Back-button focus in wildlife photography

Back-Button focus – Wildlife Photography Tips #3

This article was also published in The Blue Bill, the Quarterly Journal of the Kingston Field Naturalists, Volume 67, No 1, March 2020.

If I had to pick a single technique that made a dramatic improvement to my capability as a wildlife photographer, I would choose Back-button Focus. It’s a technique used by professional wildlife and sports photographers, and can help you take your photography to a higher level.

It starts with the recognition that crisp focus is perhaps the single most important quality of a good photograph.

Autofocus

Because focus is so central to photography, camera manufacturers have developed ways to make it easier to get an in-focus image. Any camera produced in the last 20 years has the ability to focus automatically – indeed autofocus is the default option, and may have to be turned off if you wish to focus manually.

Autofocus is engaged when you press down on the shutter release. This happens so quickly some beginning photographers don’t even realize it is happening, but with practise most people learn that if they depress the shutter release halfway they can focus the camera without taking a picture.

Back-button focus

For most types of photography having the autofocus engage when you press the shutter release makes life easier – a single action both focuses the image and releases the shutter. Wildlife photography, though, has its own requirements and many wildlife photographers find that the simple shutter release/autofocus approach actually creates problems.

Instead they use back-button focus, where the autofocus function is disconnected from the shutter release and assigned to a different button.

I am not going to explain how to do this. Each camera system has its own way of assigning buttons, and you will need to consult your manual to learn how to make the change on your camera. Instead, I am going to explain why you might want to make this change.

Targets obscured by foliage

If you have spent any time trying to photograph birds in the wild I am sure you will have had this experience. You are trying to capture an image of a bird roosting in a tree within a tangle of branches, twigs and leaves. You can see the bird clearly, but frustration creeps in because each time you take a shot the camera focuses on a different one of the surrounding twigs and only occasionally on the bird.

For all the capabilities of modern autofocus systems, remember that they are not actually intelligent – they try to guess what you want to focus on but they are frequently wrong.

Back-button focus in wildlife photography
My eye sees the bird, but the camera decides that I want to focus on a vine.

Using back-button focus can solve this problem. You centre your camera on the bird and engage the focus. You may have to do this a number of times until the focus point is actually on the bird. In cases where there is a lot of background clutter you may even have to use manual focus. But the key point is this: once you are focused on the right point you can shoot as many images as you want without the camera trying to refocus each time. As long as you stay at approximately the same distance from the bird it will remain in focus. The camera will not be able to “help” by randomly changing the focus point.

Back-button focus in wildlife photography
Now that’s better. Sooty-capped Hermit, nr Monterrey, Casanare, Colombia, 5 Feb 2020

And even if you have to move slightly to get a better angle, if you engage autofocus again it will most likely zero in on the bird because it will be the closest object to the focus point.

I think you will find that once you try this technique you will be reluctant to go back to shutter release focus. Time that you might have wasted in focusing and refocusing can be spent on adjusting ISO and shutter speed and choosing the right moment to shoot.

Focus and reframe

Wildlife photographers often find that they want the focus point of an image to be off-centre. There are two main situations where this occurs:

Large or close-in target

Say you have a chance to see a Moose at fairly close range. You want to capture the whole beast in an image, without cutting off its tail or legs. But you also want your focus point to be on the eye, as tends to create the most compelling image. And not surprisingly, the Moose’s eye is at one side of the image.

Composition

You have a bird in your sights but you want to frame the image so that the bird is off-centre. You might want to better show its within its habitat, or to give it some open space in front of it, or just because people are more attracted to images where the main points of interest are off-centre.[1]

In these situations back-button focus is your friend. It allows you to focus on the desired point, and then without changing focus reframe the image by moving the camera until you get the result you want.

Back-button focus in wildlife photography
Purple Finch surveys his domain. Renfrew County, Ontario, Canada, 19 Jun 2019

Note that landscape and portrait photographers deal with this need by manually adjusting the camera’s focus point. In principle this would also work for wildlife photographers, but in my experience the focus and reframe method is much more intuitive and much faster to use. For subjects that tend to move suddenly and unpredictably I think it provides better results. Moreover it allows you to set your camera adjusted to centre point focus, which is the most accurate autofocus mode.

Continuous autofocus

For moving targets, such as a bird in flight, holding down the back button allows you to keep it continuously in focus while you wait the right moment to shoot – such as when it banks to show its upper wings. You can also hold focus on a stationary target, and you will be in focus when it pounces, takes off, or otherwise moves suddenly. Without holding focus the camera will need to refocus at the critical moment, with unpredictable results.

Back-button focus in wildlife photography
Battle is joined. Greater Prairie Chicken, Nebraska, USA, 2 Apr 2017

In principle you could also accomplish this by holding the shutter release halfway down, but in the real world of wildlife photography, where you will often be wearing gloves and your hands may be stiff from the cold, using a separate button removes the need for such fine motor control.

Of course you could just “spray and pray”, firing off twenty images at high speed and hoping one of them works. As long as you don’t mind everyone nearby assuming that you are clueless. 😊

Back-button focus – further advantages

While the above points are the key reasons for adopting back-button focus, there are a few minor advantages as well:

If you are using manual focus, you won’t then risk spoiling your own efforts when it’s time to press the shutter release.

Use of back-button focus reduces battery drain somewhat. Unlike shutter release focus it doesn’t automatically engage the lens’s image stabilization/vibration reduction motors.

The downsides?

Back-button focus is possible on most DSLRs and mirrorless cameras, but it may not be possible if you are using a bridge or superzoom camera. Check your manual to see if you can use this function.

And if you ask someone to take a picture using your camera, don’t expect great results. You can explain carefully the need to press the focus button and then press the shutter release, but I find that most people don’t “get” this and the images tend to be out of focus.

Other topics in this series

Wildlife Photography Tips #1 – Exposure Compensation

Wildlife Photography Tips #2 – Shutter Speed


[1] See https://en.wikipedia.org/wiki/Rule_of_thirds

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