Focusing (1 Viewer)

What's the trick to keeping fast moving, small birds in focus, especially when they are moving in and out of shadows at a distance?
I can't believe how many out of focus shots I take.

You do not say which Camera and lens you have but for or a start you need to make sure you are in AI servo mode (or the Nikon equivalent). Depending on your Camera you can use single AF point expansion for flyers with busy backgrounds or for birds in the sky with a clean background something like Zone AF is great as it gives you 9 AF points to keep the bird in focus. adjusting the AI servo tracking sensitivity also helps, I use a slow one for single point expansion but a fast one when using Zone AF.
As for the AF issue in shadows when the light is poor a 'fast' lens will help the AF - an f5.6 lens is slow where as a f2.8 lens is fast (f2.8 lets in 4 x more light than f5.6 so AF is better). You also need a fast shutter speed to 'freeze' the bird when in flight - the actual speed you need will depend on the focal length of the lens and the speed of the bird - with my 400mm lens I use anything between 1/1600 sec to 1/5000 sec.

It's a Nikon D3100 with a 70-300 5.6 AF-S zoom lens.

Hughv said:

It's a Nikon D3100 with a 70-300 5.6 AF-S zoom lens.

Click to expand...

I am afraid I cannot help you with Nikon as I have Canon gear. I am sure a Nikon shooter will help with the best settings!

Hughv said:

What's the trick to keeping fast moving, small birds in focus, especially when they are moving in and out of shadows at a distance?
I can't believe how many out of focus shots I take.

Click to expand...

This is the kind of situation when all autofocus systems hit sooner or later a brickwall. Subject is small and may not cover AF point and not much contrast between subject and background makes it hard to decide what is the subject it has to focus on. Little light and little contrast within the subject makes it hard for the camera to "decide" when it is in focus. Movement that causes subject to leave AF point area for brief moments (caused by subject or shaky hands) will cause AF to look for new "subject" to focus on.

Even if higher end bodies have better (faster) AF systems they still have to "see" and "know" what the subject is with one of the sensor spots sufficiently well to focus.

What helps a fair bit on the technical side -no matter what body- is to use fast lenses (i.e. f2.8 rather than f5.6), as these will get more light to the AF sensors thus giving them a better chance for them to "see" what happens, even if the lens eventually stops down to take the shot. Also lenses with HSM, USM or whatever the fast motors are called will aquire focus much faster and more reliably than those driven by the motor in the camera body or with "slow" motors in the lens.

For the time the image is taken the AF in dSLRs is "blind" and if the subject moved off the AF spot during that moment -very likely with small critters on the move- it will start looking for something to focus on as soon as the mirror is down again. Most likely it will find something in the background. This is where future development of the mirrorless cameras may give us a better tool in our hands.

With good panning technique during the shoot there is a chance to keep the subject on the focus spot and to maintain focus -if you had it in focus in the first place- for subsequent frames. Obviously you want to set the camera on dynamic AF (C-mode on Nikon) that focus will follow subject movement, and you could try using multiple AF spots that work together if your camera offers that option. However, I find myself using a single AF spot (the center one) 95% of the time and try to keep the subject centered by panning while shooting.
I also "pump" the shutter, i.e. don't push it down and fire with whatever frame rate the camera permits until the bird is gone. I shoot bursts of 3 or 4 frames and then allow AF to catch the target again before firing the next burst. As mentioned above the AF only works when the mirror is down, and only will adjust focus when it stays down long enough to do so.

Still a hit and miss game .....


Ulli

Thank you, seaspirit.
You sent me back to the manual, which I had read but didn't really comprehend.
I've now got it set for AF-C and single point focus and I expect I'll get better results.
I very much appreciate the time and effort you put into your post.