I made my first attempt at slipe duping a while ago, using a Nikon bellows with slide copier and a 50mm f/1.8D. I was duping onto color film and unfortunately the results were unusable (I'm going to try pre-flashing next time). Regarding sharpness, the results varied wildly from one shot to the next; I think the weakest link was my focusing technique, and possibly tripod vibration. The 1.8 did a surprisingly good job when I nailed the focus; good enough for 11"x14" prints or smaller, anyway. I do have an El Nikkor and I'd love to hear from anyone who's used that for duping (or macro).