Sometimes a Massive Lens is Just a Massive Lens
Whoa. Nikon has announced a massive new 800mm f/5.6 telephoto. The previous big boy in their lineup is the now small-seeming 600mm f/4.
f/5.6 might not seem fast enough for a lens that can practically reach out and touch the moon, but there are three things to keep in mind.
First, a modern DSLR like the D4 or D800 can shoot perfectly sharp shots at ISO 1,600 or higher. Wildlife photographers -- the obvious market for Nikon's new gotta-have-it -- aren't still stuck shooting Ektachrome at 64. Second, I'm assuming the beast will have Nikon's respected Vibration Reduction system. Nikon claims VRII can make up four stops, and I believe them.
Finally, f/stop is the ratio between the diameter of the aperture in the lens and the focal length of the lens (800mm, in this case). Can you imagine how much glass would be required to make an opening big enough for f/4 at 800mm? You'd have to mount the thing on an armored personal carrier.
No word on price, but its 600mm "baby" brother is going for $9,800 new on Amazon. So I suspect the new lens will cost... more.