Focus Stacking - How Much Is Enough?

I'm seeing a lot of beautiful images in the Flora Gallery that are done with focus stacking - something I've never tried myself. I see people doing stacks of 10, 20, 30 or more slices.

How many slices does it take?
Is there really an advantage to, say, 50 slices?
Logically, there must be a point of diminishing returns. A point where all you're getting is more processing time without any noticeable difference in the image. Where is that point?

Please understand I'm not criticizing anyone or any technique, I'm just curious about focus stacking. I'm interested in people's thoughts and opinions, especially people who are doing focus stacking.

Mark, I get fine results sometimes with just a few shots in my stack....often just 5 or 6. It really depends on how deep the area you want in focus. If your are doing focus stacking in the field, movement is a far bigger issue. Even tiny movements will create some artifacts and the more slices, the greater the chance for movement. Again, I'm often pretty happy with fewer rather than more, but many of mine are in the field and using 10-15 shots for the stack.

Helicon Focus also comes with a program, Helicon Remote, that will automate your focus stack by connecting your camera to a laptop. I've used it in the lab with spectacular results, but it takes very shallow focus slices so creates very many shots....about 30-40. I can't see this working very well in the field however.

Reed

Mark, When I'm focus stacking I have a couple of main criteria. First is that I want as much dof as I can get away with while keeping the background well oof. This is important because when you have overlapping areas of sharpness, there is a law of optics that creates artifacts around the front most of the overlapped objects. The only way to avoid these are to get both (or all) of the overlapping objects sharp in a single frame. Second, as Reed points out is that movement, brightness changes, or even the slight variability in actual shutter speed that is part of all cameras, also add artifacts, so the fewer images in the stack the fewer artifacts that have to be cleaned up in post processing. In terms of diminishing returns, it depends on what you're looking for. I have stacks where I think extreme dof is an important part of the image where I've spent 3 - 4 hours cleaning up all of the artifacts.

Mark, I agree with what has already been said. The main deal for me when stacking is keeping the mood of the photo intact. Especially in flower photography, the quality of the out of focus areas is as important as the in-focus areas, so it is a balancing act. That being said, I typically only need a few images to get my main area in focus and that also means less work in post, so it is a win-win. You can download trial versions of the programs and it is a lot of fun! Before you download the trial, take a few stacked images to try them out...that way you can spend your time working with the software, not shooting something to use with the software. I'd try both Helicon and Zerene Stacker.