How a Digital Darkroom Improves
Even Correctly Exposed Photos
Most of us would be delighted if the only thing darkroom software could do is save our photography from our mistakes. But it gets better
than that. You can improve photos you think can’t be improved—at least not technically—by running them through programs such as
Photoshop and Paint Shop Pro. Maybe you have been looking at marginal photos for so long that they look perfect to you. It’s similar to
our inability to distinguish among shades of white. We don’t see that a photo’s slightly overexposed or underexposed, that there’s a green-
ish cast to it, or that it has a dullness that’s not really apparent until darkroom software banishes the flaw. Software makes good shots into
photos that pop off the screen and the paper. These improvements are based on the information the software finds in a histogram, which
is a record of the color and brightness values
of every pixel that makes up your picture.
Here’s how it works.
156 PART 3 HOW THE DIGITAL DARKROOM WORKS
To each pixel, the software assigns a
tone value, a number from 0 (represent-
ing pure black) to 255 (for white). The
software then counts how many pixels
of each tone value are contained in the
picture and can often display this infor-
mation in a bar graph called a
histogram. Along the horizontal axis
are the tonal values. Each bar displays
the number of pixels in the photo that
have that tonal value.1
When you graph all 256 tones and the
millions of pixels in an image, the his-
togram can look something like this.
There is no “right” way for a histogram
to look. It can have a single, bell-
shaped curve in the middle, or it can
have multiple humps. A photo with a lot
of snow or sand will have a big hump
on the right side, while a night scene
might have a lot on the left side.2