Digital BW, The Print

Increasing contrast (which I find is what I'm doing most of the time) is the
thing that kills the histogram, because you are stretching a smaller range
of values into a larger range. Decreasing contrast shouldn't really cause
any problems. Here's an easy experiment that illustrates it: open a new
blank image in Photoshop and use the gradient tool to create a gradient from
pure black to pure white across the image. The histogram should be
relatively smooth. Now use the levels tool to reduce the contrast so the
gradient goes from, say, 60% gray to 40% gray. The histogram will be
squashed into the middle, but should still be as smooth as before. Now use
the levels again to reverse it back to a black to white gradient. The
histogram will have huge gaps, and there should be obvious banding in the
image.

Of course, as others have said, all this histogram worship has been a bit
overblown. It all depends on the image. Not all images will have smooth
histograms -- an image of black and white stripes for instance -- and the
only thing that really matters is how the print looks. That being said,
getting a handle on the principles at work has finally helped me understand
why I was getting posterization in some of my images, and switching to a
16bit workflow has helped me solve those problems.

-Jason

-----Original Message-----
From: Todd Flashner [mailto:tflash@...]
Sent: Tuesday, August 14, 2001 1:55 PM
To: DigitalBlackandWhiteThePrint@yahoogroups.com
Subject: Re: [Digital BW] Re: Image Histograms Destroyed

I assume when you fatigue the the shy it's is through darkening
it, and/or adding contrast. This always seems to expose defects in film and
scans for me. If you were to apply an equal move in the opposite direction
instead, i.e., lightening it how would it look? Heck, lets really test
it....