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AF-On question

Discussion in 'Nikon DX DSLR Forum' started by Jason, Sep 16, 2008.

  1. Jason


    Aug 15, 2008
    St. Louis, MO
    I have my D300 set up so that I use the AF-ON button for focus only. I was just wondering about something I noticed the other day shooting. When I push the AF-ON button and release...I can then recompose and shoot, right? The main question is in the viewfinder...the "dot" that tells you when things are in focus comes on when I hit the button, but when I release it the "Dot" goes away. Does this mean that the focus is indeed NOT locked on target? Should the dot stay on even after I release the AF-ON button? I may have missed a setting when I set this up. The thread on the AF-ON button is where I learned of this.
  2. fivegrand

    fivegrand Guest

    my experience is that the green light indicating focus is only on when focus is actively working (when you're pushing the af-on button or half-pressing the shutter release).

    you could conceivably press the af-on button, getting focus, then roll your thumb over to the af/ae-l button to lock focus there, then recompose and release the shutter.
  3. The green dot will disappear because you aren't asking the camera anything at that juncture. It is like asking someone "What is your name" and they tell you "Bob". They don't keep repeating Bob - you have the info. In the same manner, the camera finds focus and thats that. You are essentially saying "Please get in focus and tell me when you are" and it answers "okay now". You have the information. Also - listen to the lens - if you don't hear it whirring - you know it still is where it last was when the green light came on confirming auto-focus.

    On a sidenote - unless you changed it - when you push halfway down on the shutter release, your camera focuses. So perhaps you may want to make sure your shutter-release does not trigger AF on the half-depress if you are going to be using the AF-ON (maybe you have the shutter release set for AE?).

    For D300 - Check settings A5 & C1 for AF & AE on the shutter release.

    (Jon, above, gives another alternative if you don't want to disable the shutter-release from default. You can get focus and lock it). Whatever makes more sense to you in your workflow.
  4. Jason


    Aug 15, 2008
    St. Louis, MO

    Thanks for the replies...I have it set right (thanks to the long thread on this topic). I just was not sure about the green light (dot).
  5. Yeah - you are all set. The green light going off is normal.
  6. MMarz


    Sep 15, 2007
    Long Island, NY
    To add to what was already said...

    If you have used the AF-on Button to lock focus on a particular spot, say an eye, confirm it with the focus indicator dot, then recompose, you shouldn't expect the confirmation with the dot because technically, as far as the body is concerned, you ARE NOT in focus since the active AF point is no longer on the eye. Also, by virtue of using Release mode for AF (you should have focus set to AF-C, and Release Priority) the shutter will release whether or not the body "thinks" focus is achieved.

    The indicator light becomes irrelevant once you recompose and/or enter Release Priority...
  7. interesting points, thanks guys
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