Boost Your AF Performance

How to set up your camera and lens to get quick response when you’re shooting fast-moving subjects like wildlife
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Birds flying directly toward the camera are easier to deal with than birds flying erratically across the frame. Keep the AF point on the bird’s head (very difficult, but gets easier with lots of practice). Don’t worry about the composition; you can crop as desired when you process the image. Concentrate on the moment and keeping the AF point on the bird’s head.
Nikon D300, AF-S NIKKOR 300mm ƒ/4D IF-ED, 1/4000 sec. at ƒ/4, ISO 800

Today’s DSLRs are amazingly quick in their AF performance and firing rates, but you can make them even quicker by setting them appropriately. My favorite subjects are birds, and they present a serious action challenge with their quick and erratic movements. I appreciate all the help I can get from my camera. I discovered birds after more than 25 years in photography, and I did my early avian photography with a manual-focus Nikon F3 35mm SLR coupled with an 80-200mm zoom. As the AF film SLR and then the DSLR arrived on the scene and matured, I looked for ways to squeeze every bit of performance out of my cameras and lenses for action shooting. Here are some things I’ve learned from the more than 70 DSLRs I’ve been able to test and use in the field (a fringe benefit of working for photo magazines is getting to try lots of gear). Birds are my favorite subjects, but the techniques I’ve learned should help with all wildlife and even sports-action photography.

Use Release-Priority AF
1 Set your DSLR for release-priority AF rather than focus-priority AF (assuming it permits you to do so). Focus-priority AF locks the shutter release until the camera thinks the image is in focus. It was developed for point-and-shoot cameras to keep snapshooters from accidentally taking out-of-focus images—it’s fine for that, but it’s not for serious photography. When I push the shutter button to take a shot with a DSLR, it’s because I want to record what I see in the viewfinder at that instant, and the only correct response for the camera is to record it. I don’t want the camera telling me “You can’t have this moment because my circuits haven’t decided yet whether it’s in focus.”

Of course, in release-priority AF, the shutter will fire whenever you fully depress the shutter button—whether or not the image is in focus. So make sure the image in the viewfinder looks sharp before you fully depress the shutter button. If your DSLR doesn’t provide release-priority AF, you can still get good action shots, but focus-priority will cost you lots of shots, where the camera just won’t fire.

Use The Center AF Point
2 Use the center AF point only. This is the most sensitive and accurate point, and demands less of the camera’s processor than using all the AF points. If you activate additional AF points, it will slow things down a bit. Today’s AF systems are amazingly quick, but when speed is of the essence, use only the center AF point.

But be sure to keep that point on the subject or the desired portion of the subject like an animal’s eyes. That takes lots of practice, but do it. Put in the time, and you’ll see the results! Don’t worry about composition; most flight shots have plenty of space around the bird, so you can crop as you wish when you edit the image. Get the moment, with the AF point on the bird’s head. If the AF point falls on the wingtip of a large bird, the head will be out of focus.

Cameras that have an external AF-S/AF-C/MF switch (like higher-end Nikon DSLRs and this Pentax K-5) make changing modes with the camera at your eye easy. Many mid- and high-end DSLRs have a programmable thumb-operated AF-on (or AF-lock) button on the back. You can set this so it activates AF and locks focus when released, or so it locks focus when pressed, either way allowing you to stay in continuous AF mode for both action and static wildlife shots.

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If absolute fastest AF response is required, use only the center AF point. With lower-end DSLRs, activating all the AF points can slow AF performance noticeably as the camera’s processor has to deal with information from all the points. In this nine-point system, there are big gaps between points.

“Ballpark” The Focus Manually
3 Set the focus in the ballpark manually before activating AF. That way, the AF system will lock onto the subject much more quickly, with no hunting, and you’ll be ready to shoot much sooner. If the lens is focused near its minimum focusing distance and the subject is about 150 feet away, the camera may never achieve focus, and the image will be so out of focus, you may not even be able to find the subject when you look through the viewfinder. In keeping with the above, a vital feature of a bird-in-flight lens is the ability to prefocus manually while in AF mode. Canon USM lenses with focusing scales allow this, as do Nikon AF-S lenses, Pentax SDM lenses and Sony’s 70-400mm SSM zoom. If you have to switch to manual mode to prefocus manually, that will slow things down considerably.

Use Continuous AF
4 Use continuous AF for action shots obviously. Put focus in the ballpark manually, position the AF point on the subject, then partially depress the shutter button or the AF button to activate the AF system (see Tip #8: Program The AF Button). Pan the camera to track the subject, keeping the AF point on the desired spot, give the system a moment to do its thing, then fully depress the shutter button to make the shot. Don’t stop panning as you depress the shutter button; follow through.

Use The Focus-Range Limiter
5 Use the focus-range limiter on your long lens if it has one. Most animal action occurs far enough from you that you don’t need the lens to focus through its entire distance range, and having it do so slows down the process greatly.

Switch Off The Stabilizer
6 Image stabilization works best with stationary subjects or subjects moving at a steady rate in a steady direction. For erratically moving animals like flying birds, stabilization actually will fight you as you track the bird, and that doesn’t lead to sharp images. Stabilization also takes time—up to an additional second with some stabilizers. When you need the quickest response, you’ll get it with stabilization turned off.

Some feel that stabilization helps the AF system perform better, so it won’t hurt to try wildlife action shots both with and without stabilization, and see which works best for you with your gear.

Select The Focus-Change Delay
7 Some DSLRs let you choose how long the camera will wait to refocus if the focus distance changes abruptly. This is handy if a bird subject briefly flies behind a tree or if you let the AF point momentarily slip off the subject. If you set a longish delay, the camera won’t try to focus on the tree or background immediately. If you set minimal delay, the camera will immediately try to focus on the tree or background. I usually leave this set for “normal,” but you can experiment with your camera to see what works best for you. If the camera does lose focus on the subject, immediately let go of the shutter button, manually reset focus in the ballpark, then press the shutter button halfway down to activate the AF system again.

A side note: AF systems work best with subjects against a plain background. I have yet to use a DSLR that was good at tracking a subject against a busy background. So try to photograph action subjects against plain sky or a large water surface rather than against busy foliage.

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Pro DSLRs have more AF points, but you’ll still get quickest AF performance with only the center point active. The center point is also generally more sensitive than the others.

Program The AF Button
8 Many action photographers like to separate AF activation from the shutter button, switching the function to the rear AF-on button. Most AF SLRs will let you do this via a custom function. That way, you can activate focus by pressing the AF button and stay in continuous AF mode at all times, releasing the rear AF-on button to lock focus on perched birds. Note that with some cameras, the AF-on button won’t activate the image stabilizer in the lens although, as pointed out in Tip #6: Switch Off The Stabilizer, I don’t recommend using the stabilizer for flight shots.

Switch Off The AF Illuminator
9 The AF Illuminator is effective only out to around 10 to 12 feet. You’re not likely to be doing action shots at that range, and the illuminator slows things down, so switch it off. Besides, if the light level is so dim that the illuminator fires, you’ll be doing slow-shutter blur effects anyway, not sharp action shots.

Use Manual Exposure Control
10 Today’s AE systems are almost instantaneous, but for quickest response, preset the exposure manually. As a bonus, if you preset the exposure manually for the subject, you won’t have to worry about the meter being fooled as it travels across bright and dark backgrounds. Having to determine and set and reset exposure compensation while tracking a quick-moving subject doesn’t help produce sharp action images.

Use The Right Shutter Speed
11 Normally, you’ll want to use a fast enough shutter speed to sharply “freeze” the subject in the image; generally, this will require 1⁄1000 sec. or faster. However, this can vary depending on the subject’s speed and direction of movement and the shooting distance. You may want to experiment with different shutter speeds, including slow-shutter blur effects, both handheld and with support (see Tip #15: Try A Camera Support).

Try A Higher ISO Setting
12 Most lenses are at their best a stop or two from wide open, e.g., ƒ/5.6 or ƒ/8 for an ƒ/4 lens. This also provides a bit more depth of field to get more of a large subject sharp. But you also need a fast enough shutter speed to stop the action and to handhold a long lens. Most current DSLRs can produce excellent image quality at ISO 400-800, which provides some leeway for lower-light situations, although ISO 100-200 generally produces the best image quality with most DSLRs.

Experiment with different shutter speeds, ISO settings and apertures from wide open to two stops down from there, and see what works best for you.

Set The Advance Rate To Suit The Subject
13 High-speed advance gives you a better chance of catching that perfect moment, but low-speed advance gives the AF system more time to nail focus between shots. You’ll have to see which works best for you with your camera. I sometimes use high-speed advance, which is 6 to 10 fps with my cameras, and sometimes low-speed, which is 3 to 5 fps with my cameras. Either way, fire short bursts so you get a variety of “decisive action moments.”

Shoot JPEGs For Quickest Response
14 If shooting speed is paramount, shoot highest-quality JPEGs instead of RAW images. No, JPEGs aren’t as “good” or as versatile as RAW files, but they’re much smaller, and with some DSLRs, that translates to faster shooting and more shots per burst. For example, the Nikon D300S can do 7 fps when shooting JPEGs or 12-bit RAW files, but only 2.5 fps when shooting 14-bit RAW files. Due to their larger file size, RAW images also limit the number of frames you can shoot in a single high-speed burst (18 to 30 RAW for the D300S versus 44 to 100 Large JPEGs).

Try A Camera Support
15 Many bird-in-flight photographers, myself included, work handheld. A good number of others use some form of camera support. The BushHawk is a rifle-like support that works very well for flight shots and is easy to carry around. For flight shots from a tripod, a gimbal head is a necessity. This device can be locked down for rock-steady still shots, and unlocked, it provides the ability to track moving subjects smoothly while still lending good support. Many serious bird-in-flight photographers use gimbal heads for flight shots with really long lenses. Popular brands include Custom Brackets, Flashpoint, Induro, Jobu, Kirk, Manfrotto and Wimberley. For non-bird wildlife action with a long lens, a tripod with a gimbal or ballhead is de rigueur.

Action AF Workflow

Here’s how I photograph birds in flight:

1 Acquire the bird in the viewfinder.
2 “Ballpark” focus on the bird manually.
3 Position the center AF target on the bird, and activate AF by pressing the shutter button halfway down.
4 Track the bird with the camera, keeping the AF point on the bird.
5 When the image looks sharp in the viewfinder, fully depress the shutter button to take a quick burst of images.
6 Continue to pan with the camera to track the bird until a couple of beats after the last exposure has been made.