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The Darkroom Dealing With Dynamic Range
By Darryl C. Nicholas May, 2003
The Darkroom
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Photos © 2002, Darryl Nicholas, All Rights Reserved
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I love digital cameras. However,
they all have one serious problem. They tend to block up the shadow
tones. That is, they have a short dynamic density range, compared to
film. If you use very flat lighting you get simply great pictures. But,
if you shoot outdoors on a sunny day or if you use the built-in flash,
you will tend to wash out delicate highlights and block up the shadow
tones in one big black glob. It’s a shame that digital camera
manufacturers do not publish a dynamic density specification for their
cameras like the scanner manufacturers do. But, the truth is, the camera
manufacturers do not have any specification that they are proud of.
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And, if you try to scan transparencies
or negatives on low cost flat-bed scanners, you’ll have the same
problem. Many folks intentionally overexpose their color negatives to
improve shadow tone definition. The technique works great when printing
the negatives in a wet darkroom. But, when you try to scan those negatives
on low cost (short dynamic density range) scanners, then you will lose
delicate highlights and the deep shadows will go solid black. You need
a dynamic density range of 4.0 or more to handle overexposed color negatives
correctly. By the way, some scanners, such as Nikon’s 8000ED/4000ED,
do a great job on color negatives because they have that greater dynamic
range—the Nikon’s mentioned deliver a 4.2 dynamic density
range.
Solving The Problem
There is a Photoshop work around that can help with the problem. You need
two identical images; one with good shadow detail and the other one with
good highlight detail. If you’re working with a color negative on
a scanner, use the manual scanner adjustments to create those two different
scans. Then proceed as noted below.
In this example, #1 (unaltered original image) was shot with a point-and-shoot
digital camera in the $1000 price range.
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Notice that the black cat went
to a black glob and the bright daylight that is outside the window washed
out the brick wall.
If you take #1 and go into Photoshop, it is possible to lighten it and
bring up some detail in the cat (#2). But, in the process, you lose even
more of the surrounding detail as it all washes out. Also, the edges of
the cat’s fur wash out as in #2.
Here’s the fix. Make a duplicate copy of #1 in Photoshop (Image
to Duplicate). Then, use the Photoshop tools to lighten the duplicate
image until the detail in the black cat begins to become visible. Don’t
worry about the washed out edges of the cat’s fur.
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Next, do a “Select All”
on the original image (the solid black cat) and copy it to the clipboard.
Highlight the image that you lightened (#2) and paste the copy of #1 onto
#2.
You should be able to go to the Layers palette and it should look something
like #3 with the dark copy (Layer 1) on top of the light copy (Background).
Next, get the Erasure tool (#4) and a soft edged brush. Set the tool’s
opacity to about 20 percent (so you can make overlapping erasures and
therefore have smoother control to blend the erasing activity) and start
to erase “holes” in the top, black, cat. As you do, the lighter
cat below (with all the detail showing in its fur) will start to show
through. Eventually, as you perform the erasing, the cat in Layer 1 will
look like #5. And, when you look at the total picture it will look like
#6.
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Once I had lightened the fur
in the cat (#6), I flattened the image, and then I did a selection on
the red brick wall and darkened it. Then, I did a second selection (#7)
on the lace curtain in the upper right corner and lightened it. I thought
it looked a little dirty in the original picture.
If I had simply done a selection on the cat and tried to lighten it, the
fur around its face and the fur on its tail and paws would have washed
out too light as is demonstrated in #2. But, by doing the “rub through”
technique I could control how much of the super-lightened cat, from below,
would show through the top Layer. And I didn’t have to worry about
trying to make a selection around the soft fur outline of the cat, which
would have been a bit difficult to do. The cat, D-MAX, is a 2-year-old
registered Bombay that totally rules the household. And, because of his
black fur, has proved very challenging to photograph.
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If you’d like help with
calibrating your Epson printer and your PC computer, write to me care
of the magazine (editorial@
shutterbug.net). For only $3, you can get my CD-ROM that will walk
you through the process using only the tools in Photoshop (the full version)
and your Epson printer driver.
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