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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