Photography Education: Back Button Focus - What, When, and How

Welcome to the first installment of my weekly photography education series. Each week I will touch on a photography related educational subject. This week we are going to cover the basics of back button focus. What it is and why/when to use it. I should mention this week’s lesson is geared toward DSLR Cameras.

Back button focus is essentially taking the focus action and separating it from the shutter and assigning focusing to another button (usually the AF-L Button). Leaving the shutter to do one thing, snapping that shot. Most cameras are set up to focus when you half press the shutter or as you press the shutter. This means that every time you press the shutter, the camera will generally attempt to focus or check for focus (unless of course you have it on manual focus). So lets discuss the reasons as to why a photographer may want to switch to back button focus.

Nikon d750 photo here for reference (the AE-L/AF-L Button is where you set up back button focus)

1. You can switch between continuous and single focus on the fly

As long as you are pressing the button, your Camera will continually focus. This makes tracking a subject and taking a shot when you choose to take a shot easier. Don’t want continuous focus? Simply focus and take your finger off the button. You can switch on the fly between the two modes. The other benefit to this is that it is faster. The camera is not stuck attempting to focus until you tell it to, making follow up shots that much faster.

2. You can lock focus. Locking focus gives you a few advantages.

The first is that you can recompose a scene without moving your focus. The second is that you can lock focus on a still object (or section) in a frame and not have to attempt to refocus as subject matter changes. For example, your child is at a T-ball game. You could set focus on the T-ball stand and not have to refocus on the player or stand until something drastically changes or you tell the camera to do so. It could also be used in street photography to focus on an area, and catch people as they walk into the focused area (making shots fast without needing to focus on each subject as they move into the scene). In the studio, this means you could rearrange your subject or scene and not refocus for minor adjustments, barring you moving part of your subject matter out of your depth of field. Generally, this would all be done on a tripod, but as long as you do not have a fairly limited depth of field, you will have some leeway within it to hand hold.

3. Less confusion for the Auto-focus system and instant manual focus

By combining with single point focus, you can help reduce confusion in your camera autofocus system. Especially as you track your subject. It also means one can switch to manual focus by simply releasing the focus button (which the camera will not override until you tell it to do).

Who should use it?

Short answer, Everyone! Everyone can use back button focus. The primary advantage is that your camera focuses when you want it to, not every time you fully press, or half press the shutter. Many sports, marathon, and still life photographers I know use back button focus. That being said, nearly any style of photographer can benefit from it, those examples simply being some of the primary users I am aware of.

Sounds great! How do I set it up?

Each camera system has a slightly different method of enabling back button focus. Just search for your camera’s make and model and there should be a plethora of instructions on how to set it up. I do plan on doing posts at a later date to cover how to set it up on a Nikon D750 and D7100 as I own both cameras.

Have questions or comments? Did I miss something? Please join the conversation!