Talk to me about Back Button Focusing and its merits.

[MonicaBH]

I learned of back button focusing a few weeks ago, and set up my Nikon D90 so that I no longer use the shutter button to focus.

But I'm going to be honest: I'm not really sure what the merits are. I've read and re-read, and something is just not clicking with me.

Break it down, please?

 

[MLeeK]

When you make focus a conscious decision instead of a by product of the metering and shutter firing you are more careful and more accurate.

 

[fjrabon]

To me, the biggest merit is in composition and shooting in servo mode.

It allows you to pick your focus point, let go of the button, and then compose the shot how you want. Further, if you're following some action, but something gets in between you and the subject briefly, you can take your finger off the back button and you'll still be roughly focused on your subject, and then push back down when the intermediate object clears to begin follow focusing.

At first its just a pain more than anything else, but thats just because you're breaking the old habit.

Further, it also allows you to use spot focus a lot more, since you can easily move your camera around a bit, let go and then have your focus locked down. This lets you get away from matrix focusing.

 

[Robin_Usagani]

I learned of back button focusing a few weeks ago, and set up my Nikon D90 so that I no longer use the shutter button to focus.

But I'm going to be honest: I'm not really sure what the merits are. I've read and re-read, and something is just not clicking with me.

Break it down, please?

Lets say your subject is tiny and not in the middle. You point it to the subject, focus, recompose, press the shutter. When you press the shutter it wont change the focus. Basically you have more control on the camera to tell it when to focus. It is also good if you like to stitch a lot. You focus once and all of your shots will be the same focal plane.

 

[Robin_Usagani]

Also good if you lock focus in the dark. Once you get the focus, you really dont want the camera to hunt the focus again every shot or you will get a lot of blurry ones.

 

[Majeed Badizadegan]

I use the half-press of shutter for metering. I back button focus + Ai Servo + spot select focus, which gives me ultimate control over:

1. focusing
2. re-focusing
3. metering

Instead of the half-press shutter metering and focusing, why not take control of this critical element to improve your resulting photos? I almost never miss focus because I shoot this way. This level of control becomes especially important to me at wide apertures and close working distances, where DOF can be less than one inch.

Precision is the name of the game.

 

[kathyt]

I use BBF and it think of it as my ONE main button that is responsible for my focus. I focus and recompose. I do not toggle between my focal points. I have noticed a huge improvement in my focus issues since switching to this about 6 months ago. You do have to be careful though if you do change focal planes that you have to re-focus on your subject. I will say it did take some getting used to especially if you have been shooting for awhile and just using the shutter button to lock focus.

 

[Derrel]

It separates the focusing function from the shutter release button. At times, not all the time, but at certain times, it's best to allow the AF system to carefully determine the exact focusing distance, and THEN, to LEAVE IT SET at that distance, so that you the photographer, can devote attention to pressing the shutter release at a specific, "right" time. Much of the time this involves pre-focusing, because the action will occur at a specific spot, and your job is to WAIT for the action, then shoot it, or because it is slow, or difficult, or tricky to actually GET a good, accurate focus lock, due to whatever factor(s).

Back button focusing varies a bit with the level of camera. In the pro-level Nikons, there are actually TWO thumb button controls on the back; the combined AE-L and AF-L button, and the AF-ON. There are MULTIPLE combinations of how these three parameters can be set up to interact with one another. The "consumer" level cameras have a simpler set-up. Older Canons had no dedicated button, but instead used a Custom Function menu modification to turn the "*" (the so-called asterisk button) into an AF button. I beliece it was with the EOS 30D that the consumer Canon's got a dedicated AF-ON button, but perhaps that appeared with the EOS 40D?? Can't recall exactly. Anyway, under "some" scenarios, it's handiest to have the thumb button on the back set and then LOCK the focus once you let go; other times, you might want it to focus, with no lock, each time the button is pressed. This is critically important to remember--because it one does it wrongly, things can go south in a hurry.

The whole subject of BBF is too complex to go into here at much length. One concept though is the idea that the focus can be set by pressing a thumb button, then allowed to STAY at that distance, and then the camera's light meter can be allowed to "run free" as it were, without locking or "linking" both the metering area and the autofocus together using the normal shutter button half-press method that is the default. Of course, on some cameras, for some scenarios, it's advantageous to have the focus distance AND the light metering LOCKED TOGETHER, so that one can focus precisely AND take a meter reading and lock both of those parameters, and then re-compose and use the shutter release button ONLY to release the shutter and capture the shot--the focus AND the light metering having been done ahead of time, and neither parameter associated with the timing of the shutter's release.

 

[JAC526]

I recently set up my 5dc for back button focusing and could not be happier.

It is so nice to have focus independent of shutter actuation. Best thing ever.

 

[SCraig]

I tried it on my D90 and I could not find any advantage to it whatsoever. Having a D90, I prefer to move the focus point around because metering is biased to the focus point. Sometimes a small amount of movement is all that's needed to go out of focus. Therefore, I want focus to occur immediately before the shutter opens. That's gives me the best sharpness. Frankly, it just seems silly to me to always use two buttons to take a picture so that, once in a while, I don't have to focus. For the one time out of 1000 that I don't want the camera to focus, I just flip the AF/M switch.

I also find that trying to keep my thumb on the AE-L button while trying to shoot fosters a poor grip, making shooting more susceptible to camera shake.

I have to agree with this. I tried it once, saw no advantage, and went back to the way it was. I prefer to have that button lock exposure as opposed to focus.

I can't see any difference in back-button focus and just using the shutter button to lock the focus. Set the focus mode to AF-S, press the shutter button halfway down, and the focus stays locked regardless of how you recompose the shot. Is that not exactly the same thing? Maybe I'm just dense but I honestly don't see any difference.

 

[Dikkie2]

What about people with a D7000 for example. They don't have that extra AF-on button.

They can add the AF-on function on the AE-AF-lock button, but then they cannot AE-lock anymore with that button.... Unless they add the AE-lock function to the fn-button....

That way, you use 3 buttons to make your shot :er:

 

[brian_f2.8]

When I shoot PGA I turn on back button focusing.in no way can I hit a shutter early. It's a nice feature. Once you get use to it you will set all of you cameras up that way.
At first I didn't like it but it took a little while. Try it out you don't like it then go back.

 

[shaylou]

When you make focus a conscious decision instead of a by product of the metering and shutter firing you are more careful and more accurate.

I'm not sure what you mean by that. You are still doing the exact same thing (pushing a button) it's just located in a different place. What does "a product of metering and shutter firing" have to do with it? Or mean for that matter?

 

[shaylou]

Wow I can't believe all the long drawn out replies to this subject. Let me start be saying that I set up bbf on my 5DIII and its still on as we speak. However there is no difference other than location of the button and half press vs full press of that button. It does however allow me to make exposure adjustments wail holding focus but that's it. All these long drawn out conclusions are misleading to an op that truly is looking for guidance. Go to the forum -talk photography- and search the same question if you don't believe me.

 

[Garbz]

It has nothing to do with it. Some people just think using a different button or a tripod, or (insert other non standard thing here) makes them better and slower. Either that or he's never heard of AF-S or realised that the Auto/Manual switch is conveniently located on the left thumb on many cameras.

I use back button autofocus only in a scenario where I want my camera to not focus every shots. Dark cityscapes are a classic. But even then these days I find It's just faster to focus using the shutter and then flick the camera to manual which is easier than digging through the menu looking for the AF-ON only option.