Digital BW, The Print

That being said though, Johnny I am not sure why you are driving things the
way you are.  The question better asked perhaps is what, ideally, should 50%
grey be?  Frankly it doesn't matter what gamma you profile your monitor at
if you have colorsync managing the conversion between the image file and the
monitor profile.  People tend to use 2.2 because of the abundance of PCs out
there and the fact that many users don't have colorsync enabled.  I am
puzzled as to your workflow and why you ask the question.


> From: Roy Harrington <roy@...>
> Reply-To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
> Date: Thu, 17 Mar 2005 23:59:37 -0000
> To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
> Subject: Re: [Digital BW] Correcting exposure for Gray Gamma 1.8
> 
> 
> 
> --- In DigitalBlackandWhiteThePrint@yahoogroups.com, "Johnny Eades"
> <jeades1@s...> wrote:
>> 
>> Thank you Steve and Dijon for responding. Focus on the 128 to 147
>> (mifflr gray) difference between GG2.2 and GG1.8. In the info window,
>> when I place the dropper over middle gray, what should it read for my
>> system set up in GG1.8? It always reads 128 except for one downloaded
>> from Jon Cone's Piezography website. Dijon, how would you have worded
>> my question?
>> 
>> Still your friend in Photography,
>> 
>> Johnny
> 
> Johnny,
> 
> What you are seeing is the results of profile conversions based on the
> working spaces you've selected in PS.   If you have a 21step in grayscale
> internally the 50 step is always 127 or 128 = 50-K.   The "128" however is
> hidden
> -- grayscale is always displayed in K which is  100-(internal/2.55).
> What you are looking at is the RGB values in the info pallette and they are
> the conversion of grayscale to working RGB.    So if you have the RGB
> working space set to Adobe RGB its a gamma 2.2 space.  Gray gamma 2.2
> matches so you see R=G=B=128.   But if you have gray gamma 1.8 converted
> to Adobe RGB the numbers are different i.e. R=G=B=145 is displayed but the
> gray value really is 128 or K=50 underneath.
> 
> With PS its very hard to get away from all the color management things
> happening under the hood.  If you have PS CS you can set the info palette to
> 16 bit and see the extra bits -- the values range from 0 to 32768 instead
> of 0 to 255 so you can calculate the midpoint which is 16384 = 50 step.
> (If you take an 8bit 21step and convert the numbers are a little off.)
> 
> Roy
> 
> 
>