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Photography Tutorial: Back Button Focus (Reprise)

by Erin Peloquin on February 23, 2012 · 10 comments

Back Button Focus is one of those intimidating photography techniques that we hear about and think they might help, if only we could figure them out.  In my opinion anyway.

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I wrote about BBF a long time ago and used it for a couple of years, but have drifted away from it lately. So I’m going to talk a little bit about when it’s helpful for me (personally) and when it’s not.

This Canon article is the classic authority on BBF, by the way.  It will help you Canon shooters enable this feature and will give everyone an overview of the technique.

Back Button Focus Background

With our cameras set to factory defaults, we press the shutter halfway and the camera sets exposure and focuses on the center part of the image.  That’s great for beginners and many advanced photogs too.

But, there are times when you don’t want to re-focus each time you press that shutter button.

You want your focus set on a certain spot, and that’s that.

  • For instance, think about a birthday party or sporting event where you want to focus on one person, even if people might come into your frame that would normally change your focus.
  • Or, what about if you intentionally want a blurred shot, like the image above?
  • And, if you like to get creative with depth of field on a windy day, you’ll want to take Auto Focus off that shutter button as well.  I want my depth of field to hit the same spot on my frame each time in the shot below, but if the wind blows the flower backwards, my focal point will change (without BBF).

  • Or, if you want to focus the old-fashioned way (by using the focus ring on your lens.  Gasp.)

When you want to take focus off the shutter button in the situations described above, you assign the camera to focus only when you press a button on the back of the camera.

There are two reasons I don’t shoot with BBF much anymore for my general photography:

  1. I shoot in Manual Mode full time (I set exposure when I want to set it, and it doesn’t change.  One of the reasons to use BBF is to separate exposure from focus.  Shooting manual accomplishes this.)
  2. I select my focal point manually using the “joystick” on the back of my camera.  When I press the shutter button halfway, focus is achieved over the point I selected.

You guys might remember from my  Camera Settings write-up on my 5DMII that I have BBF set to the C1 setting on my dial.  So, whenever I want BBF, I can quickly switch over to it.

When to Use Back Button Focus:

  • To set focus with the lens ring.  Canon’s lenses let you change focus with the lens ring without switching the AF/MF switch. If don’t have Back Button Focus enabled, pressing the shutter button will trigger auto-focus and will override this manual focusing that you worked so hard on.
  • To blur intentionally.  Same principles as above apply.
  • When it’s hard to achieve focus – think about low light situations where your camera might struggle to focus.  Once you’ve got it, you don’t want to lose it.
  • Macro photography – another hard-to-focus situation.
  • If your lens is a slow focuser, BBF can speed up your shots (of still subjects) because the lens won’t search for focus each time.
  • Waiting for a shot – think about your child on a merry go round.  Once you finally focus in the right spot, you don’t have to refocus every time she comes around.  This applies to any situation where your subject is moving in a predictable or repeating way.
  • Back Button Focus is often helpful for people who shoot Aperture or Shutter Priority.  Exposure changes each time you press the shutter in these modes, but you don’t necessarily want focus to change each time.
  • In general, any situation where you don’t want to change your focus each time you press the shutter button is a good candidate for BBF.

I like that I have the freedom to easily switch between back button focusing and shutter button focusing.  It’s nice to focus with the shutter because it saves a button press.  But it’s even better to be able to Back Button in those situations where it helps.

So, what do you guys think about this?  I know there are some die-hard BBF’ers out there.  Is there any reason you can think of for me to go back to full-time Back Button Focus?

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