I have this combination and an annoying problem.
I usually use single AF and centre point and find that if I try to focus on a bird in flight, that rather than latch on to the bird at a distance, the camera moves the AF to focus on a nearer point or worse hunts back and forth. What was initially almost in focus in the viewfinder is thrown out of focus and the opportunity is lost. Is there a way of making sure that the camera actually focusses toward infinity rather than to the nearest point. I use the back button to focus.
On the occasional times that I used my 100-400 (on any DSLR) for BIFs, I find that setting the focus limiter to the farther setting (6.5 m - infinity) speeds up AF. I likewise turn IS off at shutter speeds of about 1/640 sec or faster.
Mike - how big are the birds in your viewfinder? If they're really small, they may be harder to track.
Here's my 5D and 5D2 setup, roughly...
Focus: AI Servo
Center point selected
Expansion AF points turned on (these are the "invisible" AF points that surround the center point, and aid in tracking)
As Romy says, put the focus limiter switch to the farthest setting to speed up AF.
I don't know how fast the 5-series switches focus to the closer object when you are tracking, but with open skies, I've had pretty good luck tracking with the 5's.
That was a couple of years ago, but I think I did some modest cropping to make the image more appealing. The 5D and 5D2 have lots of pixels so you can do that.
Thanks for the reply.
The birds say a large hawk filled the centre of the screen at 400mm.
I framed on the bird, the bird was almost in focus and and I pressed the focus button. The lens instead of foccusing forward, focussed backwards, as if the bird was nearer.In the time it takes to again manually focus the moment has passed. The lens seems to think that the bird is at a near distance and attempts to focus on that and then gets lost. If the lens actually attempted to focus at infinity as the bird is actually closer to infinity, it would not be a problem. This happens quite a lot. It's as if a goal keeper in trying to save the ball, goes the opposite way.
I don't know if this is a fault or it is the way it is. The lens has had a new AF module fitted, but it is the camera that controls the lens.
This is a tough question, and I don't think the answer lies entirely with the camera. The fact is that the camera can AF on any target that the AF points detect and the camera has no idea that the bird is any more interesting to the photographer than some tree, a cloud in the background, or anything else that falls into the frame.
For me it took a lot of practice to get to the point where I can follow the bird well enough and smoothly enough in the viewfinder to think about composition, birds position of wings and so forth, and keeping the bird under the center AF point. It you have a background that is at all complex - as opposed to clear sky, etc - you really need to use the center point and keep it on the bird.
You'll still get a lot of OOF and missed shots. I'm convinced that this is pretty much the nature of the game. Shoot lots.
Avoid shooting at very large apertures. A smaller aperture will give you a bit more leeway on focus.
To the extent that you can, think about the background as well. I sometimes shoot from bluffs along the Pacific coast. If a bird comes in below me I know that the camera is prone to AF on the water or the horizon. Tracking under the center point is really critical. (And, again, managing to do this is no easy task - it takes a lot of practice.)
However, if a bird takes a higher trajectory it may have a less patterned background and AF is a bit more likely to be accurate.
In some cases, if you can shoot in a place where birds follow almost the same path as they come by you may be able to pre-focus and turn AF off. (This also points out that getting to know the behavior of the birds is also important.)
Also, try to never give the camera a chance to AF on a further subject or, worse, on nothing. When this happens you may well encounter the searching that you describe.
In the field, this is all a lot more subject to uncontrollable variables than it is in a forum post! :-)
I have this combination and an annoying problem.
I usually use single AF and centre point and find that if I try to focus on a bird in flight, that rather than latch on to the bird at a distance, the camera moves the AF to focus on a nearer point or worse hunts back and forth. What was initially almost in focus in the viewfinder is thrown out of focus and the opportunity is lost. Is there a way of making sure that the camera actually focusses toward infinity rather than to the nearest point. I use the back button to focus.
In most conditions the camera focus goes in the right direction, it is only in this situation that the focus confusion arises. I do have a problem with the accuracy
of the focus.. The problem as I say is that I can look through the viewfinder and see the slightly out of focus bird in the viewfinder, but when I press the back focus button, it all goes out of focus.It seems that the camera searches for the nearest focus point, 1.8m or 6m. It has to be said that it does not happen on every occassion, but often enough to be really annoying. It is possible that the set point of focus might be mid way between closest and infinity and it cannot work out which way to go (the goalkeeper)!
