Originally posted by jpzk As I always look for a suitable long tele lens, I immediately saw that the 400/2.8 would be an interesting option.
Now I wonder if a 400/2.8 would be as big/heavy as a 500/4.5 (available for Pentax) ...
What would be the corresponding F-value if one was to attach a 1.4X TC on that ?
I suppose if this ever becomes available for Pentax, considering cost as opposed to a 500/4.5, it would be something to look into.
Thanks for the "news".
JP
Using the basic N=F/D calculation,
500/4.5 would be 111mm front element diameter.
400/2.8 would be 142mm front element diameter.
I think it'll be quite a bit heavier than the 500 F4.5.