>> Use the full image from 600/f4 instead of a crop of an image from a 500/f4 and the result will have less noise for a given print size. Have I got your point now?
You got it
>> I have recently been trying to explain to a friend, why buying a fast, f2.8 telephoto lens and shooting at f8, will not give him faster shutter speeds than a slower lens shot at f8.
I feel your pain
As an aside, whenever I stop down my 500/4 I think about what a terrible waste of glass and why am I hauling all that excess glass around, even if I only stop down for one shot
Does make focusing easier, though
You just caught me at a bad moment while two others are trying to justify DX via endless thread drift, rather than via the physics. Thread drifting won't solve those problems- only a bigger lens will solve those problems .
Have a nice weekend. A pint may not be enough. After this thread, how about a quart?