[Timd]

I'm using back button AF, but had to set up a user mode which uses the "conventional" half press auto-focus. My so-called "idiot" mode to allow me to give the camera (reluctantly) to others to use. I also set the AF to AFC.

[comprock]

I'm of the back button focus camp as well. I've not left it since spending a week learning to do it a couple years ago. I also use focus select mode in conjunction with AF-C. A champ.

[PDL]

My go-too soapbox issue.
I have used the AF button (OK button on *istDs) since 2005 when I discovered it.
The use of the term Back Button Focus came about from the Nikon/Canon people since they did not have a specific AF button back in the day. The K10D was either the first camera or one of the first cameras to have a dedicated button labeled AF.

On this forum I have used the term de-couple to describe what I am doing. As an FYI, all of the National Geographic photographers I have had the chance to talk to up close (six or seven of them) de-couple focus from the shutter button. In fact one of them said the only customization he did on his cameras (Canon) was to show histogram/blinkies and de-couple AF from the shutter button.

It comes down to who is in control - having the camera choose for you (shutter button) or you choose the subject to focus on (AF button). Ask our self why have a AF button if you do not use it to focus?

The Elitist - formerly known as PDL

[savoche]

Advantages:
you can effectively switch from afc to afs very easily.

You get access to the very fast exposure rate.

For complex focus operations such as picking a detail in a busy scene you can focus and take multiple shots without losing focus or hunting.

An automatic feeling of superiority when someone else uses your body and can't make it work.

Disadvantages:

Takes a while to learn and you will miss the odd shot when the camera doesn't respond as expected until you remember the thumb.

This, and it makes Quick Shift actually useful. No more shutter button AF ruining your manually and carefully adjusted focus.

[TER-OR]

I use it much of the time. Most of the time when I'm chasing insects.

My only gripe is that I tend to smudge my glasses when doing so...

[acoufap]

I always use shutter release button and af button decoupled. The reasons are already mentioned by others.

[audiobomber]

Half-press for me, and not interested in changing. When I switch to action shooting, I need to change other things besides just AF mode. My USER1 mode changes many settings, including:
- TAv mode with auto ISO
- Expandable AF point
- SR OFF
- Center-weighted metering
- Default aperture and shutter speeds, depending on the subject (1/1000S, f5.6 usually)
- Normally +0.5 EV, which I find helps for BIF and most sports.

Rotating the K-3 mode dial allows me to change to action shooting very quickly. The K-3 is the first Pentax camera that allows this level of customization in USER mode. I would not want to go back to K-5 switches, they are much too slow compared to the way I work now.

[Zafar Iqbal]

I've used back-button AF for about 1½ year and *just* changed back to focus using regular shutter release button. The back-button is now set to cancel AF and so far I like this better for my particular needs, which involves doing lots of candid shots.

[TedH42]

Used BBF for the last year. K5 and K3 - K3 is better at it.

I had to vote no, as there wasn't a "what's AF" option.

You're excused - your lenses speak for you.

[normhead]

I had to vote no, as there wasn't a "what's AF" option.

Looking at you lenses, I realize you don't have a single lens made in this Century....

This Century is 15 years old now....

I'm not saying you're old fashioned, I'm not sure why not, I'm just not.

[Kerrowdown]

You're excused - your lenses speak for you

That's a good thing... right?

[TedH42]

That's a good thing... right?

With your beautiful and honored lenses, you bet!

[Kerrowdown]

I realise you don't have a single lens made in this Century....

Aye, but I have bought some of them within that time frame, does that count?

I'm not saying you're old fashioned

I consider myself more to be like a fine cask aged whisky.

[Kerrowdown]

With your beautiful and honored lenses, you bet!

Ok, in that case then, thanks very much for your giving me my exemption ticket.

[amoringello]

Advantages:
you can effectively switch from afc to afs very easily.

You get access to the very fast exposure rate.

For complex focus operations such as picking a detail in a busy scene you can focus and take multiple shots without losing focus or hunting.

An automatic feeling of superiority when someone else uses your body and can't make it work.

Disadvantages:

Takes a while to learn and you will miss the odd shot when the camera doesn't respond as expected until you remember the thumb.

Tried BBF several times. Never saw any use for it, nor any improvement on ability to focus over half-press.
But the third item above makes a lot of sense. Hold focus and click multiple times without re-focusing. Brilliant.

Not sure though, how AF.S v.s. AF.C works differently with BBF. I'll have to look into that.
Of course, I can't seem to get AF.C/AF.A to do anything other than to focus anywhere *other* than what I want in focus. It actually seems to track away from the object I had *locked* in focus.