Focus stacking is a technique to overcome the inherently shallow depth of field in macro/microphotography. In a nutshell, you focus on the nearest part of the subject and take a photo. Then you move the camera forward a small step at a time, taking another photo at each position until you have reached the furthest part of the subject. You end up with a stack of a few to hundreds of images. Specialized software extracts the in-focus part of each image and assembles them into a single output image where everything, front to back, is sharp.

Performing focus stacking manually is a challenge, and many photographers have turned to automated rails. The movement of the camera is performed by a precision stepper motor and the movement as well as the shutter release are controlled digitally by a dedicated controller, an attached computer, or a smartphone. Here’s an example. You have determined that your subject—an insect, say-- is 2 cm in-depth and you estimate, based on your optics, that a...