We all are familiar with the concept of depth of field, which describes the range of distances over which an image is in focus. This is determined by the f-number at which the image is taken, smaller f-numbers (larger lens openings) yielding shallow depths of field, larger ones (smaller openings) yielding greater depths of field. Often we use a shallow depth of field to emphasize our subject; this is especially useful in portraiture. But sometimes we wish a large range of distances to be in focus, and this can often exceed what is possible using a large f-number, even using hyperfocal focusing. In addition, an unavoidable disadvantage of using a very high f-number is that diffraction begins to soften the image, and this cannot be removed completely in post-processing.
There are at least two methods to extend the range of in-focus subject distances that appear in an image. One is to use a tilt-shift lens, an expensive option, and one that requires some practice to use successfully. The other is to take a series of images focused over a range of distance and somehow stitch them together. This latter technique is known as focus stacking, and is the subject of this article. With any Nikon camera and lens, a tripod, computer software, and perhaps some additional reasonably inexpensive equipment, this is easy and fun to do.
Fig 1. A typical frame from the stack.
Click for an enlargement
The basics of focus stacking are straightforward. A series of images, each focused in a slightly different plane, are combined by specialized software that utilizes the sharpest parts of each image to produce a single image that is in focus over a wide range of distances from the camera.
No matter what technique you use to obtain a series of differently focused images, you will need computer software to stitch them together. In this article I discuss the use of three packages, Photoshop® (CS6), Zerene Stacker® (version 1.04), and HeliconFocus® (version 7.5.1). While this isn't a software review per se, I will touch on the strengths and weakness of these packages as I have used them. The last two programs each have more than one way to combine the images, and I will illustrate output from each.
Focus stacking can be effective in two very different contexts. The first is in taking landscapes, where the photographer wants to keep objects spanning a large range of distances in focus (this is a traditional domain of the tilt-shift lens). The second is in close-up photography, where we want to keep an entire object in focus. In this article I deal only with the latter.
To read the rest of the article, please log in. This article is available to all Silver, Gold and Platinum Nikonians members. If you are not registered yet, please do so. To discover the world of Nikonians and the advantages of being a registered member, take our short discovery tour.
More articles that might interest you