Re: Delta H Comparison
Re: Delta H Comparison
- Subject: Re: Delta H Comparison
- From: Klaus Karcher <email@hidden>
- Date: Sat, 08 Aug 2009 17:06:09 +0200
Jon Crook wrote:
Is anyone using Delta H for quality assurance?
∆H max primaries and ∆H average CMY-Grays is part of the Fogra Media
Wedge 3.0 evaluation (ISO 12647-7).
<http://digitalproof.info/colorsync-users/proofQC_example.pdf> is an
exemplary Proof Evaluation. I wrote software to shows graphs like this
immediately after each control stripe measurement. They are for internal
quality monitoring of an GMG proofing system. My software also prints
evaluation stickers, maintains a database of measurement data for every
proof and offers tools for long-term in-depth quality analysis and
troubleshooting.
IMHO ∆H is not a really descriptive measure. If there is no need for
symmetrical measures (i.e. no need for interchangeable reference- and
sample-values) there is IMHO a better alternative I suggested years ago,
see <http://digitalproof.info/perceptual-rendering/Farbtonverschiebung.pdf>:
My "Delta H replacement" is a vector in the ab-Plane. It is orthogonal
to the reference color as long |∆h| ≤ 90° and therefore points to a
meaningful direction (in contrast to ordinary delta H). For |∆h| > 90°
it becomes a general vector. My |∆C| never exceeds |C reference| and you
can add my delta H, C and L vectors to get delta E .
Klaus
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