How to get number of focus steps for dof range?

[Marsu42]

When I added focus bracketing (see pull request) I wanted to add an "auto" setting that takes one shot behind and/or in front the current focus pane so that the start/end of the depth of field is where the original focus was. The intention to use the whole dof on the object and not unnecessaryly shoot some sharp air next to the object - it can be done with mf, focus peaking and dof preview but I'd like to automate it.

This would be *extremely* convenient for focus stacking, too - instead of manually guessing a stepsize for a given aperture ml could calculate it so that the dof-panes are exactly (or with a little overlap) behind each other with no missing parts out of focus!

Ml already reports the dof in meters - I didn't really look at the code yet, but can anyone tell me if there's a way to get a stepsize for the focus command from these dof values?

[nanomad]

Keep in mind that not all lenses report focus distance

[Marsu42]

Keep in mind that not all lenses report focus distance

I know (there's even a table in some wiki), but at least for the ones that so (like the Canon macro lenses) it would be a nice addition. Btw: These macro lenses (I've got both the 100L and non-L) report the distance only very roughly at far range, my 70-300L is much more precise.

Your suggestion with the per-lens table might be the only working way to go, maybe it isn't that much work to implement it after all.