[argyllcms] Re: A better way to measure paper white?

  • From: Ben Goren <ben@xxxxxxxxxxxxxxxx>
  • To: argyllcms@xxxxxxxxxxxxx
  • Date: Fri, 30 Oct 2009 16:36:30 -0700

On 2009 Oct 30, at 4:19 PM, Graeme Gill wrote:

Ben Goren wrote:

Graeme, might it make sense to add an option to chartread that will remember each of those start / stop white values, average them all together, and replace every white patch in the chart with that value?

For strip type instruments you're right that paper gets measured
at the end of each row. The problem is that because the paper isn't
delineated by spacers, it's difficult to know what is valid paper
and what is not.

I did think about that, especially since one could (conceivably) scan past the edge of the paper and onto the table. That's partly why I suggested it as an optional flag; give the user enough rope to hang himself with, as it were.

But if only two instruments could make use of it, and one of them is only supported in the beta release, I can see why it might not be worth the bother. Still, feel free to steal the thought, if you like.

Hmmm...thinking a bit further...the window on the scanning table for the i1 is a set width. You could perhaps modify printtarg to put alignment marks indicating ``line up the edges of the window here.'' Might even be able to squeeze in another column or two of patches that way, though the instructions would have to read ``start scanning at the very end of the window and be sure to scan all the way to the other end.''

As for paper white in camera profiles...yeah, I know all about that. That's why I've worked out a setup with four strobes at 45-degree angles surrounding something to be copied. Falloff (``vignetting'') from the lens can still be a problem, but it's minimal enough to not worry about on a decent stopped-down macro lens.



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