Two free books on macro, close-up, focus stacking, and macro-panoramas at the following link. The second book has specs on over lenses used for macro and close-up work, including focus throw specs.
http://macrostop.com/
Free e-book Primer on Macro and Close-up Photography
Moderators: rjlittlefield, ChrisR, Chris S., Pau
Free e-book Primer on Macro and Close-up Photography
MacroStop photography videos.