A short post about Back Button Focus

I am mainly a landscape photographer. My subjects don't often move around much. Consequently, for some time now, when I use auto focus, I've been using "Back Button Focus" on my Nikon D610. I think I've been using it since shortly after getting the D610. I like it.

Hey - why use Back Button Focus?

Most DSLRs (Digital Single Lens Reflex), as far as I know, allow you to press the shutter release half-way down so that the camera can focus on whatever is in it's cross hairs. Note that different cameras and different modes can cause the camera to focus at different areas of the image. I typically use a single focus and metering point so that's what I'll assume here.

When you press the shutter release half-way down and the camera locks in on the focus, you can then move the camera while still holding the shutter release half-way down in order to recompose your shot. For example you might focus on your significant other in the center of the shot and then pan a bit to get more of the Grand Canyon. Once you have the composition you like, you can press the shutter release the rest of the way to take the photograph.

That is pretty convenient, allowing the camera to focus on one thing and then to re-compose the shot after the camera has gained it's focus.

One problem with that technique, however, is that you have to keep the shutter release depressed half way in order to preserve that focus setting. If your finger slips off of the button you have to start all over. So what if you've panned a bit and then someone else steps into your shot? If you want to wait for them to leave, you've got to keep that button held down. 

In landscape photography I often want to focus on something, say a cactus in the foreground, and then re-compose. I may want to try 20 different compositions. And, I use a tripod for almost every shot I take (at least if I want them to turn out I do). Using the "normal" half-pressed shutter release can be a pain in the rear end (so can sitting on cactus).

Another issue with the "normal" focus is if you want to avoid camera shake due to the shutter release, for example if you use a remote release. If you have to hold the shutter release down part way and then trigger the shutter release it can cause unwanted vibration or motion into the camera.

This is where back button focus can help out...

What is Back Button Focus?

Back Button Focus allows you to configure a button on the back of the camera to use as a focus lock. It basically takes the place of the half-press action of the main shutter release button. You move your focus point(s) onto the subject as normal but instead of pressing the main shutter release button half-way to engage the auto-focus, you press the button on the back of the camera. Then, you can let go of that button - the focus will still be locked in. It won't change again until you press that back button again.

The cool thing about this is that you don't have to keep your finger on the button. The camera can even go to "sleep" - the focus of the lens won't be changed.

You can focus on your subject and take multiple images with different compositions and you won't need to focus on the subject again unless it moves. This is great for landscape photography where you can focus on a foreground object and as long as your camera doesn't move much (less than the depth of field) you can recompose without focusing for each shot. There is less time between each shot.

I use manual focus a lot too, but I still often will start with a press of the back button to get the lens either right where I want it or at least close and then I may focus slightly different for one reason or another.

Nikon D610 Back (Official Nikon Image)

How can I set up Back Button Focus?

Most DSLR cameras, at some level above the basic level, have a way to program one of the BUTTONs on the BACK of the camera to work as a FOCUS button. In the case of my D610, I use the "AE-L/AF-L" button, to the left of the rear thumb wheel.

You can usually find out how to set it up by doing a search on the web if your camera instruction manual doesn't outline it (or if you can't figure it out from your camera manual). Here's an example for the Nikon D610 Back Button Focus setup. 

Anything more you can tell me about this?

Luna the Barn Owl - most of him anyway

This subject is on my mind because of my outing at Arizona's Raptor Experience last weekend. I shot a number of images like this one - see anything wrong with it? When I got home I found a number of shots where the feet were cut off.

The problem was, I realized and figured out after shooting 400 pictures of raptors, was that I was setting my focus point on the bird's eye, using the back button focus, and not re-composing or even noticing that I was cutting off the toes of these fine feathered friends. 

I'll admit, it was a little nerve wracking at the shoot. I suppose the more you do it the better you get. But I was paying $190 for the trip to shoot the birds and that added some pressure. I rarely shoot animals successfully and that added more pressure. And the pressure prevented me from getting great shots. 

At one point, when we had some time with a flying hawk, I had to figure out how to get out of back button focus and to let the camera do it's job. Those photos turned out ever worse. I got zero usable shots of the hawk in flight.

My tip would be that, if you start using back button focus, it still is a good idea to practise the other auto focus modes of your camera if you have a chance. Especially if you know you're likely to be needing it at some point in the future.