Weird AF Issue on a6500
I've had a SPORADIC AF issue with my a6500 and my old a6300 (RIP). I've noticed it mostly with my SEL 10-18 f/4 OSS lens.
99% of the time AF is fine.
However, sometimes the camera will go completely out of focus for no APPARENT reason.
For instance, please look at these photos.
- Camera is on a tripod
- Using AF-S
- OSS / IBIS is turned off
- AF with shutter is turned OFF
- I am using a cable release to trigger the shutter
- Shots were taken about four seconds apart.
- Using back button focus to acquire focus.
- Single shot drive move.
So here's how I work. I use a cable release to trigger the shutter. I have AF with shutter turned off. I fist acquire focus with back button focusing. I take a shot with my flash (in my hand, using a flash trigger in the hot shoe) point at one wall, then another shot with it pointing at a different wall, and then another shot pointing at the ceiling.
99% of the time it is perfect.
But occasionally something like this happens; the focus just changes for no reason.
I am pretty darn certain that I didn't change the shots between photos.
I am also pretty darn certain that there is slack in the cable release so it is not a situation where I am accidentally jerking the camera around by the tethered cable release at the exact moment I am taking a photo. (Besides, it doesn't look like motion blur to me, but it could be.)
One other thing:
Sometimes when I take a series of shots with the a6500 and the 10-18 on a tripod, I notice that the framing is ever-so-slightly different. It's not like the tripod moved, but more like the focus point shifted SLIGHTLY and since the 10-18 is NOT a parafocal lens, there is a slight magnification / demagnification of the image.
Does this happen to other people?
Again, this happens when using AF-S, using back-button focus, and turning focus with shutter button to off.
thanks in advance.
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