Autofocus question

[dan_ling]

I'm currently using the olympus OM2 and am considering purchasing an

autofocus SLR more for a comprehensive system than for the

autofocus, although i see its utility. My question is once I

autofocus can I tweak it manually, or do i have to switch focus

modes first?

[the_macman]

It works on at least 97% of Canon EF lenses (for the EOS system). Don't know about other

brands.

[todd peach seattle, washi]

Depends on the system and sometimes the particular lens. Canon fans tout that very thing as a superior feature on most (all?) of their AF lenses. With Nikon, you have to be using the AF-S line of lenses. AF-S used to mean "very expensive", but Nikon has introduced some less expensive AF-S lenses as well.

[markci]

It doesn't work on anywhere near 97% of EOS lenses. More like 60% of current lenses, and even fewer obsolete ones. In particular, it doens't work on most of the consumer zooms, nor or some of the older primes. All in all there are close to 20 current lenses alone that do not offer full-time manual focus.

[Ed_Ingold]

Nikon AF cameras have two modes: single-servo and continuous. If you use single-servo (default) the auto-focus takes place when initiated by the shutter release (half-way) or the AF button, then stops. At that point, you can manually re-focus any AF lens, standard or AF-S.

 

With AF-S (Silent Wave Motor, in lens), you can tweak the focus at any time.

[tom_montemarano]

You can do this with the Minolta Maxxum 7. It has a "DMF" custom function. Once the custom function is set you can tweak focus on any lens after AF is locked. It also has a push button on the back that lets you switch to MF when the button is pressed in and then switches back to Af when you release the button. I use this for manual prefocusing long focal length lenses.

 

Tom

[yakim_peled1]

<P> USM (Canon), AFS (Nikon), HSM (Sigma). All have it. It's called <a href="http://photonotes.org/articles/beginner-faq/lenses.html#ftm">FTM</a>. </P>

 

 

<P> Happy shooting , <br>

Yakim. </P>

[markci]

Edward has posted inaccurate information above. With regular AF Nikon lens you cannot adjust focus without switching to MF mode. Physically you can, but the mechanism is not designed for that. You are possibly damaging your camera.

 

Only AF-S lenses, of which there are only a few, allow full-time manual focus. And even then you can't do it "at any time." In single-servo mode you have to wait for the camera to finish focus, and you can't do it at all in continuous mode.

[ron c sunshine coast,qld,a]

Mark and Yakim are right

[steve_muntz]

Agree with Mark Ci, you could burn out the focus motor this way.

 

The Tokina 28-80 f2.8 PRO lens has a clutch on the lens where you pull the focusing ring towards you (about 1/8") and that puts it into manual focus mode. I'm not sure about other Tokina lenses, but I also know that the 80-400 ATX II doesn't do this.

 

A few non-AFS Nikon lenses have something similar to the Tokina - push a button and turn a ring to put the lens into manual focus mode. Three lenses (possibly more) have it: 20-35 f2.8, 85 f1.4 and 80-200 f2.8 AF-D, two touch version.