Re: Workflow for ‘remote’ profiling a non-colormanaged printer as a ‘back-box’
Re: Workflow for ‘remote’ profiling a non-colormanaged printer as a ‘back-box’
- Subject: Re: Workflow for ‘remote’ profiling a non-colormanaged printer as a ‘back-box’
- From: G Mike Adams via colorsync-users <email@hidden>
- Date: Thu, 15 Jul 2021 10:24:15 -0500
Peter,
> One of our staff is using an external non-colormanaged print provider. And
> I'm wanting to help him prepare work for it. Test prints to this printer are
> in AdobeRGB1998 and prints come out over saturated.
First question would be if they look as if they have a profile applied to them
at all. If the machine is a grand format RIP-driven printer, and you send it a
file in any RGB colorspace, it’s pretty obvious to see if there’s an ICC
profile applied or not. Neutral grey, for instance, will print as black only
with no profile applied in this condition, whereas with an improper profile
applied it will print in CMY or CMYK and typically have some kind of obvious
color cast.
> So I am attempting to profile the print process ‘remotely’ using i1 profiler.
> And to do the color conversion ourselves.
> I am familiar with profiling inkjet and laser printers where I work using
> i1Profiler, FieryXF and ColorBurstRIP.
> I thought it would be a fairly straight forward process, but I’m getting some
> unexpected results.
>
> I am not in a position to control this external printer in any way.
> I have already had TC918 RGB patches printed on this printer (patches
> assigned AdobeRGB1998) and I created a printer RGB ICC profile of this
> process.
> When I assign this printer profile to the original AdobeRGB1998 test image we
> printed I get a very good approximation of the over saturated test print we
> got. So far so good.
>
> So I Imagined I just needed to use Convert-to-Profile on our AdobeRGB1998
> test image, to convert it into the printer color space that I built. Then to
> ensure it gets handled by the external printer in exactly the same way as
> before, I just assign it AdobeRGB1998 again.
That’s one of those things that sounds like it might work, and kudos to you if
you managed to get a passable result… but you didn’t. There are so many
variables involved though, that chasing them down now isn’t really an effective
use of time. Why don’t you or your staff member simply call them and ask some
questions?
> When I do that, the test image now appears less saturated than it was before.
> Great, that’s just what I would expect. With the boost of saturation of this
> print process it should return back to normal when printed.
Note that the responder that said that might be because the printer was
assigning sRGB to your Adobe 1998 file has that backwards. Assigning a smaller
colorspace to an image created in a larger colorspace results in a desaturated
image. Assigning a larger colorspace to an image created in a smaller
colorspace results in over-saturation. Adobe 1998 is, of course, a larger
colorspace than sRGB.
Even sending Adobe 1998 though, it could be possible for the RIP to be
assigning a larger colorspace. If the printer is doing something like running a
Roland with Versaworks RIP and using the Max Impact preset. That preset, btw,
does not honor embedded profiles in the incoming files. In fact, for your plan
here to work, any RIP would have to be configured to honor embedded profiles.
Otherwise what you’re doing will not work.
>
> But what I did not expect was that the blackest pixels in the converted test
> image that started out as RGB 4,4,9 are now RGB 30,29,28 after conversion.
> That sounds crazy to me!
> I have not printed this converted test image yet. I don’t want to waste my
> money printing this converted file if I have got this wrong. But everything
> else looks like what I would expect.
This would indicate to me that the machine is applying some CMYK printer
profile — which would of course imply that the printer is using some sort of
color management -- with a not-very-robust black point. You might think that
would be at odds with the rest of the image being over-saturated, but it’s
really not. There are infinite ways to create a profile.
Out of curiosity, what type of media is being used here?
Mike Adams
Correct Color
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