Understanding back button focus

I can see how being a left eye shooter could make it a little awkward. Sony have their own version. Obviously Nikon set it up slightly differently. Canon have 4 options in the custom settings on the 1D MkIV. From default shutter doing everything through stopping AF by pressing BB to the way I use it and finally disabling the BB completely. You can also change all these options to the AE lock button.

It's whatever suits you. It takes a little time to get used to it. It may not be suitable for your type of photography.

As I've said previously I like the option of separating exposure from AF. It also means that I can keep the AF in AI- Servo all the time so it's always available if I need it.
 
Martyn... said:
When the wife offers to take my photo on holiday ... despite the clear instruction "press this button to focus" :D
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Haha, to be fair my wife now knows how it works but other people using the camera is the only problem I have encountered.

In the delivery suite with my wife holding our 2 minute old daughter and the midwife offered to take a photo of the 3 of us. It was almost dark in there and I hadnt brought a flash, ended up with my arms around her and focusing on the Mrs at f1.8 and quickly running round to get in shot whilst telling the midwife not to move!
 
dave_bass5 said:
Wouldn't the focus change with most lenses if you change the FL with the zoom?
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With most yes.

However I don't use 'most' lenses - seriously, plenty of good lenses only change focus a little when you zoom, and at F8 and those distances it's not an issue.
 
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Phil V said:
With most yes.

However I don't use 'most' lenses - seriously, plenty of good lenses only change focus a little when you zoom, and at F8 and those distances it's not an issue.
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Well yes, but i think it needed clearing up as we are talking basics here and not everyone would know that. I doubt the OP would know he has a lens that can or cant do it (no offense meant to the OP of course).
 
artyman said:
It's for occasions that you hand the camera to someone inexperienced with BBF that you use the green box setting :D
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Never thought of that. Good call! Although isn't it more important to shoot RAW if you're handing the camera to someone who doesn't know what they're doing?!
 
Phil V said:
With most yes.

However I don't use 'most' lenses - seriously, plenty of good lenses only change focus a little when you zoom, and at F8 and those distances it's not an issue.
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Interesting. I always refocus when I adjust the zoom, even by a little bit. Is that not necessary then?
 
Goody13 said:
Interesting. I always refocus when I adjust the zoom, even by a little bit. Is that not necessary then?
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Whether its necessary would be dependant on DoF and your lens.
 
Fair enough. My main lenses are a Sigma 17-70 and also a Canon 70-300IS. Naturally, the aperture I would use would vary.
 
Well as an update from my original posting of this question, sunshine was out so armed with my 650D set to BBF off I went on my walk.

I found it so much easier to use the camera in this mode, as I found the focus was snapping in quicker and sharper than when I held the shutter button down previously, and I now had the benefit once focus was set of experimenting where the metering was being read from, and then recomposing.

Was very pleased with the results so guess I for one will be continuing with BBF in the future.

Thanks to one and all for the input into what has been a very interesting thread.
 
PJ S said:
Should've bought an EU version, as they're designed for left-eye use, just like their cars are designed for left-hand drive.

Simples! :bonk:
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IMG_5346_Simon_crop_TP.jpg


Yep, get a left handed one like I did!
 
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I have been following this discussion with interest. I tried it on my d90 + cheap 3rd party grip, all was fine until i took a shot in portrait & the button on the grip wouldn't work. Does anyone know if it could be just my grip? (exposure lock works fine with this button )
 
corbystock said:
I have been following this discussion with interest. I tried it on my d90 + cheap 3rd party grip, all was fine until i took a shot in portrait & the button on the grip wouldn't work. Does anyone know if it could be just my grip? (exposure lock works fine with this button )
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Check the menu. Nit sure if d90 is the same but on the d700 you dictate the behaviour of the grip buttons separately to the main body buttons. It could be that your grip AF-on button is set differently to the main one.
 
It takes a while to get used to but once you do you may never go back, i know i wont.
 
I know this is an old thread, but with a few eyes on it once upon a time I thought this recent video release might give a clear demonstration of the benefits....


Of course, the video only gives one example use case, but the benefits can be applied to any situation where it is convenient to switch from focus recompose one moment to servo tracking the next and back again. e.g. a bird on a branch which then takes flight and later lands again. Or perhaps you are street shooting and wish to switch from static subjects to approaching ones and vice versa without constantly fiddling with camera settings. It also means you can carry on shooting through a temporary obstruction without focus being drawn to that obstruction (e.g. a fence, lamp post, branches of a tree, competitor, spectator, passer by etc.).
 
tdodd said:
I know this is an old thread, but with a few eyes on it once upon a time I thought this recent video release might give a clear demonstration of the benefits....


Of course, the video only gives one example use case, but the benefits can be applied to any situation where it is convenient to switch from focus recompose one moment to servo tracking the next and back again. e.g. a bird on a branch which then takes flight and later lands again. Or perhaps you are street shooting and wish to switch from static subjects to approaching ones and vice versa without constantly fiddling with camera settings. It also means you can carry on shooting through a temporary obstruction without focus being drawn to that obstruction (e.g. a fence, lamp post, branches of a tree, competitor, spectator, passer by etc.).
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Thanks for resurrecting this thread. For me it's the most useful thread I have read on TP.
 
But what is the argument against using the shutter release to focus using continues focus and just pressing the focus lock button to lock the focus when required (and recompose),it is the same button just being used to lock the focus rather than cause focus?
 
shapeshifter said:
But what is the argument against using the shutter release to focus using continues focus and just pressing the focus lock button to lock the focus when required (and recompose),it is the same button just being used to lock the focus rather than cause focus?
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It's an extra step?
Press-focus
Press-lock
Press-shoot

Whereas BBF is
Press-focus
Press-shoot

And the difference between continuous and single shot is subtly just done.

And you don't need to have to keep thinking did I lock it?

And how would a refocus work? More button presses?
 
As well as the benefits of BBF in focusing, I really like being able to lock exposure easily with the shutter. This is great for stage and events.

I set metering on 3% centre and point at what I want to meter from and lock with a half press.

I can then continue to BBF, compose and shoot and matain that same exposure for as long as I need it. It takes a little practice, but it gives great control.
 
Yes I see.Thanks for that,it had not been pointed out in the thread even though both methods had been mentioned.
 
shapeshifter said:
Yes I see.Thanks for that,it had not been pointed out in the thread even though both methods had been mentioned.
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I've mentioned it before, but people had a ball at one of Garry's studio days watching me trying to use a Nikon set up to focus with the shutter button:oops: :$.

Brought up on manual focus cameras, I don't make any mental link between the action of focussing and the action of shooting. So having them completely independent just feels 'right'. I appreciate that most people grew up with AF, but using the shutter button to focus still seems wrong, particularly as I could never predict when it's going to try to refocus, it's counter intuitive to have to tell it not to focus:(, surely it should just focus when I want it to?
 
I switched to BBF when I upgraded from the D7000 to the D810 as there was a single button I could use.

Doubt I'd go back to "Normal" now. Its just every now and then I keep checking I've not flipped the AF/M switch because I forgot.

Just shows I need to get out more
 
Going to switch mine to BBF and see how i get on. Could of done with it last week at British Super Bikes now I think about it.
 
Good thread, thanks. I use it often, usually when it's a moving subject but I've learned some new stuff on this thread too, so thanks for that :)
 
Am going to start doing this but have couple of questions:

-using AF-lock when does the camera meter? What do I do if I want to meter somewhere other than the area of focus? Dial in exp comp?
-whats the point of using continuous focus when usung bbf?
 
Darthchaffinch said:
Am going to start doing this but have couple of questions:
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-using AF-lock when does the camera meter? What do I do if I want to meter somewhere other than the area of focus? Dial in exp comp? However you want, depending on your camera, you can assign exp lock to a different button, or you can set it not to lock, or you can do it with the shutter half press.
-whats the point of using continuous focus when usung bbf? Whilst it makes more difference in single shot situations, it works great in continuous too.
 
Thanks Phil (and apologies as this info must be buried somewhere in the bbf threads!), last question- if I'm doing this with a moving subject is it better to track the subject with bbf held down, burst shoot as the subject moves through a preset focal plane?
 
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Darthchaffinch said:
Thanks Phil (and apologies as this info must be buried somewhere in the bbf threads!), last question- if I'm doing this with a moving subject is it better to track the subject with bbf held down, burst shoot as the subject moves through a preset focal plane?
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if I'm doing this with a moving subject is it better to track the subject with bbf held down, burst shoot
Yes
as the subject moves through a preset focal plane?
Not necessary, as the camera will be tracking the focus in continuous focus mode
 
About a year ago I started using BBF full-time.
Explaining why might be relevant to this thread.

Initially I started using BBF for photographing bands playing on stage at festivals.
It's a classic use of BBF as most of the time you know exactly where they will be (at the mic), so pre-focus using BBF and then wait patiently for the expression / action that makes the shot.
It works well, but flipping in and out of BBF is a pain and I often forgot to focus while taking other shots around the festival site.

I next experimented with BBF using very shallow DoF telephoto lenses for semi-candid coverage of local events (135mm f2).
The challenge is that I have a knack of taking images when people blink; it seems to be caused by me waiting for a flash of expression crossing their face, and evidently this is often accompanied by a blink. Sometimes 2 out of three shots will have their eyes closed.
Hence I like to take several shots before moving on, but focus and recompose can be a PITA when the light is poor as getting focus in the right place can be unreliable.
BBF solves this, providing I keep a watch for them changing their distance.
As said earlier in this thread, when the subject is moving keep your thumb on the BBF button and frame the image so the AF point is on their eye; it works a treat.

Having got as far as deciding BBF worked for candids, and a lot of my landscape shots are in manual focus anyway, I decided to try going full-time BBF.
The hardest thing has been remembering to use BBF with lenses and subjects that don't need it; e.g. walkabout with the 24-105.
I've stuck with it for about a year now, and it is becoming increasingly natural to mash the BBF button.
When I'm tired, stressed or drunk I occasionally still forget - but I'm getting there.
 
To take this a step further, on my Canon I can customise the AE-LOCK (the button with the star icon) to toggle between SINGLE SHOT and AI-SERVO (continuous).

So, in having my AF-ON button as Back-Button-Focus I can also easily slide my thumb to cover both buttons at once. This can be very useful when a perched bird suddenly decides to fly, says he who nailed the perched shot of a Little Egret recently but missed it taking flight! - My excuse was a couple of women coming up behind me and asking me questions - WTF did they think I was doing lying on the ground in camouflage! If they had been attractive I should have pretended I was injured and needed a kiss-of-life.

It took me a few sessions of shooting to get used to BBF without thinking about it on my Canon 70D but now it's totally natural and on by default on my 7D Mark II.
 
With a nikon why not just use a1-a2-a3 in the menu
a1 and a2 focus priority and
a3 focus tracking with lock on?

that is on the Nikon D800
 
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