Just thinking out loud why there seem to be SO many 20mm f1.7 lenses for sale? Are people more fond of their zooms? Are they disappointed in the focal length? I have a 50mm for my full-frame DSLR that doesn't get used much, but I do like it for the shallow depth of field, and speed at f1.8. Seems like the 20mm would fit the same bill. Perhaps the Pan/Leica 25 is better suited? Thoughts???