Split Filtering in the Darkroom
By Maryann Pelland
You have an excellent negative - it looked great when you inspected it, and the contact print was good, too. But after three hours in the darkroom, your print doesn't sparkle. There's no snap. You know it has potential, but what can you do to create a crisp image, full of life, with brilliant tonality?
I had this problem one afternoon, about a year ago. I shot a roll of black and white film at a nearby pond. The light was good, the camera was good, I bracketed some of the exposures and came up with a shot of two gorgeous oak trees, incredible tones - as only autumn can provide. The trees were flawlessly reflected in the still water. The negative looked great, and I was excited.
After burning, dodging, dodging and burning again, and sailing five prints into the trash can, I stared at the enlarger in frustration. Each leaf had to stand out, etched the way the afternoon light had etched them in my eye when I made the shot. The background needed soft tones so the image wouldn't end up too contrasty.
I was certain the image could be produced the way it was meant to look. It wasn't that far off. I remembered a technique I had heard about quite some time ago called split filtering. After experimentation, I have a valuable tool that won't make bad images good, and isn't the solution to every problem, but can be the perfect next step when you need to add crispness without stretching the contrast too far.
Your first step is to make a test print on variable contrast paper. It's important that you select a good negative with a fairly wide tonal range. High contrast negs without many mid tones won't benefit from this technique. And, unfortunately, nothing can save a bad negative. In this step, you can choose to work without a variable contrast filter or use a number 2.5 (which, of course, equates to normal contrast). Determine the correct timing and enlarger aperture for the best possible print from your negative.
Once you've determined the exposure, you'll be relying a bit on educated estimating and careful playing. It may take a couple of tries to get the print exactly the way you envisioned it, but no one said this image making thing is an exact science.
For your first working print, after you have evaluated the test print, you will choose two filters at least two and a half steps apart. One will be a low contrast, one a high contrast. Exactly which you choose will depend upon the negative's properties and the result you need. For example, if your negative has good contrast but isn't providing crispness in the detail, you will first select a number 2 or 2.5 to preserve the contrast without graying it out. Then you'll need a 4.5 or a 5 to overlay some very pronounced deep tones and brighten up the highlights.
This technique, referred to as "split filtering", also splits the timing for the exposure. You'll use one filter for about a third of the total tested time, and the other for about two thirds. With our example image with good contrast but no sparkle, we will use the higher filter for the longest amount of time.
If your original exposure was, say, 30 seconds at F11 on the enlarger, you will use that aperture, insert the number 2 filter and the negative into the enlarger, and expose the print for 10 seconds (one third of 30 seconds). Now, with lights off, change the filter to a 4.5. DO NOT MOVE THE PAPER. Reset the timer for 20 seconds, expose the print, and develop it the way you did the test strip. There is no need to do anything extraordinary with the developing process.
To work with a negative that has the crisp darks and highlight you want, but is just shy of giving enough tonality, expose it with the high contrast filter for one third the total time, and the low contrast for two thirds. You can use lower numbered filters, too, like a number 1 and a number 3 for example.
The playing part comes as you determine the amount of time with each filter and choose the right pair of filters. If you experiment with different negatives, timing and filters, you will see striking results. I've found it helpful to note my results for future reference.
I don't use split filtering every day, but it has helped more than occasionally to perfect a troublesome image. Other photographers watch me play this game, ask for a quick lesson, and promptly included split filtering in their own photographic repertoire. Try it - isn't it rewarding to spend three or four hours in the dark room when you're getting the images you wanted?
Maryan Pelland is a writer, editor, publisher and photographer with an impressive resume that includes the Chicago Tribune, Copley Press, Sun Newspapers and more. We're thrilled to have her on board!