Sigma 50-500mm f/4-6.3 EX APO DG HSM

yes it is a little large and heavy, not for everyday shooting, but it is the best bang for the buck when it comes to a 500mm lens. I use with my Olympus E330 and the biggest problem is camera shake at the long end. Picture that do work out are sharp with good contrast and color. There is no distortion or CA to speak of. I Would recommend a tripod or monopod but on a sunny day you can free hand it. If you want a good birding or wildlife/sports lens it is money well spent.

G Henton

huge range
good contrast
very sharp
low distortion
reasonably fast
great value

does weigh in a more than a camera
takes 2 plus hands to handle
draws a crowd
would be nice if it was a couple of stops faster

500mm mirror lens
tamron 210 plus 2x converter
Vivitrar 210 plus 2x converter

not required as of this time (1year)