Focus stacking a wasp nest

When my wife found this lovely little wasp nest, less than 3 cm diameter, I thought it would be a good subject to experiment on with focus stacking. It's my first try:




Above is the result of stacking just 3 frames, each separated by 1/4 inch (6.35mm), with CombineZP Focus Stack. Each frame was taken through a Sigma 105mm F2.8 DG Macro. Focus was manual, fixed, and the camera was moved with a screw-thread on a heavy pillar between each exposure. Manual exposure, always f 5.6 1/45 sec.

The result is pretty satisfactory, but there is some halo due to ambivalence in the software around the left side of the image. I actually took about 11 frames, at 1/16 inch apart. Stacking more than 3 frames, to reduce the spacing, made the halo effect worse to my surprise.

I had not forseen (silly me) that there would be a small shift in perspective as the camera+lens moved relative to the object. I wonder whether it might have been better to keep the camera fixed and shift the focus a little bit for each exposure?

Just for comparison, below is a conventional single exposure at small aperture to get good DoF. Best focus was at the centre of the nest; even at f 16 the DoF was not enough to keep the nearest and furthest points in sharp focus - but at least there are no software haloes!




Who else has experimented with CombineZP, and what have your experiences been?

Martin