Re: purpose of Granger rainbow chart?
Re: purpose of Granger rainbow chart?
- Subject: Re: purpose of Granger rainbow chart?
- From: Mike Eddington <email@hidden>
- Date: Mon, 08 Mar 2010 16:08:32 -0500
>Basically, what I meant to say is that we can see what look like sharp
edges in a funny diagonal pattern in that image. (I hope I'm not alone
in seeing this!)
This funny diagonal pattern is caused by the perceptual lightness
(usually expressed as something like Munsell Value or CIELAB L*) is
not smooth.>
Not sure I¹m following this, but when creating a granger rainbow, you¹re
essentially creating a gradient from one side of the spectrum to the other
in RGB (from 255,0,0 throughout the spectrum and back to 255,0,0, and
another scale from white (255,255,255) to black )0,0,0). The visual
discrepancies...diagonal ³artifacts² are entirely the result of the profiles
involved in displaying the data, not the data itself, so I do¹t agree that
there is anything inherently flawed with the chart numerically, or
otherwise. Theoretically there could exist a color space where there are
smooth transition throughout (couldn¹t there?), but we don¹t have the
ability to display them on our devices. It¹s use is of course limited, but I
have found it helpful in identifying gamut mapping issues when converting
CMYK profiles.
mike
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