Digital BW, The Print

Truman Prevatt wrote:

>It probably is psychological. I remember Adams talking about the optimal 
>size for a print for impact - bigger is not always better. I think it 
>has to do with viewing range - smaller prints are viewed closer and 
>because of this they will have a different impact than if the same image 
>is printed in a larger print. If you measure the difference on a sensor 
>there may not be one but if you ask someone they will tell you there is.
>  
>

Actually, it's perceptual (which makes it both psychological in the 
traditional sense and a physical perceptual effect).  This is a field of 
psychology my father helped lay out the bricks for in the 1960's.

It's like an adjacency effect of color.  In color perception, adjacent 
colors may skew our perception of those colors.  A simple example is 
that we use a neutral gray background and desktop when doing critical 
color work, knowing that the mind can be "fooled" by colors off from 
neutral.

Similarly, if you size down a a tonal range and compress it across a 2d 
space, certain tonal transitions will be harder to perceive.  Instead, 
the mind saves processing and interpolates.  Therefore, in many cases, 
perceived contrast of a smaller print of the same image will be higher 
(intermediate tones get winnowed out by the brain).   This is why 
studies of the discrete colors perceivable by the human mind/eye 
combination also generally use a published control of the distance over 
which the tonal variation occurs - different tonal changes are 
perceptible over different 2d distances at different viewer distances. 

The simple fact is that, like any processor and software, the capacity 
for the eye/mind to process data over a particular period of time is 
finite.  So, it sorts info into discrete chunks or steps for pre-processing.

In fact, it is these very underlying effects that make  the idea of 
photo-mosaics not just theoretically possible, but an interesting effect 
for illustration.

All that said, when making a larger print, you may find you want to 
increase the contrast to retain the same PERCEIVED contrast range IF you 
expect the viewing distance to be the same as it was for a smaller print 
of the same image. That's why SOMETIMES, simply reading the numbers from 
a densitometer, spectro, or in Photoshop's info window isn't enough.  
Some things about human perception remain subjective and non-formulaic.  
For those who always depend on such tools to pick a final print, this 
may be counter-intuitive, but art is inherently subjective anyway. 
Nothing ever substitutes for personal vision and real-world perception 
in the final analysis anyway.

Hope this helps.



 
Keith Krebs

"Just some guy," caretaker of the Multiverse's largest EPSON printer 
User Community (highly recommended by Vogon Poets and MegaDodo 
Publications), at:
http://groups.yahoo.com/group/EPSON_Printers/
and  the Multiverse's largest Canon printer User  Community at:
http://groups.yahoo.com/group/Canon-printers
"For the rest of you out there, the secret is to bang the rocks together 
guys"