If you are working in the field and are the only one carrying your gear, I
recommend getting the 500 mm f/4 over the 600 mm f/4 as it's almost half the
weight. That makes a big difference in your ability and inclination to take
your equipment far from the car. I also suggest you looking at a good new or
used AIS 500 mm f/4 P lens instead of the AF-I or AF-S lenses. It is smaller,
lighter and much cheaper than the AF models. Unless you are doing a lot of
sports, AF is almost useless. I know that the newer lenses may be just a bit
sharper but the AIS is amazingly sharp, mine certainly is.
Jonathan Castner
Photojournalist
Denver
