Hi all, I'm looking to get the Nikkor 50mm f/1.8D AF lens for my Nikon D80 and a potential Nikon F100 (film). I'm more interested in getting it used, but when I go onto websites like ebay to find them, it seems like there are many versions of the lens. Are they all the same? How can I tell the difference? The only way I can tell it's different is just by looking at the provided photo if the lens. Are the newer 50mm lens better than the old ones (i.e. the E series)? Would all of the Nikkor 50mm lens work on both the D80 and the F100 despite the different versions of the lens? Also, what does the f/ thing mean? I was orginally lookin for the 50mm with f/1.8, but I've noticed some 50mm with f/1.4 as well. Are lower f stops better? Thanks for answering my questions! I'm just starting to get into slr photography and any advice is appreciated.