To Stack or not to Stack?

by Bruce Taubert

A few years ago I became quite excited about photographing “jumping spiders.” They have beautiful eyes, a hairdo that would make Alfalfa jealous, and all sorts of interesting features on their legs and fangs. The problem is they are very small—a large one is one half an inch long and most are in the one quarter inch long range. In addition they can be quite jittery and it takes hours, not minutes, to take an acceptable image. Needless to say because I am a wildlife photographer I can be quite tenacious (it took me 13 years to take my favorite flying elf owl image) and I managed to convince a jumping spider to sit still long enough to have its portrait taken. Unfortunately, when I looked at the image on the computer I was disappointed.  The eyes and hairdo were in focus but the front legs were woefully out of focus, detracting from the overall quality of the entire image.

The problem I ran into is one that is common to all macro photographers—limited depth of field at high magnifications. Even at f/16 I could not obtain sufficient depth of field to have the front legs and the eyes in focus in the same shot. I could have tried the same image at a higher aperture but the results would have been just as poor, with the addition of loss of image quality resulting from diffraction (bending of light as it passes through a small opening). Image stacking to the rescue!

Image stacking is a process where the photographer takes several images of the same subject at different focus points and combines them in a “focus stacking” software.  With the jumping spider I took five images—one of the feet on the front legs, one of the eyes, and three at different focus points in-between the eyes and feet.  I then combined them in Zerene Stacker (I also use Helicon focus) and, Voila, I had an image of a jumping spider with all of the important elements in sharp focus. The process is simple but the practice takes, well practice. Determining the number of images to take for a particular subject can be challenging and making sure that there is very little or no camera movement during the multiple captures can be just as frustrating. But, the results are impossible to get using any other method.