Having looked around for a focus stacking app for the MacBook I ended up installing the trial version of Zerene Stacker which gives 30 days full use before deciding whether to buy it.
My first attempt, eight focus stacked images of a flower on my Venus Flytrap:
Canon 50D, 70-200mm lens plus Raynox DCR-250 Super Macro Conversion Lens, LED ring light.
Not a startling image but I'm pleased with it as a first attempt working with jpg images.
I must admit I prefer the look of the program compared to CompineZP on Windows. You can see the final image being built up which gives a chance to see if any of the initial images might be causing problems. It was much easier to use and really flew through the align and stack process.
The Ophelia Sun
9 hours ago