The other day my friends dad came into his kitchen with a Canon eos 700, a 35-80mm power zoom AND a Canon EF 100-200mm 4.5 A. He announced that he was going to take them to Jessops and find out how much they are worth, I think he thought he was going to get loads for them because he paid a lot 8 years ago and has hardly used them. I pointed out that Jessops don't deal in second hand goods anymore and I offered to try and find out how much they were worth by looking on eBay. I've tried the 100-200mm lens on my 20D and it works fine and I am aware that it converts to 160-320mm on my digital. I think I want it because at the moment the only other lens I have is a cheap 28-80mm 3.5-5.6 but I don't know what it's worth or how much I should offer him for it. I've looked on eBay but it doesn't seem to be a good guide. Can anyone help? I just want to know about the telephoto lens. Thanks in advance for any help.