The Darkroom
Dealing With Dynamic Range

The Darkroom

Photos © 2002, Darryl Nicholas, All Rights Reserved

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 It's a shame that digital camera manufacturers do not publish a dynamic density specification for their cameras like the scanner manufacturers do.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.


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.


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.


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.


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.


If you'd like help with calibrating your Epson printer and your PC computer, write to me care of the magazine (editorial@ 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.