Suggestions on checking outsourced printing profile quality.

[Doug Gray]

RHPS's post about printing a color strip along one edge of a photo to check when he needs to get new profiles made me think about how this could be done when using outside printers. Ideally, one should print color strips that would match when adjacent to a colorchecker card. But this will not happen unless you print the image in Abs. Col. Intent and that is rarely appropriate for printing pictures. When you print a Colorchecker image in Perceptual or Relative it is altered in various ways and will not match an actual card.

But there is a way by round tripping a colorchecker image. You can create a new image that, when printed in PI or RI will come out looking exactly like a colorchecker card. You have to create 3 different images, one each for Relative Intent, Relative Intent w BPC, and Perceptual Intent.

Here's the recipe in Photoshop (not possible in LR):

Assume we have a profile named "E9800Luster" To create an image that can be printed using Perceptual Intent:

• Start with a Colorchecker image in Lab colorspace.
• Convert to printer space using the printer profile and selecting Absolute Colorimetric conversion.
• Then Convert back to Lab using Perceptual Intent.

Save the created image as CC_Perceptual_E9800Luster.tif

Do the same steps for Relative and Relative w BPC but, in step 3, change use "Relative" or "Relative w BPC" and label appropriately.

Now you have three different images that can be printed alone or spliced into another image that you will print. Just select the one to match the printed intent you will choose when sending the image out. When you get the prints back just compare the printed CC with an actual CC.

[BradFunkhouser]

That profile "E9800Luster" has been provided by the outside printing service and is the one they'll use when making prints for you, correct?  And all the Colorchecker patches need to fit inside that printer space.

So, just thinking about perceptual intent... after your absolute out/perceptual back round trip, you end up with color patch values in Lab that, when subsequently mapped perceptual back into printer space, should result in printer device values that produce measurably close D50 absolute matches to the physical colorchecker patches.

Interesting idea.  Thanks.

[Doug Gray]

That profile "E9800Luster" has been provided by the outside printing service and is the one they'll use when making prints for you, correct?  And all the Colorchecker patches need to fit inside that printer space.

Yes, for instance if you use a Costco printer that you can download a profile for and submit an image in device space then this would be a good way to check their color management. For glossy and luster type surfaces CC patches are within gamut except possibly for the white patch. The paper white has to be at or above the white patch or it would print somewhat off. The other patches should be in gamut. For Matte prints several of the patches may be out of gamut depending on the printer's capability. Easy way to check that  is to use Abs. Intent in step 3. Then compare it to the original CC image.

So, just thinking about perceptual intent... after your absolute out/perceptual back round trip, you end up with color patch values in Lab that, when subsequently mapped perceptual back into printer space, should result in printer device values that produce measurably close D50 absolute matches to the physical colorchecker patches.

Interesting idea.  Thanks.

Exactly. It gets around the problem Perceptual has. Perceptual Intent color mapping is completely up to the profile maker but has one important requirement. It is reversible. This technique takes advantage of that reversibility.