Hi there. I'm new to Canon dSLR's - got blessed by an MR member selling me a used one in great shape. A 20D with the 18-55 EF-S Lens. I have an Olympus system so that's what I'm used to. I bought the 20D for shooting telephoto with high ISO. I see how expensive the telephoto lenses are so will probably rent the lenses. Questions are: 1. I see the EF and EF-S, and understand that the EF series is from the full-frame/film format. The EF-S works only on certain Canon digitals. Does it also follow that EF lenses are of higher quality than EF-S? 2. I tried the EF-S IS 55-250 (the lens IS is kinda cool ) at the camera shop while getting the rental list. If EF lenses have higher quality, would it be worth renting the EF lenses, which are considerably more costly, than say, buying the EF-S lens outright? I foresee shooting with a telephoto only 2-3 times a year(at Sci-Fi conventions and the like). I'm more a landscape/architecture/cityscape and Aviation (the planes while on the ground or takeoff/approach/landing) photographer. Also seems to me that the EF lenses (white bodies) and are not as portable as the EF-S lenses. Thanks for everyones help on this forum. Sorry I'm sorta lazy to search the web's vast amount of information.