The only way I can think of to get good macro on darker days is to a) use a tripod If you can't use a tripod, try using your flash, but diffused with some kleenex, or crepe paper so the shadows aren't harsh. Love the colour and the rain which looks like ice.
I agree with Katia, the DOF is good, I just wish that you had a bit darker area in the lower part of the picture, to balance with the bright red, and the illuminating rain drops. Anyway.. . let the techniques away, there are so much feelings in this photo, and this is what we are trying to reach here, to capture feelings in 2d pictures. Keep it up
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