The main question being: Is it better to use a macro rail or is it better to vary the focus of the lens?
Photography Stacking PDF Presentations:
With complex scenes, it is a good idea, not to change the position of the camera!
the use of the focusing rail leads to changes in the perspective in a way, that no stitching program can solve
But. For small subjects like this, it doesn’t matter much how you step focus, as long as:
1) you step along the direction that the lens is pointing, and
2) everything you care about ends up in the final image.
http://zerenesystems.com/cms/stacker/docs/troubleshooting/ringversusrail
Ring controlled stacking: https://www.heliconsoft.com/heliconsoft-products/helicon-fb-tube/
www.dpreview.com/articles/5717972844/focus-stacking-in-macro-photography/2
petapixel.com/2014/07/19/focus-stacking-walkthroughs-will-help-take-macro-photography-next-level/
Using the Canon Utility for software controlled stacking:
http://zerenesystems.com/cms/stacker/docs/tutorials/usingcanoneosutility
