Brendan - leaving the lens wide open will give shallower depth of field, and so should make the bird sharper than the rock in the background. It will also mean you can use a faster shutter speed. However, most still camera lenses work best at around f8 (I don't know about your specific lens) so there may be a trade-off to consider. On the other hand, you could ask the vulture to fly a little further away from the cliffs in the background . . . . .

Your Eastern Marsh Harrier has lovely plumage patterns, Bob. I have not seen this bird among your galleries. Is it on migration, like so many birds? I wonder about your shutter speeds for those BiF's, Bob? How many birds evolved/survived because they developed flight to enable them to migrate for food and habitat? Anyway you had a great day's shooting on Oct 18th, pollution or not. Unlike in Ireland, the air in HongKong must remain fairly static for days.

I'm just chattering while still trying to think of the crucial question about prime lenses for my usual locations & situations. I was thinking that Bob's images reveal that the greater benefits of Canon 400mm f5.6 L emerge when the bird is at distances of 50metres or more. But now I have to observe, unless I'm blind, that my vulture shot above was well within a 400mm focal length. The bird flew a path from 35m to 100m away from me during the 21 shot sequence, at all times well within frame. So what am I hesitating about? I only get nearer to big birds when I'm in special hides, which have yielded marvellous shots and video, but happens very rarely. Isn't that close to the point? I'm going to check back through my better images to nail down the exact focal lengths used effectively outside of hides (= 95% of my shots). That should lift some more of the wool and help me think more clearly. Thank you all for the helpful ideas.

Reading back I see that both Kin Lau and Bob Thompson are singing the praises of 400mm f/5.6 for BIF! That's significant; and my 1D MkIII has just arrived! Annie's suggestion will just have to wait for now!

Brendan, Yes the Eastern Marsh Harrier is a migrant. I was using ISO 320 and AV mode with the f staop at 5.6, the shutter automatically selected 1/8000 sec which was necessary as the bird made only one fast pass of the bird hide.

Bob

Brendan,

This is a full frame (without crop) of the Eastern Marsh Harrier for your info

Bob