Print Service ICC Profiles

[Doug Gray]

Thanks, that indeed works, but does exactly the same thing with more precise read-out. Still no softproof values - only picks up the values without softproof.

Yep. You can only get precision fractional numbers for the device (RGB values) in soft proof viewing. To get the actual proof Lab values you have to do a profile conversion to the device space. Then the first column will show the proof values in Lab as per my posted image.

As for colorimetric and black point rendering, the global color settings control that. For instance, if you want to see the actual printed color w/o having it adapted to paper white you just set the global color settings for absolute colorimetric. After doing that the L values will change when your image is in printer space. Much like setting view paper color in the view proof dialog changes the screen image.

Also, the global color settings affect readouts depending on black point settings and will scale the readout if it's selected. This can mess up proofing. Especially on matte paper.

[Mark D Segal]

OK, this is useful, but awkward! One thing though - in testing for the rendition of the actual colour, the target should be printed in Absolute Colorimetric RI, as you say; but this has a more pervasive effect than only on the L* channel.

[Doug Gray]

OK, this is useful, but awkward! One thing though - in testing for the rendition of the actual colour, the target should be printed in Absolute Colorimetric RI, as you say; but this has a more pervasive effect than only on the L* channel.

Awkward it is. Doable but awkward. I mostly stick to Matlab for that reason and occasionally cross check. I believe Argyll has some utilities that do similar conversions on the command line but I haven't used them. Matlab is very user friendly for going into the weeds.

And yes, rescaling Rel Col, which adapts Lab values to paper white, also changes a* and b*. The amount is greater when the paper white isn't neutral.

As a side note, One of the selectable profiles I have on the monitor is 100 nits and D50.  This makes it easy to read a Lab color directly off the screen. I also prefer D50 as a target as I find D65 much too bluish. D55 isn't bad for day to day work. It approximates paper white on OB laden papers but for precision work I will use D50 and soft proof with paper white selected which produces similar results with OB papers.

[Peter_DL]

After emailing, live chatting, and phone calling - the range of answers from Costco to some very high priced labs resulted in this range of results:

There are a bunch of labs who will tell you to send them any file format, any color space, etc.  They infer that they are fully color managed.  When it got down to it, the "front end" of their process converts everything they receive into sRGB jpegs for printing.

One lab proudly offers a single ICC profile for use with any of their paper selections.

Some want the file with the provided ICC profile used for soft proofing.

Other labs clearly tell you to soft proof to the ICC profile but to send them the soft proofed file in ProPhoto or Adobe RGB.

What I ended up telling the class is to do their homework with any lab, not to believe what the web site says, and that like John Arbuckle, "You get what you pay for."

Interestingly enough, Costco provides ICC profiles for each of their paper/printer combinations, and it is "by store location" specific and they are updated as needed.

Yes, there are different ways how the labs actually proceed regarding color management. Even, one and same lab may offer different ordering and processing paths.

Let's assume that the lab offers an ICC profile for download, from what I can tell there are two basic cases: either the lab operates the printer in a so-called "sRGB-mode", or they make use of the printer's full gamut.

This can be tested by providing a file with rich colors in ProPhoto RGB, and a variant thereof converted to sRGB, provided that both images are noticeable different on screen when arranging them next to each other, softproofed to the printer profile. Then, if the print from ProPhoto RGB is equal or worse than with sRGB, forget it, look for a different lab.

That way I checked out a bunch of labs in my region, found the right one, and against my concerns I'm quite happy with the "softpoof but do not convert approach".

Peter

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[Doug Gray]

Yes, there are different ways how the labs actually proceed regarding color management. Even, one and same lab may offer different ordering and processing paths.

Let's assume that the lab offers an ICC profile for download, from what I can tell there are two basic cases: either the lab operates the printer in a so-called "sRGB-mode", or they make use of the printer's full gamut.

This can be tested by providing a file with rich colors in ProPhoto RGB, and a variant thereof converted to sRGB, provided that both images are noticeable different on screen when arranging them next to each other, softproofed to the printer profile. Then, if the print from ProPhoto RGB is equal or worse than with sRGB, forget it, look for a different lab.

That way I checked out a bunch of labs in my region, found the right one, and against my concerns I'm quite happy with the "softpoof but do not convert approach".

Peter

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Peter,

For houses like WHCC which offers "profile only profiles" but allow you to tag images with any matrix based profile like sRGB, aRGB or ProPhotoRGB, and assuming they are properly color managed, there remains one problem. One that Andrew pointed out earlier. They may, like WHCC, not let you select rendering intent. Presumably, they expect you to use Perceptual when soft proofing but what if you want Relative Intent?

One way to get around this, which works but is a kluge, is to convert your image to the soft proof profile they provide using the desired intent, then convert back to an RGB space such as ProPhoto or Adobe using Rel Col. w/o BPC Then, the RGB values in the image will print the rendering intent you want when printed by their printer in PerRI.