[argyllcms] Re: chartread feature request / pipedream...

  • From: "Alastair M. Robinson" <profiling@xxxxxxxxxxxxxxxxxxxxxxx>
  • To: argyllcms@xxxxxxxxxxxxx
  • Date: Thu, 08 Jul 2010 09:32:49 +0100

Hi :)

On 08/07/10 01:59, Graeme Gill wrote:

the approach would be to get profcheck to annotate the .ti2 file
with the delta E of each patch, and then make chartread offer to read
strips in max to min delta E order.

OK that would work - and probably be much easier to implement!

But I'm more interested in why you need to use this approach. Do
you think strips get misread ? Do the patch values vary a lot with
each attempt at reading ? Is the instrument moving too fast ?

I'm not 100% sure, but I think it's a case of the instrument not moving smoothly, juddering, and letting stray light in - if the charts are linearization charts then a plot of input vs L* tends to make the bad patches instantly visible and they're generally lighter than they should be. In other words, it's probably just that my technique sucks!

I was under the impression that it was a common problem, though - I'm sure I've seen several references either here or on OpenICC to the need for averaging multiple testchart readings (and discarding outliers rather than just finding a mean) when using an i1 - in fact I even saw reference to it on an eBay listing for a used DTP20 once!

Anyhow, when I read, say, a 1-page A4 testchart, I think the odds are fairly even that I'll have either 0, 1 or 2 bad strips on the first attempt at reading.

I've changed the algorithm for "slicing" the patches out of a strip
in the development code stapshot
- does this work any better ?

Ah thanks - I'll give that a try when I get a minute :)

All the best
Alastair M. Robinson

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