Having Trouble with Autofocus

Started Mar 19, 2022 | Discussions thread
PHXAZCRAIG
PHXAZCRAIG Forum Pro • Posts: 20,425
Re: Having Trouble with Autofocus

Well, for typical back button focus, you have the wrong settings.

You want it to focus and take a picture when you a) press your back button to focus and then b) press shutter release.

That sounds obvious, but it leaves out the part where the camera decides when it is in focus.  It simply takes a shot when you press that shutter release.  The part where you press the back button to focus also needs to include your own judgement that focus has been achieved - even if you focus-and-recompose.

Your settings - AF-s, is a problem for the above.  It should be AF-c, for continuous focus.   That gives it maximum flexibility - you want to focus on a moving object?  Just keep back button pressed.  Want to focus and recompose?  Focus, then lift thumb.

In order for the camera to take a shot whether it thinks things are in focus or not you must set the camera to release priority.  (Release+focus ok too, but I think it's only supposed to help when shooting at a high frame rate.)  There are two distinct uses for this setting.  One is to allow you to focus, then recompose and shoot even though the focus point is no longer on the subject.  The other is to grab a shot either quicker than the camera determined focus was achieved or simply take shot when it isn't possible for the camera to even tell about - this includes shooting black subjects and sometimes foggy ones - low contrast conditions.

In addition, the camera will be more sensitive to vertical lines than horizontal ones in most situations.

With your camera set to AF-S and focus priority, it will not take a shot if it doesn't think focus has been achieved.  This includes focusing and then recomposing (camera will try to refocus).  Problematic subjects cause issues.  I ran into it years ago with a D300 struggling to maintain focus on a squirming black puppy.

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Phoenix Arizona Craig
www.cjcphoto.net
"I miss the days when I was nostalgic."

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