FS5: Focus "hunting" - bug or defective unit?

W

WallaceLau

New member
[EDIT: Sample video link HERE.]

Howdy! First post here and nice to meet everyone!

I've been renting FS700 in the past and when the FS5 came out we took the plunge and bought one. Figure it will pay for itself in a couple years.

However after the first outing I noticed there is focusing problem that I've never seen on the FS700. It is extremely noticeable in super slow-motion footage. The best way I can explain it, is that during focusing it will go "two-step forward, one-step back" until the scene is in-focus. Then it will go "one step forward, one step back" the whole time. Long story short, auto-focus footage is completely unusable.

I've done a lot of searching and can't find any mention of similar issue on any forum, so I figure I might have a defective unit? Anyone heard of something similar?

I will try to share some actual footage later.

Thanks in advance for any comments!



Wallace
 
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Oh by the way it is happening on both the kit lens (18-105 F4G) and an old 18-200 PZ, so I am leaning towards the problem is with the camera...
 
Sounds like you have Face Detection on. I noticed with it on---yeah, it works, but in an interview it constantly is doing micro adjustments (like it's supposed to) but with a background visible behind the talent---it shows going soft to sharp several times. I wanted to try it out---never again.
 
Steve Harryman said:
Sounds like you have Face Detection on. I noticed with it on---yeah, it works, but in an interview it constantly is doing micro adjustments (like it's supposed to) but with a background visible behind the talent---it shows going soft to sharp several times. I wanted to try it out---never again.
Click to expand...

I am fairly certain face detection is off, since the quick-adjust button (F5 I think) does NOT work with face detection on. And there is no green square on the LCD to indicate who's face the camera is tracking...
 
Here is a link to a file straight out of the camera: DropBox

File size is 434MB. The moving subject started in-focus, and as I pan the camera to follow, the subject becomes out of focus. You can see the camera tries to regain focus but during so it steps in-and-out constantly, like a pulse.

For those who also owns an FS5, is there any chance you can confirm if your unit will do the same? I can recreate this any time the camera is focusing, so all you have to do is put a foreground subject in the frame, turn on auto-focus, start Super-SlowMo recording, and remove the foreground subject. On my unit, when the camera re-focus to whatever is on the background, it will do this back-and-forth thing until it has focus lock. And once it has focus lock, it will still "hunt" back-and-forth so the scene is constantly in-and-out of focus, even though nothing moves and the camera is on a tripod.

Thanks!!!



Wallace
 
Yeah, I saw the same thing during my initial tests. Constant jittering especially visible in out of focus areas behind interviewees! My FS700 and FS100 before that were the same. I wish this camera had the DPAF technology of the A6000, that camera focuses like magic.
 
AlexLeith said:
Yeah, I saw the same thing during my initial tests. Constant jittering especially visible in out of focus areas behind interviewees! My FS700 and FS100 before that were the same. I wish this camera had the DPAF technology of the A6000, that camera focuses like magic.
Click to expand...

I don't recall ever seeing the same problem with the FS700... especially when the camera clearly know where it needs to focus. I've been wondering if the subject line of my topic was misleading; it's not "focus hunting" in the traditional sense (that after the subject is in-focus, the camera can't make up it's mind and keep going back-and-forth). This happens when the camera clearly know the subject is too far or too close from the current focal point, but it acts very strangely "getting there".

Let me see if I can explain this again... let's say there are "only" 10 focus steps, step 1 being the lens' minimum focus distance, and 10 is infinity. Say I have a subject fairly close to the camera (at distance "4") while there is a mountain as backdrop (focus distance "10"). If the camera is focused on my subject, and the subject suddenly walked off the frame, most camera would go from 4 to 5-6-7-8-9 and finally 10 - in a very linear fashion. If the subject walks back into the frame, the camera would usually wait a little bit and then focus back from 10 to 9, 8, 7, 6, 5, and stop at 4. Sometimes it overshot the focus and went to 3, and have to go back from 3 to 4. Which is what we commonly know as focus hunting. But that's NOT what my problem is.

In my case, if my subject walks off the frame, the FS5 would act like this: 4-5-6-5-6-7-6-7-8-7-8-9-8-9-10-9-10-9-10... refocusing from the subject to the mountain is NOT liner. In almost 30 years of shooting (from film to digital to video), I've never once seen a camera/lens does that. And it's extremely predictable and repeatable.

I hope I am not doing something stupid to have caused this behavior, but I am going to return my current unit and order a replacement... if the replacement does the same thing, I would have to seriously think about keeping the FS5. =(

Thanks,



Wallace
 
Dont rely on Auto Focus unless you have a deep depth of field then you can get away with it.

As your noticing its too unreliable. And of course in slow motion every little focus hunt is going to show up (which btw is not specific to the FS5)

Nothing too unusual about yr clip, you have a lot of guys running how would the camera know which one u want to focus on? Go manual, use peaking your shot is not too shallow so you would have got a better result :)
 
Not sure why anyone would want to engage auto focus in a relatively static managed scene, or auto anything. If you are looking to grab that headline shot in a media scrum, fine, but other times letting the camera make decisions for you is often asking for problems.
 
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