Weird AF Issue on a6500

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Off The Mark Senior Member • Posts: 1,654
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.

Everything is fine in this first photo.

Second photo taken a few seconds after the first. Still looking good?

Holy Schnikes!!! What happened here??? Taken only four seconds after the previous (in focus) photo.

- 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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Sony a6000 Nikon D750 Sony a6500 Sony 85mm F2.8 SAM Tamron SP 70-300mm F/4-5.6 Di VC USD +5 more
Sony a6300 Sony a6500
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