Re: ISO 12647-7
Re: ISO 12647-7
- Subject: Re: ISO 12647-7
- From: "Fleisher, Ken" <email@hidden>
- Date: Mon, 21 May 2007 11:20:39 -0400
- Thread-topic: ISO 12647-7
Delta H is a specific calculation:
H = Tan^-1 (b/a)
(That's inverse tangent). So delta H is a simple difference.
Delta H = H(2) - H(1)
Ken
On 5/21/07 11:02 AM, "Lee Badham" <email@hidden> wrote:
> Hi list
>
> I'm hoping someone one this list can clarify something from the new
> ISO 12647-2 proofing standard.
>
> There are now hue tests for the grey balance on a proof. This is a
> good thing in my opinion.
>
> The standard lists the tolerances as average H <=1.5, but doesn't
> list how H is calculated. I'm assuming it is done using only the a
> and b co-ordinates of the lab value of the cmy, and black patches.
> It's just that using H is confusing to me as H represents the hue
> angle of a colour. As we are dealing with grey colours, the hue angle
> itself can vary wildly, for a very small Eab.
>
> Thanks
>
> Lee Badham
> Bodoni Systems Ltd
> www.bodoni.co.uk
>
>
>
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--
Ken Fleisher
Photographer
Imaging & Visual Services
National Gallery of Art
Washington, D.C.
Phone: (202) 712-7471
email@hidden
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