D780 and Z owners - AF-C Single Focus - LiveView vs OVF any different?

Started 3 months ago | Discussions thread
ericbowles
ericbowles Senior Member • Posts: 1,337
Re: D780 and Z owners - AF-C Single Focus - LiveView vs OVF any different?
4

skyrunr wrote:

Q. Does the AF-C and Single focusing area using the OVF (versus LiveView) continue to no settle (nervous/jitter/search) or does it behave more like a DSLR?

The big difference between On-Sensor Focus and other approaches seems to be the handling of severely out of focus scenes.

With a DSLR, the focus sensor is at the bottom of the mirror box.  The camera focuses with a lens wide open.  The lens hunts if it lacks a contrasty target under or near the AF sensor selected.

With On Sensor AF, you only have horizontal sensors - there are no cross sensors.  They actually dedicate rows of photosites on the sensor for focus.

If the camera does not know where to focus, it either hunts - racks from one end to the other possibly multiple times, or it gives up.  In these cases not only is focus not fast, but you may never achieve focus.

You need some contrast to focus, and a fast lens or a long lens is more likely to have DOF that has a portion of a scene completely out of focus.  The trick is to prefocus at a distance where you have more contrast.

The other issue you run into is jitter.  When I have jitter, it's because my subject is small and I am struggling to focus on the correct distance.  The AF sensor is hovering between two potential targets at different distances.  The Z cameras are more accurate than a DSLR, so with a fast lens you could run into this issue.  You might also encounter it with lines that are parallel to the sensor, and the lack of cross sensors makes a difference.

If Single point is moving around, something odd is happening.  Single point AF should never move from where it was placed.

So the focus issues you are describing are at least in part a matter of technique.  It sounds like you are trying to use a DSLR focus system with a on-sensor focus.  They are different, so you need to learn to use on-sensor focus.  The benefit is focus is going to be more accurate.

Suggestions:

  • Prefocus near the right distance
  • Be clear about your AF target - pick a good target
  • Change AF modes if needed
  • Manually adjust focus if the camera does not immediately focus on the target - it holds focus pretty well
  • Pick a target that is around the size of your AF sensor or larger
  • Use VR - or a monopod or tripod if you can't maintain the AF sensor on your target - the viewfinder stabilizes
-- hide signature --
 ericbowles's gear list:ericbowles's gear list
Nikon 1 V1 Nikon D800E Nikon D850 Nikon Z6 Nikon Z50 +27 more
Post (hide subjects) Posted by
Keyboard shortcuts:
FForum PPrevious NNext WNext unread UUpvote SSubscribe RReply QQuote BBookmark MMy threads
Color scheme? Blue / Yellow