more friendly in general, it may still be easier to use the program in Linux even when profiling a Windows or Mac computer; one simply does the printing with the manufacturer’s driver and Photoshop, for example, and does everything else in Linux.  Here are the commands for generating a 24×11-inch i1Profiler target:

targen -v -d2 -G -g257 -f1491 iPF6350_IlfordGPGFS
printtarg -v -ii1 -T 300 -C -p 609.6x279.4 iPF6350_IlfordGPGFS

Why we don’t use AdobeRGB anymore

gamuts

The wire mesh is the Adobe RGB gamut, and the solid figure is Ilford Prestige Gold Fibre Silk on the Canon iPF6350.

iccgamut -v -ff AdobeRGB1998.icc
iccgamut -v -ff GPGFS13_CANipf6350_PSGP280n.icc
viewgam -v -cw -w AdobeRGB1998.gam -cn -t 0.0 -s GPGFS13_CANipf6350_PSGP280n.gam -n ipf6350.wrl

Get Cortona3D Viewer to view the .wrl VRML file (unfortunately, Windows only; OpenVRML doesn’t seem to be available anymore, and I couldn’t get FreeWRL to work).

Straying from the topic

How to add 90° rotation viewpoints to the .wrl file:

Viewpoint {
  position 0 0 360      # Position we view from in x, y, z; adjust the distance based on the size of the plot.
  orientation 0 1 0 0   # Axis in x, y, z, and rotation in radians; 0 1 0 is the vertical (y) axis.
  description "L*"
  jump FALSE
}
Viewpoint {
  position 360 0 0
  orientation 0 1 0 1.57
  description "a*"
  jump FALSE
}
Viewpoint {
  position 0 0 -360
  orientation 0 1 0 3.14
  description "-L*"
  jump FALSE
}
Viewpoint {
  position -360 0 0
  orientation 0 1 0 4.71
  description "-a*"
  jump FALSE
}
Viewpoint {
  position 0 0 360
  orientation 0 1 0 0
  description "L*"
  jump FALSE
}

See it at ThreeGamuts.htm.

How to make a black wire mesh:

appearance Appearance {
  material Material {
    transparency 0.500000   # adjust as desired
    ambientIntensity 0.3
    shininess 0.5
    emissiveColor 0.000000 0.000000 0.000000   # black
  }
}

See it at RussellRGB.htm. scaled

Why do these gamuts look like flat biscuits?  Because the a* and b* axes are 255 units wide, but the L* axis only goes from 0 to 100.  To make the axes equal, one may scale the first two members of each of these point positions, for every gamut in the .wrl file, by 100/255 (and then adjust the viewpoint position accordingly):

coord Coordinate {
  point [                   # Verticy coordinates
    -2.755150 116.556000 41.480600,
    1.140780 113.852000 39.407000,
    10.895100 107.094000 34.211500,
    . . .

This actually makes them look too enlongated the other way; maybe an intermediate scale factor would look better.  I will leave this one to you.

Resources

D55_1.0.sp, a custom spectrum file for specifying the D55 (5500°K) illuminant when using colprof to create a printer profile.

ProPhoto2255 RGB, the ProPhoto RGB working color space with gamma set to 2.2 and white point to 5500.

Generating custom Argyll Color Patches.

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