70-200 f4 IS or 70-200 2.8 IS Mk 1.
I can buy a new f4 or second hand f2.8 MK1 for about the same price. Just sold my only landscape lens so no more of those.
I would most likley us it with a 1.4 extender for photographing seabirds on a boat. With the extender does it make the f4 a f5.6? I used a 2.8 MK2 recently and it worked well but I do wonder if the expense of the 2.8 is worth it. I'm looking for a lens that I can hand hold all day. I have read a good review of the Sigma 70-200 f2.8 which is well priced.
Any comments from those that have used both of these lenses more than welcome - other options put forward also considered.