Does Bird Detection AF Really Work?


We like to say that it’s not about the equipment, that a photographer with any camera can create great photos. And in most situations, that’s true.

Then there is bird photography.

To get the ultimate shots of feathered subjects, you need special gear: zoom lenses with a long reach, plus, ideally, image stabilization to compensate for the exaggerated movement caused by zooming in. You also need a camera body with a system focus that can lock onto such dynamic aerial targets.

These systems are enhanced with AI technologies. Some high-end cameras now even have Bird AF (autofocus) modes that identify and track birds, some with focus priority on bird eyes. Examples include Nikon Z9, Sony a1, Fujifilm X-H2S and OM System OM-1 bodies. Other models, like the Sony a9, include animal AF modes that look for animals and birds of all types.

These use the same detection principles as Face and Eye AF modes, but with the added complexity that birds and animals move faster than your Uncle George. An eagle pulling fish out of a stream for dinner isn’t going to stop and pose, or come closer to the camera if you ask it nicely (again, neither is George). But with the right gear and AI assistance, you can capture that moment in precise focus.

A golden eagle. ISO 500, 1/320 sec, f/4.5, @ 200mm. Daniel Hernanz Ramos/Getty Images

Related: Pro tips: 3 keys to taking better bird photos

How it works

A number of elements go into the proper functioning of Bird AF and Animal AF. In addition to basic autofocus systems, the camera must understand what it is looking at. Camera maker developers feed thousands of photos containing birds and animals (and cars, planes and other objects on some systems) to autofocus software and train it to recognize patterns similar visuals.

The software also requires fast hardware to process what the camera sees in real time. The image sensor absorbs an image of incoming light information, passes it to an image processor which determines if anything in the image matches the objects it understands, then directs the lens mechanisms to adjust focus on point. All of this happens in milliseconds. Then the sensor sends a new value of image data and the process is repeated so you get real-time tracking and focus lock when you decide to press the shutter button.

AF bird in nature

The technology is impressive, but does it work well in the field? I contacted two photographers I know to get their point of view. Hudson Henry photographs all kinds of subjects but has just returned from a workshop in Costa Rica where he carried a Nikon Z9 and an AF-S NIKKOR 800mm f/5.6E FL ED VR into the jungle to capture birds, monkeys and other elusive denizens. Mary Lu is the author of the book Master bird photography (Rocky Nook).

When I asked Henry about his experience on his trip, he emailed, “I can tell you [Bird AF] worked incredibly well, with the Z9 picking up just about every bird’s eye I reasonably sized in the frame.

Sometimes the functionality was usurped by areas similar to birds’ eyes. “There were lizards with big spots on the sides of their faces that tricked him,” he said, “and butterflies that had eye-like markings that wanted to lock like eyes, sometimes requiring unique point selection.But overall it was incredibly good for a wide range of birds and wildlife.

Nikon Z9
Bird detect AF is starting to show up in flagship cameras, like the Nikon Z9. Nikon

Read’s experience is with a Sony a9, which offers Animal AF, not specifically Bird AF. But she said the shift to technology has been substantial.

She wrote: “I find it difficult to disentangle the effects of the ‘animal eye’ feature from the general increase in the proportion of sharp shots I experienced after switching to the Sony a9 mirrorless Canon DSLRs three years ago. I get a lot more focus keepers in a burst of frames than I ever could have before the change. Sony’s tracking AF is amazing!

She also highlighted the importance of the Bird AF and Animal AF features for anyone looking to get into bird photography, writing, “Scroll through any nature photography forum online and it will be obvious that there has been a huge increase in great bird photos, including some amazing action shots, in recent years. The downside is that now the bar has been set so high. She now says the best way to stand out from the crowd is to get much more creative with compositions and lighting.

Get the shot

Both Henry and Read offered their strategies for using the autofocus features of birds and animals to capture their targets.

Henry wrote: “I use a hybrid AF method for birds and wildlife which I teach on my Youtube channel. Wide or small area AF on the shutter (much like a band in the days of DSLRs) for fast erratic subjects like birds in flight, with conversion to 3D tracking (Nikon’s standard subject tracking mode) the back button to track a subject you pick up anywhere in the frame. I program a front function button that converts shutter AF to single-point AF-C for subjects where eye detection is lacking and you need to direct the point. But I leave 3D tracking on the back button. Pressing function button 3 toggles the AF shutter button between wide area and single point this way.

A parrot.
Scarlet macaw. ISO 140, 1/125 sec, f/6.3, @ 800mm. © HudsonHenry

Related: The best cameras for wildlife photography

As with many photographs, a varied approach is needed depending on the circumstances. Read shared, “As a Sony a9 shooter, for me the important things are selecting the optimal AF area size and whether or not to use tracking. Because my subjects are usually moving, I generally use tracking: Flexible Spot Medium. I usually start with the AF area positioned in the center of the screen, but then move it around as needed for composition. For birds in flight where the flight pattern is extremely fast and erratic (think terns or swallows), “Tracking: Area” may work well, but [it works] better if on a clean background. Another thing to fine-tune the AF is via “tracking sensitivity”. Sony offers settings ranging from 1 (Locked On) to 5 (Responsive). I have mine set to 2.

Sometimes tracking isn’t necessarily better than good old-fashioned manual focus. Read wrote: “It’s not the best idea to photograph a bird against a busy background, especially if it’s small in the frame, but in that case try an even smaller AF area (that’s i.e. “Tracking: Flexible Spot Small” by Sony). Shooting through vegetation, which can give a nice vignette effect if done correctly, is another place where you would want to use the smaller AF area. You may need to turn off tracking to prevent the camera from focusing back and forth.

Happy beak hunting

Good bird photography always requires more equipment than your average camera body and kit lens. And of course, you have to put yourself in a position to photograph the birds in their habitats. But with Bird AF and Animal AF technologies in the latest camera models, you’re much more likely to end up with sharper keepers than in the past.


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