I'm pretty new to what I call hardcore macro. When I try to go really close-up with this lens like 1:1 or lower at .19 - .4, I find the D.O.F impossibly shallow to work with. There's like a sliver of an area that is in focus. Stopping down doesn't seem to help either. Does anyone have any tips on working with a shallow D.O.F. when shooting with this lens and with Macro photography in general? Thanks!