Technical Question - Focus "chatter"

[TMac99]

I have an R6 and I have noticed that when using Servo AF, occasionally, when actively focusing with Servo AF, even against stationary objects that should be easy focus targets, such as high contrast vertical lines, I hear the focus servos hunting (chattering). It seems worse on an STM lens, but is still there on a USM lens also (although the noise is much quieter). On the RF 50 1.8, I can even see the end of the lens moving in and out just a fraction. On my 24-240, I can see the movement of the focus distance in my on screen focus distance indicator. This occurs no matter what AF method I use (spot, Face tracking, Expanded etc). Is this normal, or do I have something wrong with my R6 body?

 

[MaraLee]

Do you have Continual AF turned on? I think it's on by default. Drove me CRAZY.

 

[TMac99]

Do you have Continual AF turned on? I think it's on by default. Drove me CRAZY.

No, I have that turned off, but of course, when using servo AF, it is essentially on for as long as I hold down the focus button, and that's when the chattering occurs.

 

[MaraLee]

I'm not much help, then. We have an old EF 70-200 f4 IS L lens of my husband's that I grabbed one day and was using with the hood turned backwards. It was doing like you're describing and I was ready to throw it. I finally figured out it was in the wrong IS mode, with the switch being hidden by the hood. I'd somehow bumped the switch or my husband had locked it on horizontal IS. One little setting can make such a huge problem, and I often immediately think something's broken.

 

[NickAndersonPhoto]

When I started I was quite disturbed by my EF lenses continually hunting when I wasn't trying to shoot! The chattering noise was alarming. I put it down to an aftermarket adapter and turned that setting off. Now, eventually, I have a Canon adapter but I leave that setting off. No idea why it was automatically on... perhaps there is someone who knows why?

 

[TMac99]

I have a Canon adapter but I leave that setting off.

Nick - what setting are you referencing here? Thanks

 

[NickAndersonPhoto]

Nick - what setting are you referencing here? Thanks

Sorry TMac... poor English! Leave the Continuous Focus setting off.

 

[TMac99]

Sorry TMac... poor English! Leave the Continuous Focus setting off.

I do not have Continuous Focus on. The chatter occurs when actively focusing in Servo AF. I use BBF, but I checked and I get the same chatter if I put focus back on the shutter button and just use a half shutter button press to focus. Basically any time I am actively using Servo AF I am likey to get the chatter.

Sounds like this is not happening to others, so my R6 body might have an issue

P.S. That just might be a first - an Englishman apologizing to an Aussie for using poor English

 

[TMac99]

After doing some troubleshooting with my friendly local camera store, we figured out that this is an "issue" when using Servo AF in lower light scenarios (I first found it in a typically lit room at night). It seems that the Servo AF can't quite decide that its focus point is good enough, so it keeps hunting. We tried this with a new R6 and saw the same behavior, so I am happy that it is just a "characteristic" and not a problem with my particular R6. This issue is likely a non-event, as it would be a rare case that you were needing Servo AF inside in lower light, and in any case, it seems that the camera still focuses OK, it just hunts around the right focus point.

One other characteristic I found, which likely most of you already know, is that the R6 can not focus against horizontal lines. If you try to focus on an area that only has horizontal lines, like a venetian blind, the focus has no idea what to do. This is most apparent if you are using "one point AF" or "Spot AF" since the field of view for the focus area is small and even if there are vertical lines in the entire frame, if the area the camera is using to focus does not have any verticality in it, it will not even come close to focusing. I think I knew this many many years ago, but I just figured with all the bells and whistles that the R6 focus system has, that they would have figured this out by now. The easy fix for this is to tilt the camera slightly, so that the horizontal lines now run a little diagonally, and that gives the focus system enough to use to focus.

 

[NickAndersonPhoto]

Nice bit of detective work Tracey. Not something I've seen in any reviews.