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From: strata_ranger@xxxxxxxxxxx To: gimp-developer-list@xxxxxxxxx Date: Sun, 18 Dec 2011 10:59:32 -0800 Subject: Re: Luminosity in LAB does not agree with Wikipedia or Matlab Notice that if you perform a Midtones correction of about 2.2 on Wikipedia's CIELAB L channel then the result roughly approximates GIMP's L channel decomposition. (Conversely, apply a Midtones correction of 0.45 to GIMP's L channel and compare results). Found a faster way to demonstrate it: Create a new image with a black-to-white linear gradient running from left to right across the image (i.e. even distribution of grey tones). Decomposing the image into LAB space does not yield an even distribution of values across the L channel, but something that more closely resembles a Midtones adjustment in the 2.2 to 2.5 range. -- Stratadrake strata_ranger@xxxxxxxxxxx -------------------- |
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