Taken with the 70-300 macro mounted, with the 50mm reversed on the end. This setup gives an approximate magnification of 7:1. The FOV is around 3mmx2mm. The DOF is <1mm.
The ice cube had just begun to melt. It's uncropped, so the largest of the bubbles is somewhere around 0.12mm in diameter.
The primary critique I anticipate is that some people might not like the soft edges. Unfortunately, there's nothing I know how to do that would fix that. I didn't think it was enough of a problem to keep me from submitting; I still think it's all right. People may also not be fond of the vignetting.
Topically, I think it's appropriate; the title links straightforwardly to the photo itself, and a challenge like this one is essentially a free study. (I think.) I didn't shoot this for the challenge, but after thinking about it a bit, decided it was reasonably relevant (or possible to make it so with a title).
I'm not even going to try to guess my score, but my general rule of thumb these days is that I don't submit unless I think it's capable of 6+.
--
Thanks for the votes and the comments! I see that I got a vote of 1--that must mean I'm doing something right.
Statistics
Place: 29 out of 107 Avg (all users): 5.9727 Avg (commenters): 6.0000 Avg (participants): 6.0217 Avg (non-participants): 5.9375 Views since voting: 1288 Views during voting: 244 Votes: 110 Comments: 5 Favorites: 0