Digital BW, The Print

> Dan knows his bits.
> 
> Thanks Martin, Tim and Dan.
> 
> Todd

Never lose a bit if you can help it. :-)    No magic here,  my multichannel
method avoids losing bits simply by going around the gamma change from 1.8
grayscale space to 2.2 RGB space (or vice versa).  It changes the image
appearance by avoiding changing the image numbers.  It is the same as doing
a grayscale  "Assign Profile" to the grayscale file then doing a "Convert to
Profile" to the same gamma RGB space.  In other words if you have a 1.8
gamma grayscale space and *assign* it a 2.2 gamma then convert to Adobe RGB
there will be no gamma change and therefore no histogram change.  The image
will change on screen but not the histogram.

This whole discussion just illustrates why you should not do any gamma
conversion until it is time to send the image to the printer (when it may be
necessary to make the image print correctly).  Open your grayscale scan with
no gamma conversion, assign your working gamma to it (if it isn't already
assigned by default), edit it with a curve as necessary to make it look
right, send it to the printer with the gamma tweak necessary to make it
print right.   If you use an intermediate RGB step and Adobe RGB is your
chosen RGB space then your working gamma is 2.2 and your grayscale gamma
should be that also.  If you typically use Colormatch RGB your working gamma
is 1.8 and  your grayscale gamma should match that.  Only time you get into
trouble (and need that workaround of mine) is when you are stuck with a file
in the wrong gamma space and just don't want to stay there (which was my
situation). I was converting a standard color file in ColorMatch RGB into a
standard B&W file in Adobe RGB and had to pass though grayscale mode in the
process.   Not *too* often you would have to do that, even with the odd
things folks do here on this list!   Bloom where you are planted, never
leave the gamma space your file was born in.  :-)

-- Dan Culbertson
so many years, so little time...