I FIRST began writing this post a few months back. Timing is everything. At the time I saw what I believed to be an inordinate amount of "focus stacking" commentary. It seemed like every other image I saw posted on the various sites I frequently visit would have a comment in the caption about focus stacking (e.g., "12 shot, in-camera focus stack," or similar). On an awful lot of them, my immediate question was: "why?" It appeared to me that they were altogether too often rather normal (what I would call) "landscape" images (nature, citiscape, buildings, etc.).
Almost as if it was a hot fad that didn't last very long
THESE DAYS I don't see it (at least not commented on) nearly so often. Almost as if it was a hot fad that didn't last very long. Of course it isn't a fad at all, and properly used can be a very useful tool to achieve desired depth of field throughout an image. The concept of "stacking" images is ages old, even dating back to the days of film. Stacking can serve a myriad of purposes, and for me, since Photoshop introduced "layers" (really just a stacking concept) it has been an absolute delight to use. Not just for focus, but for other things we would like to adjust in an image (e.g., exposure).
MY FIRST exposure (see what I did there 😃) to depth of field image stacking came some years ago back in the early 2000's when third-party software and eventually mainline software (I use Photoshop) added the feature to their softwares. It was, of course, automation and it was certainly possible to "focus stack" manually, but the results were often not very good and the amount of work necessary was burdensome. I first used a stand-along software (now a plug-in) called Helicon Focus. It allowed for a series of "identical" shots (from a fixed position and a very still subject) to be loaded into it and it did the focus stacking by choosing the parts of each image that was in sharpest focus and blending them together to make one image that was presumably sharp from front to back. I didn't use it very much. Still don't. I get into why not below.
The concept of "stacking" images is ages old, even dating back to the days of film
TODAY, AUTOMATED focus stacking capability has been built into a few higher end camera bodies. An even smaller subset of those allow the processing to be done in-camera, with a focus-stacked result right out of the camera (although one should keep in mind that this processing ultimately renders a jpg image). If you are going to be doing a lot of focus stacking, I suppose this might be a pretty handy feature. For those who applaud the technology, it is - so far - only found in a handful of high-end cameras. There are a few others that will create the stack for you by making a series of exposures, focusing at intervals, but do not do the "work" of blending and combining them (which must be done in post-processing, using a software that is capable of that). Personally, at least until it can all be done as in-camera raw and raw output, I prefer it that way. And it may that I will still prefer it that way even if the raw working capability is someday found in-camera. I am a bit of a control-freak when it comes to my processing (in and out of the camera) and like the amount of control I have over the end results by doing my stacking in post.
SHARPNESS, OF course, is directly related to a lens-based concept known as depth of field. Without getting into the weeds, suffice it to say that a shallow depth of field means less of the image will be in "sharp" focus from front to back. Depth of field is largely a function of focal length and aperture on camera lenses. Generally, the smaller the aperture and the shorter the focal length, the greater the depth of field. Another variable is the distance from the lens to the subject (or the part of the subject you wish to be in sharp focus). Given those things, for years, most of us have worked with these time-tested principles to set up our shots in a manner that will give us maximum front to back sharpness - when that is what we want (it is often a goal to actually have parts of an image out of focus). In my judgment, for my own work (when I do it correctly), I have found that to yield very acceptably sharp results without any need for focus stacking. I don't engage in the proverbial "pixel - peeping," as I know 99.99% of viewers of my work don't either.
it is quite possible to actually introduce inacuracies into the process
SO. DOES focus stacking really assist in the depth of field endeavor? The answer to this depends on a number of variables, both objective and subjective. As we said, focus stacking consists of making a series of "identical" images, using different focus points from front to back, and then combining, registering, and blending them. Because this cannot be done instantaneously, it is quite possible to actually introduce inacuracies into the process. The subject (or camera) may move during or between frames, making it impossible to register two or more of the images precisely. Ironically, rather than enhancing sharpness this may well have the opposite effect of rendering the image to appear out of focus. Light conditions may change between frames. This can create visual issues which can make the image appear less sharp and well defined. Some commentators have also observed that, in their judgment, a focus-stacked image can look artificial (too sharp throughout). It is also possible that if the intervals (focus distances) between frames are too wide, the process can just simply fail to improve the image.
TO MY way of thinking, this limits the utility of this "device" to a few applications. True "macro" photography, including (and perhaps especially) product photography is the one area where I see some real gains in image quality. In close-focusing macro images, it can be impossible to have an entire subject be in sharp focus with a single image. Focus bracketing in these cases can be a real hero. But like any "tool" at our disposal, I like to follow the old adage of using the proper tool for the job. And, in my mind, a corollary to that adage is that you should not use any add-ons to the basic lens unless there is a good reason. If it doesn't truly address a specific concern or issue, and could possibly introduce negatives, don't use it. This is the same approach I take to filters, for example, on the front of the lens.
GIVEN THESE observations, I am skeptical of the benefits of focus stacking except for some very specific uses and circumstances. Most of the time I can make a nature or building shot very acceptably sharp from front to back using traditional depth of field principles. And at the same time, I wonder if using the focus stacking features in the cameras is worth the trouble. I have played with it for landscape shots, even with something relatively close in the foreground, and comparing the results with my "standard" technique, have not really been able to see an appreciable difference. It seems to me that image management is a pretty significant part of the process, both in camera or out. I briefly tried the function in my Sony A7cr to save "stacked" images into a new folder. Sounds simple. Not. Instead of creating a new folder only for the stacked images, it then creates another brand new folder when you resume shooting. And so on. It was an organizational nightmare when I ingested the files into my archive system. Not doing that one again, with several folders on the card without any way to easily recognize what was where.😓For Sony users, the newer system does have one pretty cool feature. I allows you to insert a frame in front and back of your "stacked" (or e.g., panoramic shots so you can identify where the begin and end. I always though the shot of my finger pointing was kind of awkward.
I USE Adobe Bridge as a viewer and organizational tool, and I do like the feature that allows you to mark files and save them into a stack. But I do that pretty infrequently. In my view, I will pretty much ignore the approach and process of focus stacking for 99% of my shooting. I personally think it has been lately overused (to little avail) and often misunderstood. If I was shooting lots of macro images, it would certainly be a tool I would embrace. There may be the ocassional landscape image that calls out for its use. I haven't found it yet.
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