Autofocus: not using shutter release

[nikonkev]

This is for users who own cameras that allow them to separate autofocusing from their shutter release. In other words, when you press the shutter release button halfway down - this doesn't autofocus, but instead, autofocus is set elsewhere on your camera.

On my D2X, there's an AF-ON button and you can set it so that the camera only focuses when you press AF-ON, instead of allowing the camera to autofocus with the shutter release button (or both).

My question is: what are the advantages/disadvantages to this setup? I'd like to hear why people disable AF on their shutter release button when taking photographs.

 

[Garbz]

I have a profile on my D200 which I called "night" the reason being is that while AF works with a tripod I may be forced to focus on something first and then take the photo after recomposing. It may also be too dark for manual focus too but if there is a light on in the distance I can AF onto that.

So I point my camera at that light and hit the AF-ON button. Then I can recompose and snap away without having to worry about flicking the focus switch around.

It's not a matter of disbelieve but a case of when depressing the shutter would hunt for focus when the focus was originally set, and a case of not wanting to constantly flick the focus switch from M to S and back to M.

 

[table1349]

My question is: what are the advantages/disadvantages to this setup? I'd like to hear why people disable AF on their shutter release button when taking photographs.

One of the biggest advantages I have with having my auto focus on a different button is for shooting sports. Fast action allows you to constantly focus with out A. accidentaly taking a shot you did not want and B. It allows constant focus thru the triggering of the shutter. When you use the shutter release for focus and shutter release there is are a few split miliseconds where the focus stops and the shutter triggers. This is time is reduced when using a secondary focus control. Basicly it is mechanical multi-tasking. It may not be much of a difference but enough to help capture a sharper image in tough conditions. This does however need to be used in what Canon calls AI-Servo mode. I believe Nikon calls it continous focus mode or something like that.

One down side is it eats batteries. You tend to focus through more of the action anticipating the shots that you want. Focus time increases dramatically. That is why I always have a second set of batteries for both my bodies and grips when ever I shoot sports. It does take a little getting used to, but with practice it becomes second nature and you learn to lightly trip the shutter rather than stab at it. Something I have seen a lot of new sports shooters do.

 

[DSLR noob]

I have my 20D setup to use a button that normally meters flash "*" ( I don't use flash anyway) to be my AF button. IT helps because you can point the camera at something, press the shutter halfway, meter, then point it at your subject(still holding the shutter 1/2way from the metering) and focus with my * buttron, then take the shot. I combine this with partial metering

An example of using this, (I use it daily, I'll give an example of what I did today). I was taking pictures of people wearing black shirts. And, due to the partial metering and them being in the center of some frames, the meter would overexpose because it thought the room was darker than it was, I would look at the wall to their left or right (this is called metering for ambient lighting) then I pointed the camera at them, focused, and took the picture.

 

[nikonkev]

Thanks for the input! I was able to find out much more extensively about this topic, thanks to another member on the board here who nicely sent a link to me.

Thanks again, all!

 

[shorty6049]

i was just shooting the eclipse tonight, and once i got a focus on the moon, i needed to reframe the shot and change a couple settings that i didnt realize were off. i used my mf/af button (just disables the autofocus while pressed, enables it when you let off on it) to hold the focus so i didnt have to refocus when i pressed the shutter button... same sorta thing, that button was just closer to my thumb than the custom AF button i have, so i went fo it first since it was about -1 degree F here...

 

[brileyphotog]

It may not be much of a difference but enough to help capture a sharper image in tough conditions. This does however need to be used in what Canon calls AI-Servo mode. I believe Nikon calls it continous focus mode or something like that.

I put my Nikon on AF-C for sports, unfortunately I don't a separate button, so I hold the shutter button halfway down and hit it when I need to. Battery life is a problem, as is the fact that sometimes your lens spazzes out since it is constantly refocusing. AF-C lets you hit the shutter when the subject isn't in focus (AF-S won't let you do that), so you end up with some blurry images, especially if you aren't using the best lens.

 

[nikonkev]

I put my Nikon on AF-C for sports, unfortunately I don't a separate button, so I hold the shutter button halfway down and hit it when I need to. Battery life is a problem, as is the fact that sometimes your lens spazzes out since it is constantly refocusing. AF-C lets you hit the shutter when the subject isn't in focus (AF-S won't let you do that), so you end up with some blurry images, especially if you aren't using the best lens.

If you meant "unfortunately I don't HAVE a separate button" meaning the AF-ON... you should, if you own the D80 - the button just may not be called "AF-ON".

I've got a D70s as my backup body and it has the AF-ON Only function in my custom settings menu. Half-pressing shutter will not autofocus. Instead, it is solely done by the AF-ON button (on my D70s, this button is coupled with AE-L/AF-L button and isn't called AF-ON, like it is on my D2X).

Just a heads up, if you're ever wanting to rid the AF when you half-press the shutter