Re: purpose of Granger rainbow chart?
Re: purpose of Granger rainbow chart?
- Subject: Re: purpose of Granger rainbow chart?
- From: Jacob Rus <email@hidden>
- Date: Mon, 8 Mar 2010 10:58:32 -0800
Marco Ugolini wrote:
> "Tonal discontinuities" such as which, exactly?
Sorry, I suppose there are no "discontinuities" in the luminous
landscape max-for-each-hue-and-luma, but neither will there be in the
same thing piped through a CMM and printed. What I meant to say is
that the function is not smooth (continuously differentiable), and in
particularly noticeably has a nasty diagonally slanted edge in
lightness (L*), where the derivative changes abruptly. This visual
artifact is clearly visible
<http://www.luminous-landscape.com/images31/Granger_Chart.jpg>. I
don't understand why it wouldn't make more sense to create test images
with lightness rather than luma on the vertical axis, especially
considering that most CMMs use CIELAB as a PCS. I suppose it would
take crunching some numbers to make such a test image, and wouldn't be
quite as easy to manage in Photoshop.
Cheers,
Jacob
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