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Dumb question re: AF-On button on D2X

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According to the manual the AF-ON button serves the same function as pressing the shutter realease button 1/2 way. But my dumb question is, "Why would I use this?" What purpose does this serve and in what instances would I use this over pressing the shutter button 1/2 way?

Thanks.
 
The reason I like to use the AF-On button is because it allows you to focus and be done. When you press the shutter release there is no chance your camera will refocus.

This is very nice for landscapes...or even for photographs of fidgety children who are just wiggling.

Because your focus is fixed when your hand is off the AF-on you can also take your time and check things like depth of field, etc. It also replaces having to push the focus stop button on some of the long lenses like the AF-S 70-200 VR or the AF-S 80-200 or the AF-S 300 or the AF-S 500. Much easier to just take your finger off the AF-on button.

One other reason is that it will keep your focus from jumping if you jerk your trigger. It makes sense to have the release button just do one thing. The half-way down thing is really a left-over from point and shoot days.

I just recently transitioned to this mode in the last couple of weeks. Ron Reznick was trying to get me to do this two years ago...I've never known him to be wrong, but I guess I was trying to be obstinate.

Regards,

Paul
--
The grand essentials to happiness in this life are something to do,
something to love and something to hope for. - Joseph Addison
 
Paul described it pretty good. It is useful only when you set the camera so the release will not activate the AF. There are many situations where you don't want the camera to refocus all the time. It is a better alternative than holding the AF-Lock button all the time.

It is a very nice feature if you get used to it. I tried it many times but can't adpat to working like this.

--
-------David-------
http://www.pbase.com/david_hofmann/root
 
I'm trying to convert to this myself. I like to prefocus on something and then recompose for the final picture. When I recompose, the focus sensor is usually over something I don't want to focus on or worse yet, nothing (wall, sky, etc.). If I'm careful with holding the shutter halfway down while I wait for the action to happen, I'm fine but while I'm waiting, sometime I lift just enough to unlock the focus. Then when the action happens, I miss the shot because it's got to refocus and the sensors on the wrong thing.
 
paulfrye said:
The reason I like to use the AF-On button is because it allows you
to focus and be done. When you press the shutter release there is
no chance your camera will refocus.

This is very nice for landscapes...or even for photographs of
fidgety children who are just wiggling.

Because your focus is fixed when your hand is off the AF-on you can
also take your time and check things like depth of field, etc. It
also replaces having to push the focus stop button on some of the
long lenses like the AF-S 70-200 VR or the AF-S 80-200 or the AF-S
300 or the AF-S 500. Much easier to just take your finger off the
AF-on button.

One other reason is that it will keep your focus from jumping if
you jerk your trigger. It makes sense to have the release button
just do one thing. The half-way down thing is really a left-over
from point and shoot days.

I just recently transitioned to this mode in the last couple of
weeks. Ron Reznick was trying to get me to do this two years
ago...I've never known him to be wrong, but I guess I was trying to
be obstinate.

Regards,

Paul
--
The grand essentials to happiness in this life are something to do,
something to love and something to hope for. - Joseph Addison
Click to expand...
Great explanation! I'll say this, I could never get used to doing this until I used if for awhile with a good prime. Don't get me wrong, it's not for everyone but if you want to learn it quickly then just slap on your favorite prime and force yourself to shoot like that for a few days. The transition back to a zoom is very easy afterwards.

Everyone is different but for me it just seems natural that the camera is setup this way. The focus is one thing, composition something else. It really speeds up things for someone that thinks that way.
--
Not a pBase supporter.
http://darkangel.smugmug.com/
 
When I say slap on your favorite prime, pick something that is relatively fast (2.0 max apeture or better) and shoot with it wide open with your new setting. When you are shooting a normal lens or mild telephoto wide open where focus is going to be more critical then you'll quickly see the advantage of this.
--
Not a pBase supporter.
http://darkangel.smugmug.com/
 
While I obviously don't have a problem with you converting to this form of focussing, since this thread was based on the D2x and the D2x has a multiplicity of focussing sensors, if you want to focus on something that is not in the center, why don't you adjust the focussing area to be where you want the focus to be? That is what I thought Nikon was trying to enable.

Regards,
TED
Steve Ridges said:
I'm trying to convert to this myself. I like to prefocus on
something and then recompose for the final picture. When I
recompose, the focus sensor is usually over something I don't want
to focus on or worse yet, nothing (wall, sky, etc.). If I'm
careful with holding the shutter halfway down while I wait for the
action to happen, I'm fine but while I'm waiting, sometime I lift
just enough to unlock the focus. Then when the action happens, I
miss the shot because it's got to refocus and the sensors on the
wrong thing.
Click to expand...
 
I can't speak for Steve but personally (most of the time) I just find it easier to use the center sensor only and recompose.
Ted Johnson said:
Regards,
TED
Steve Ridges said:
I'm trying to convert to this myself. I like to prefocus on
something and then recompose for the final picture. When I
recompose, the focus sensor is usually over something I don't want
to focus on or worse yet, nothing (wall, sky, etc.). If I'm
careful with holding the shutter halfway down while I wait for the
action to happen, I'm fine but while I'm waiting, sometime I lift
just enough to unlock the focus. Then when the action happens, I
miss the shot because it's got to refocus and the sensors on the
wrong thing.
Click to expand...
Click to expand...
 
Ted,

You're right, but I found that when I moved the focus point around, unless I returned it to the center after a shot,for every shot I'd have to first find the focus point that was in use, determine if its appropriate for the next shot, otherwise move it again. Anytime I had to take a quick shot, either the focusing process would take too long and I'd lose the shot, or my focus point would be in the wrong place. With the AF-On button, I know the focus point is always in the center and I can set the focus and then not worry when I recompose. I keep my focus set on continuous and when I want to follow action, I just keep the button pressed.
Mike
--
http://www.pbase.com/mzelmar
 
Once I got used to using the AF button for focus it became very natural and use it for everything now. I feel using the shutter button for focus and exposure was one of the prime reasons people were having focus problems with the D70 in the beginning. Once they recomposed and pushed the shutter button it would refocus.
Jim
 
--Maybe i don't understand this, but what's wrong when i focus with the releasebutton, recompose (holding the releasebutton) and than tke the picture. It doesn't refocus (when teh button is on singlefocus)

as far as i know the small buttons on the 70/200 and other lonfaf-s/af-i lenses are used for stopping focus even when the camera is in continiuous focus.

That is not solved with the af-on button at the back of the camera when it is in continious focus.

BTW the D2H has the same options as the d2x

Happy Shooting

alex from holland

http://www.pbase.com/alex28

'You don't take a picture, it's given to you'
 
One other advantage to using the AF-ON button is exposure. Sometimes you want to point the camera in one direction, acquire focus, then recompose in another direction where the light may be entirely different.

This way, you can let the shutter release button handle exposure for the scene you've composed, and not have to worry about focus changing again.

Best Regards,
Tom Marshall
 
Hi There

I realise that many disable focusing on the shutter release and use the AF/on button.

for me the AF/on button really is useless!

I've left focus lock enabled, and removed exposure lock from the release button - I then use the AE lock button to lock an exposure, recompose and use the release button to focus.

I guess it depends really on whether the exposure or the focus is likely to be more critical.

Still, the point, surely, is that the D2x offers all these options, which allows each of us to tailor the camera to work the way which suits us best.

kind regards
Jono Slack
http://www.slack.co.uk
 
Exactly. Old habbits die hard.
 
Yes, I'd prefer selecting with the focus area rather than recompose.

In some cases, however, even with 11 focus areas the subject you want to focus on may not match one of them for the composition you have in mind, so some slight adjustment (small recompose) is still required.

After I have the focus area on the subject, I lock it using the AF-ON rather than half-pressing on the shutter release button to get my finger free for other tasks like DOF preview.

Cheers,
steve
 
Not on my camera :)

Since switching to the AF-ON button a year ago after a RR seminar, there is no way I'd go back.

It is so natural to release and reset focus with just a touch of the thumb on the AF-On button.

Also....if you shoot VR lenses, it's nice at times to not have the VR activating before you're redy to take a shot every time you focus.
--
Jim
 
Jim

Could you elaborate on this. I have tried using AF-ON as RR recommends but when I use the 70-200/VR I am not certain when VR kicks in. I think its when you press the shutter release and not the AF-ON button.

Sree
jfenton said:
Not on my camera :)

Also....if you shoot VR lenses, it's nice at times to not have the
VR activating before you're redy to take a shot every time you
focus.
--
Jim
Click to expand...
 
I've been experimenting with the AF-ON button and realize that when it's pressed it locks the focus. I then press the shutter relase then take a picture. Does that unlock the focus and I have to press AF-ON again or is that focus still good? I can't figure out what "unlocks" it? Is the AF-ON button only good for one shot and when can I go back to using the shutter release button to focus?
 
Thanks Jim, this confims what I suspected. There is nothing about it in the literature, as far as I'm aware, so glad to get the confirmation. Good to see your lemons replaced by a good ??? (what would be the appropriate fruit metaphor here? ), i.e. 2X, at last.

Sree
 
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