My struggle with stacking focus has been going on for years. Lately, mostly because of the advent of the new Zeiss Otus series of apochromatic lenses, I have segued into deciding should I stack at all. What I have been doing recently is stacking photos at a wide-open (and fast) aperture and, after the stack, I also take a separate traditional single-shot photo at the highest aperture I can get away with. I compare the two results, the stacked image and the single-shot photo. The results are fascinating and somewhat disturbing.
Before I sing whatever praises I may have of focus-stacking, let me explain what I find disturbing about this comparison. For one, unfortunately the process of stacking images alters the color in the image somewhat and I find it very difficult to match that color later in post. Until I started taking (along with a stack) a single-shot photo at high apertures, I was mostly unaware of the differences between the two because I am not in the habit of developing the stacked-layers before I stack them, but only the final stacked image. In other words, I seldom see what the developed layers for a stack look like compared to the final stacked image because I never develop them.
Aside from a color-shift between the stacked and none-stacked photos in the comparison, the single-shot image also seems to have more luminance. Another effect (I may be imagining) is that the stacked shot has more trouble softening reflective-light (highlights) resulting in a bit of unwanted (and unneeded) contrast. The resulting effect is that the stacked image is a little crude or harsh compared to the traditional single-shot photo.
As for the merits of the stacked image, with it I am better able to control what is in focus and what is bokeh. That is the advantage of focus stacking. And most of all, by stacking at low apertures, I can keep the subject in sharp focus while having the background be whatever I want it to be, like a lovely bokeh. I can’t do that with a single-shot photo at high apertures because the increased depth of field also overwrites any sense of bokeh that is present, so, once again, there is no free lunch.
One compromise I could try is to take a single shot photo at high aperture and a second shot wide open and paint in the bokeh background from the second shot into the first in post. However, I don’t like the artificiality of this approach, not to mention the endless retouching it brings into play. I do enough retouching with stacked images as it is.
In summary, I feel I have pretty much explored the possibilities of shooting at low and high apertures, stacked or not-stacked. Perhaps this exercise could be more conveniently described as developing my technique. In that case, after all these years consider my technique more-or-less developed. Perhaps I am finally ready to take some photos.
Here is a stacked photo and a single shot photo taken at a high aperture. Note that the stacked one has a slightly more limited view because the stacking process, especially on a focus rail (as this one), restricts what is in frame. Notice the loss of contrast in the stacked image. It is also less bright. I know. I am probably splitting hairs here.
My takeaway so far is that I will be taking more single-shot photos going forward. However, as this separate stacked photo demonstrates, I also will continue stacking. Stackers out there, what are your thoughts and your experience with this conundrum?
Nikond D810, CRT Nikkor-O lens, Zerene Stacker
