XT20 pre-af in auto mode

[parastratos]

I just mounted a fujinon 27mm lens to my xt20 and I noticed that it makes a constant sound because it keeps trying to auto focus.

My 16-50 lens didn't have the same behavior.

I have disabled the pre-af option in non-auto mode but I don't have access to this option in auto mode.

I upgraded the body's firmware but didn't see any difference...

So I have some questions:

Is this normal for a lens to have this behavior?

Can I somehow disable the pre-af on auto mode?

[Doug Pardee]

Select any Auto scene mode other than SR+ -- use Portrait, Portrait Enhancer, Landscape, Sport, etc.

SR+ (automated scene recognition) needs to continuously scan to determine what kind of scene the camera is pointed at now. That includes varying the focus. If you leave the camera pointed at a scene for a few seconds, SR+ should settle down. As soon as you point somewhere else, or something in the scene changes, it'll start back up again.

If you select a specific scene mode, there's no need for all of that scanning.

SR+ is a battery hog, and if you're going to use Auto, I definitely recommend selecting an appropriate scene mode whenever you can.

Oh, and the lens difference is just that the 27mm focuses by moving the entire optical assembly back and forth, which is slow and noisy... but retains excellent IQ given the restrictions of the pancake form factor. You'll see similar behavior on the Fuji primes that are faster than f/2. The 16-50 was doing the same thing, but with its lightweight inner-focusing system it's only obvious if you're looking through the viewfinder.

Edited July 14, 2019 by Doug Pardee
Added discussion of lens difference

[parastratos]

Thanks a lot, this was really helpful.