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: "Miles, Peter via colorsync-users" <email@hidden>
- Date: Thu, 15 Jul 2021 13:22:51 +0000
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- Thread-topic: Workflow for ‘remote’ profiling a non-colormanaged printer as a ‘back-box’
Hi Scott
Thank you for your thoughts. They have been very helpful in clarifying my
thinking.
My responses are below.
From: Scott Martin <email@hidden<mailto:email@hidden>>
Subject: Re: Workflow for ‘remote’ profiling a non-colormanaged printer as a
‘back-box’
<snip>
What type of printer are we talking about here?
<end snip>
Our staff member is not sure other than it’s a vinyl ‘banner’ printer. I am
guessing some kind of grand format inkjet.
He says the media for this printer is about 3 meters wide, or there abouts.
The vinyl prints are going to be 3.5 x 4 meters. I have asked him to get more
details.
<snip>
Are you completely sure it’s not color managed?
<end snip>
I think it is colour manged, but not as well as we would like. Judging by the
test print. (looking in our GTI viewing booth).
The staff member was originally asked to provide files as “cmyk pdf’s”. I asked
him to find out what color space they want the cmyk in. He later told me the
shop was surprised by that question and had suggested “US SWOP coated V2 should
be ok”. Some of the image colours we are trying to hit are outside that gamut.
I asked him to see if the shop would accept PDFs in AdobeRGB 1998. (The files
are natively AdobeRGB1998.) They told him that they were ‘very happy’ with
AdobeRGB 1998 pdfs. So that’s what I prepared.
<snip>
Is there a RIP involved?
<end snip>
Yes.
<snip>
Are you sure this is an RGB profiled process?
<end snip>
I would be very surprised if the printer was being handled as an RGB device by
the RIP.
I choose to profile their RGB pipeline rather than their CMYK pipeline because
I suspected that an RGB pipeline ‘happy’ with AdobeRGB1998 to be more likely to
hit our saturated image colors than a CMYK pipeline expecting US SWOP coated V2.
Conceptually, for profiling purposes, I am treating the RGB pipeline as if it
were a black-box, with a ‘front end’ that takes untagged RGB content, Assigns
it AdobeRGB1998, turns it into a PDF and then processes and prints it. Except
that the ‘font end’ steps above I’m actually doing myself.
I am doing those extra steps because I am hoping to get a wider gamut response
from their printer by presenting it with AdobeRGB1998 tagged files.
( That’s why I sent the profiling patches as AdobeRGB1998 tagged pdf’s.)
<snip>
The fact that your AdobeRGB files look over saturated could suggest that it is
color managed and is assuming sRGB for these files.
<end snip>
Thanks Scott. I didn’t think of that! I will have a look tomorrow when I’m
back at work.
<snip>
Either way, I’d send the profiling targets untagged and simply convert images
to you custom profile and again send as untagged.
<end snip>
Thanks Scott, sending untagged RGB would have been a lot simpler.
But I feel reassured that essentially my work flow is sound.
And the black point would lift? On reflection, wouldn’t that suggest that the
print process is either clipping or compressing near-blacks in image? Or both?
regards
Peter Miles
On Jul 14, 2021, at 8:45 PM, Miles, Peter via colorsync-users
<email@hidden<mailto:email@hidden>> wrote:
Hi color sync users.
This is a question about my workflow for ‘remote’ profiling a non-colormanaged
printer as a ‘back-box’.
And if you can see any obvious mistakes in my workflow / thinking.
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.
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.
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.
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.
Anyone else familiar with profiling printers as a 'Black-box'?, is this kind of
thing with the high black point normal?
Thanks
Peter Miles
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