[argyllcms] Re: *** Spam *** Re: how many patches, profiling Epson printers

Hello Jan-Peter,

> Can you please explain, how you judge the grey-balance of the profiled
> printer ?
> - Do you print print a Lab- or RGB-greyscale ?
> - Do you have printed reference to match ?
> - What is the paperwhite of your profiled paper ?
> - What is the paperwhite of your reference (if you have one?)

I print a Lab to CMYK L* scale with a* and b* values equal to zero.
Regardless of the Intent, this method reveals any weaknesses in the
predicted neutral scale. I do the conversion in Photoshop. If I convert
Perceptually or RelCol, then I look for measured a* and b* values equal to
the unprinted substrate. If I convert AbsCol then the a* and b* values must
equal to zero.

I don't use a printed reference to match. I use my instrument as the
pass/fail criteria and calculate deviations in DeltaEab.

Paper white is Fuji Fpsatin : 93 0 -4 to 94 0 -5 (depending what I use to
measure it). I realize -4 to -5 in b* is rather high but I've seen worse.
 
> I´m mainly doing profiling for Epson Ultrachrome in the field of digital
> proofing. In this case, it is necessary to use a proofmedia, which has
> more or less the same paperwhite as the printed reference, to get a
> visual good greybalance.

So you proof RelCol?

> In the field of printing RGB-data, I prefer media with low amount of
> optical brightners resulting to a paperwhite near a=0 an b=0

Right. Like Tecco papers. I tested them once but I can't source them locally
:(

> If you wan´t to print RGB-data on photographic paper with medium or a
> big amount of optical brighteners, there is no other way as to tweak the
> profile manually.

Richtig.

> Sometimes the compensation of optical brightners in Profilemaker or
> PrintOpen helps.

Sometimes.

> If you have measurement Equipment with UV-cut, this also can help.

I tried with DTP41uv and 530 + UV-cut filter and still no magic.

> But 
> beware, that for proofing both source- and target-profile should be
> measured with UV-cut.

Are you sure? If the Source paper has *no* FWA then, in principle, measuring
with or without a UV-cut filter should have no effect. But the proofing
paper often will exhibit FWA.

> :-) Jan-Peter

Regards,

Roger Breton  |  Laval, Canada  |  graxx@xxxxxxxxxxxx
http://pages.infinit.net/graxx

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