Ok, the solution to the puzzler a few days ago: I was testing a new lens.

The lens to the left (24-70L) had been my walk around lens, and I finally needed something lighter,
so I got the 28-105 to the right. The size difference in the picture doesn't even tell the whole story,
since the 24-70 is almost 3 times as heavy as the 28-105.

Now you might ask how that previous picture was a test? Yes, I've taken a few quick test shots
to convince myself that the lens is reasonably sharp (it is), but the flower picture was more about
color, contrast, bokeh, and flare resistance. I'm quite pleased with this lens so far. It's a bit
under appreciated because on most (crop) dSLRs it has a somewhat awkward zoom range,
but on the (full frame) 5D it make for a very nice little walk around lens.