Re: How to profile metallic paper
Re: How to profile metallic paper
- Subject: Re: How to profile metallic paper
- From: Klaus Karcher <email@hidden>
- Date: Thu, 04 Nov 2010 18:11:35 +0100
Robert Rock wrote:
Perhaps this is a useless work-around suggestion, but here goes, and please
don't laugh at my non technical approach.
IMHO this is a quite interesting idea and there's absolutely no reason
to laugh about it.
[...] So for this case, how about taking a very
accurate digital photograph [...] After profiling the camera, why not then
photograph and print your test charts, as accurately as possible, and make a
profile from there? Again, not a sophisticated solution, but maybe closer
than no profile at all. It seems we are better able to control the light
reflections in a photograph than under the lens of an i1Pro, DTP20, or other
instrument.
Again, please don't laugh. But tell me what's wrong with my logic. I want to
learn.
To simplify matters, I wouldn't take a camera but a Cruse scanner to
capture the target: It should be quite easy to set up a scan mode where
the amount of specular reflection captured by the scanner corresponds to
the intended viewing condition (it is a purely visual decision up to
this point: you just have to adjust distance and angle of the lamps
until the gloss level of the scan meets your expectations). You don't
even need a special profile for this mode, the usual calibration tools
to compensate for exposure variations and lighting falloff should be
sufficient. What you get is a scan of your testchart with very even
illumination (in contrast to camera-based setups you get perfectly even
illumination with minimal effort). The rest of the procedure is outlined
in the ArgyllCMS documentation (see "Typical usage Scenarios and
Examples -- Reading a print test chart using a scanner or camera"
<http://argyllcms.com/doc/Scenarios.html#PP4>). Current Cruse
installations already contain a scanner profile constructed to return
absolute color values. As a Cruse scanner is no colorimeter, there might
be some sensor metamerism issues*, but I guess the result is still much
better than what can be achieved with 45°/0° measurements or targets
printed on substitute papers.
*) sensor metamerism issues can be minimized with a scanner profile
optimized for the inkset of the printer, but this additional effort is
probably dispensable.
Klaus Karcher
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