Quote Originally Posted by Julie Brown View Post
Thanks Dave for that information. The 7D has faster AF than the 40D doesn't it? The Crested Butte workshop was great. I will be posting those images on my photoblog in a week or so. Maybe we can meet up next trip.

Arash, that info does help! From what I have read here on BPN, the 400mm f5.6L is supposed to be excellent for BIF. I am using the 40D for the crop factor and faster fps, but often have trouble getting a bird in focus. My only opportunities so far have been with small birds, so I thought that was the problem. So what I should do is put a longer lens on the 5D MKII for the best performance? I have access to rental lenses (300 f2.8L IS; 400 f2.8L IS; 500 f4L IS).
Hi Julie,
More often that not, crop factor is not understood correctly on the internet forums, it actually has nothing to do with magnification or reach, it just means that sensor is smaller so your field of view is cropped. It is the pixel size that determines resolution or reach and in this case the difference in pixel pitch between 40D and 5DII is ~10% which is insignificant in field conditions, the sharper and cleaner files of the 5D2 puts at a clear advantage at all times.

Small birds are tougher to get in flight, I suggest that you try with larger and slower birds like Great Egrets, GBH, Hawks etc. at first and then move on to song birds in flight. The best flight lens is 500 f/4 (IMO), but you may want to practice a bit first to be able to hand hold it and track in a steady fashion.

Good luck

Best :)