AFc - vibration + buzzing despite constant distance to subject

[Macberg]

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Hi there,

 

I have been a proud owner of the Leica Q for three days now - at the moment I am working myself through all the technical possibilities of this beautiful camera. One issue got my attention:

 

Whenever I set the autofocus in the menu to AFc (shutter release priority, mid-size focus-field) and focus on an object, the autofocus keeps moving constantly, the display picture seems to tremble (focus point seems to "vibrate" back and forth within a certain scope) and you can hear a constant buzz for as along as I keep pressing the shutter release button halfway down.

 

Obviously the camera keeps repositioning the autofocus (which I guess it is supposed to do), but in this case it does that even if the distance between camera and subject doesn't change at all, e.g. if I put the camera on the table and the focused subject doesn't move (standing on the same table).

 

Is that normal? Have you observed that behaviour on your Leica Q, too?

 

The firmware of my Q is 2.0.

 

Thanks a lot for your answers.

[Bart van Hofwegen]

The Q, for the lack of phase detection, uses contrast auto focus. Cameras with phase detection "know" when something is in focus when the two beams of light are synced in phase. Contrast AF cameras have no way of knowing if a certain high edge contrast situation cannot actually be improved further. That means that the Q changes focus until until it finds the greatest edge contrast in the designated area. When set to continuous, it must keep doing this for there is no information about subject distance, as in phase detection AF. It must constantly try to achieve greater contrast to keep the "promise" of best possible focus. So yes, this is normal and I am seeing this in other cameras also.

 

BTW: As far as I know, when in AFc, the camera is always in shutter release priority, but this can be a good thing, considering that AFc is meant for moving targets. With cameras that offer focus prio, I often find that shutter release prio does a better job, especially for faster moving targets.

[Macberg]

OK, thank you for the information. I will try and get used to it...

[AndyyEpp]

I noticed this behaviour of the Q as well and it was disturbing me with it's constant noise and vibrating. I recently had that explained to a Leica technician and he didn't have a clue for it But I think you got the answer from Bart already.

 

Actually I for myself never really use and need the Q in AFc mode with that camera. 

[viramati]

It is normal behaviour in AFc mode