Have you noticed? Photographers are combining images in all sorts of new ways. They use HDR (High Dynamic Range) to combine bracketed exposures, stitch wide panoramas with overlapping images, and shoot multiple images of a scene, changing the focus between each exposure to increase depth of field… this technique is called focus stacking.
Lens aperture is commonly used to control depth of field (DOF). In this article, I’m going to explore ways to monstrously increase DOF for landscape or macro photography using focus stacking. If you’ve dallied in HDR imaging you know that shooting a bracketed series of images−from light to dark−and using software to meld the series together, achieves an image with glowing detail from the darkest shadows to the brightest highlights Focus stacking works in a similar way, with each of the images focused at different points on the subject. After shooting the series, software melds together the sharp parts of each image.
The final image has DOF far greater than anything achievable in one shot. Focus stacking really shows its stuff with macro photography. As the camera moves closer to the subject, the DOF gets shallower and shallower. This challenge is ideal for focus stacking. Here are some examples in different shooting environments.
Focus Stacking with a Simple Landscape
For the landscape in Figure 1 I shot two images, one focused on the background (panel 1) and one on the foreground (panel 2). Photoshop’s Stacking feature handled this simple near/far job with aplomb. This is a simplified version of how the two images were automatically masked by Photoshop. Nik’s Silver Efex Pro added the final touches in panel 3. Many subjects will require multiple images to supply the desired DOF. Consider these factors to determine how many images you might need for a focus-stacked final photograph:
• Subject distance. The closer the subject, the narrower the DOF and the more images needed at different focus points. For landscape photography subjects are generally at least a few feet away, sometimes extending to infinity. Close-up/macro photography also requires more exposures.
• Geometric Complexity. This geeky term refers to subjects with a plethora of detail in every axis. In my example of the fly, complexity refers to the tiny hairs protruding from the fly in every direction. This sort of detail is much harder for software to deal with.