If you don’t want to plunk down nearly $10,000 for a Nikkor 600mm lens, consider the Sigma APO Tele Converter 2x EX DG. For a street price around $300 you can double your pleasure as well as your focal length.
Slip this baby on, say, a Sigma 100-300mm f/4 EX DG zoom and—bingo!—you’ve got a super 600mm lens for pennies.
This is certainly the solution for shooters who only occasionally cover sports or wildlife. I took the quick test shots below of a few cars in the neighborhood… hand-held at 600mm, 1/500 at f/8. I was expecting more softness but the images were quite sharp. In general, use a tripod or monopod for maximum stability.
Note the extreme compression and shallow depth of field at f/8 in the above shot.
I’ll run some real test shots here in the future. For now, I’ll simply say Sigma deserves some high fives.
You’ll find more information here.