Digital BW, The Print

Johnny

We debated a while back the whole issue of exposure and middle grey vs our
choice of workspace and the way RIPs map the image file to the print space
in a Same as Source environment.  The bottom line is that I would work up
your images in Roy Harrington's Lab Gray Space which is the Lab colour space
less the a and the b channels which we don't need.  In that space, the 50%
patch is L=50 which is 18% reflectance - the same as a Kodak grey card (RGB
= 118).  So if you want to determine exposure at the time of shutter release
and know that a certain part of the image will end up as expected then you
can use this as a reference.  When it comes to printing, if you are using a
RIP like QTR I would use Roy's Lab Gray Photo Paper or Lab Matte Paper and
perceptual rendering to map from the broad Lab Grey space to the narrower
print space.  The 50% slot may not stay the same shade of grey but at least
the overall balance will be the same (I am sure there are better
explanations of perceptual rendering out there!).  You will get much better
prints using this workflow.  PS and your computer's graphics card will
handle the conversion from the image file's Lab Gray Space to the monitor
profile (regardless of whether you choose 1.8 or 2.2 - I would and do use
2.2).  The important thing is to work up the image file in a sensible space
and have a sensible methodology for managing the compression in tonal range
to the print space.  Roy's ICC profiles with perceptual rendering do this
well.

Hope this helps

Steve


> From: Johnny Eades <jeades1@...>
> Reply-To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
> Date: Thu, 17 Mar 2005 22:17:33 -0000
> To: <DigitalBlackandWhiteThePrint@...m>
> Subject: [Digital BW] Correcting exposure for Gray Gamma 1.8
> 
> 
> 
> 
> 
> Let me repost the question again. Maybe this time someone will answer
> it without getting into a random discussion about 1.8 and 2.2 gamma
> rather than answering what I'm asking.
> 
> Your friend in Photography,
> 
> Johnny
> 
> --- In DigitalBlackandWhiteThePrint@yahoogroups.com, "Johnny Eades"
> <jeades1@s...> wrote:
>> 
>> My monitor is calibrated for Gray Gamma 1.8, so I should be making
> my 
>> exposures so that middle gray should read on the monitor as RGB
> 145. 
>> Is that correct? Practically all the 21 step grayscale strips are
> set 
>> up for Gray Gamma 2.2 and have 128 as middle gray. In addition to
> the 
>> monitor set up as GG 1.8 it is set so the color temperature is
> 5000K 
>> and I view all my prints under a 5000K temperature light. I don't
>> think I am the only one who is doing this, yet Ive seen no
> questions 
>> regarding this exposure question. The only reason I ask it now,is
>> that I usually need to lighten most of my images before really
>> working on them and sometimes the deepest darkest that I would like
>> to have some detail in it doesn't have any; as the result of what I
>> think may need exposre correction at time of exposure.
>> 
>> Your friend in Photography,
>> 
>> Johnny
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