At true 1:1 macro and beyond with ordinary lenses it becomes a battle to achieve any depth of field in an image
I took a number of images over a range of apertures and with the subject at such a severe angle I found myself up at f/40.0 just to get those extra millimeters.
The combination of natural indoor lighting, a low ISO for good noise performance and an f/40.0 resulted in a long 30-second exposure - not something that would allow you to capture anything moving but just fine for my trusty old vernier that always makes millimeters matter!
Photo: Robert Rath, '366 Days of 2012, Day 74 - Every Millimeter Matters'. 30 sec at 200mm f/40, ISO 200