Interest in ‘focus stacking’ is increasing rapidly. In this short article, I would like to suggest why this might be. For those of you unfamiliar with focus stacking, let’s make clear what it is.
Just as exposure bracketing and HDR are popular, a technique where a number of photos are taken at different exposures and then seamlessly combined into a final photograph, so focus stacking takes several photos of an object at different focus points, and combines these photos seamlessly into a final photo that represents the object as if it had great depth of field (DOF). Focus Stacking is essentially ‘focus bracketing’ and the result is a photo where everything appears to be in focus, whether it is near or far from the observer.
The resulting photo from combining images at different focal distances can be remarkable and advances in software like Adobe’s Photoshop CS4 and programs like Helicon Focus are perfecting this technique. Here I am not going to show you how to stack photos. There are many tutorials on the Internet that do this well. What I would like to discuss here is a possible reason why focus stacking is so appealing to the eye.
Human vision can only focus on one area of a scene at a time. No matter how much we take in, no matter how much is going on around us, we can only focus at one point at any given time. Everything but that point of focus is, to some degree, out of focus. Just try it now. Look across the room at an object and note how your peripheral vision on either side of the object is slightly out of focus. We are so used to this phenomenon that we are seldom even aware of it.
Although everything around us is not in focus except where we look, this does not affect us because wherever we look, things are in focus. The mind automatically behaves as if we live in a world where everything is always in focus, because as we look here or there, things are always in focus, which brings me to my point:
The photos we take, at least at near distances, are seldom in complete focus. In fact, we have no choice but to focus on one area of a scene or another, and all other areas will be at least somewhat out of focus. This is why photographers make such a big deal out of depth of field (DOF). In particular, macro photographers struggle to get this beetle or that butterfly (in its entirety) in focus. We push our f-stops so high that diffraction often destroys our resolution before we can get everything in focus. Enter focus stacking.
Focus Stacking creates a photo image where most everything is in focus, just like our mind assumes the world out there is, as well – in focus. While with most photos we are drawn to wherever the photographer happened to focus, with a photo made with focus stacking we are free to look anywhere we want. The photographer no longer dictates where our eye should go by his point of focus, and we are at liberty to just kind of look around as we like.
This newfound freedom brings a kind of spaciousness to the mind and stacked photos have an almost 3D quality, when really the only thing new is that the whole picture (or at least the main subject) is in focus. Let’s look at an example, which you will have to scroll up and down to see in full:
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Here is a photo that has not been retouched of a little spring diorama, some Michigan ferns emerging. Notice how the ferns in the front are in focus, but those in the back are not. Our eye is drawn to the area in the front where everything is in focus. Trying to get the whole scene into focus through manipulating the DOF would be difficult, if only because the woods where these ferns are growing is quite dark.
Now let’s look at a stacked photograph that is a blending of four different photos, each focused on different areas of the scene. As you can see, at least the main subject (the various ferns) are in focus. I am sorry these shots are so small. The originals are shot with the Nikon D3x and are huge and clear as a bell.
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As you look at this photo, see how appealing it is to have things in focus and to be able to look around the scene as opposed to being denied that freedom by having some areas of the photo out of focus. I point this out because I believe that focus stacking or focus bracketing will become even more important to us than HDR or exposure bracketing have up to this point.
Camera makers may eventually even include focus bracketing as a feature where, perhaps, we focus on the front and back areas of any scene or object and the camera produces a series of bracketed photos with the focus at different layers between the two points we set. We could tell the camera how many layers or photos we want. This could be very useful, because one of the problems of focus stacking is taking the photos fast enough to capture the images before changes in lighting, etc. set in.
I have been experimenting with focus stacking (many hundreds of stacked photos) using both Adobe Photoshop CS4 and Helicon Focus. In Adobe Photoshop, you want to place the stack of photos as separate layers and then run the Auto-Align command (which lines up the photos with one another) and next the Auto-Blend command, which seamlessly blends the stack to produce a single resulting image. This process is not faultless and requires quite a learning curve for photographers, not to mention the need for continued progress by companies with perfecting the software used.
So far, the results I am getting are wonderful. The example used here gives you some idea of what a stacked photo can look like. I am working on a longer article that goes into some of the various techniques (and problems) one has to keep in mind when processing stacked photos.
Nevertheless, the results of focus stacking are very impressive and, more important, can be deeply satisfying, especially for those of us who yearn for greater depth of field (or its equivalent) in our work.
Thanks,
Michael Erlewine (MacroStop.com)
