I thought I had gained a resonable grasp of photography, then I became interested in Macro and it feels like day 1 again
Know what you mean

! Some aspects need a
closer look. That can become a
narrow view - you'll have to decide for yourself where the boundaries lie between those!
DOF - start here, in the FAQ section:
http://www.photomacrography.net/forum/v ... php?t=7359
Diffraction - start here
http://www.cambridgeincolour.com/tutori ... graphy.htm
Your pixels are I think about 16µm² which doesn't appear in their table. You'll need to do some tests to see what happens. You may find say, that f/8 or 11 is about your limit as
effective aperture, going narrower than which, you lose more to diffraction that you gain from DOF.
Effective aperture is marked aperture x (magnification + 1). So at 1:1 your f/5.6 is effectively f/11.
For my fatter camera I use "f twentysomething" as a limit, with the simplified calculation which seems to work:
DOF = 2 x CofC x (marked f no)x (m+1)/(m²)
For CofC, see previous posts.
Then remember your focus steps have to overlap. No harm in a few too many steps. About 3/4 of DOF seems to avoid me any trouble, though others may choose 95%.
The spreadsheet is worked from the simple "thin lens" model:
( (1/image distance) + (1/object distance) = (1/focal length) )
and magnification = image distance / object distance.
Lenses aren't thin of course, but for
relative movements I think the model's good enough. (Rik??)
You can use the lens' marked "f" number whichever way round it is.
Right, off to do some plumbing. Calculator stays at home...
