In reply to stroppygob:
Hi there.
Just a quick thought that you won't get much out of a 300 for cricket I'm afraid - unless you're the umpire!
I've shot cricket for work in the past just on a 70-200mm with a 1dmk2 which with it's cropped sensor gives me about 270 or something like that and frankly, the pictures were shit because they were far too loose.
You're never gonna get anything close on the stumps/batsman with a 300. 500 and you're getting somewhere.
Depends what you're after though. Sounds like you know what you're doing re' the cricket and fielding shots can be great IF you can get them, which is bloody hard on a ~300 and would be for me at least nigh on impossible on a 500.
So maybe if you're thinking of getting the 300 2.8, get a 1.4x converter as well, which I guess will still give you f4.5 or if you're getting 70-200 2.8 x2 gives conversion to f5.6 max (this is what I shoot on now) and then at least you've got the option. Price shouldn't be dissimilar to that of a cheapish 50mm.
I need to get myself a 50mm though, so I can pretend to be Don McCullin shooting for
Life, rather than the grim reality