If you want to see the perceptual luminosity value, convert the image
to LAB colorspace and disable the a/b channels. It gives a good
representation of the sorting.
On Aug 4, 2008, at 5:02 PM, Alex Drinkwater wrote:
Ah, OK.
So the averaging method of calculating luminosity is essentially
what the Desaturate command in Photoshop does, whereas converting to
Greyscale is done using a more accurate method (possibly the dot-
product method vade outlined, which I've also used to calculate
luminosity in the past).
Cheers for the explanation.
a|x
http://machinedontcare.wordpress.com
On 4 Aug 2008, at 21:53, Christopher Wright wrote:
Intriguingly, if you convert both of your examples to greyscale in
Photoshop (I used CS3) by desaturating, the averaging example
gives a more accurate gradation of grey values.
Desaturation doesn't even pretend to try and preserve luma -- http://www.inkjetart.com/tips/grayscale/
so while it appears more accurate, it's because it's not handling
brightness the way it should.
--
[ christopher wright ]
[EMAIL PROTECTED]
http://kineme.net/
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