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Archive 2015 · Sudden autofocus problem on 5D Mark III

  
 
sdhweb
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p.1 #1 · p.1 #1 · Sudden autofocus problem on 5D Mark III




Hello, I have a nearly two years old 5D Mark III with only 7800 images taken. The camera has been working well and I've been happy until now.

Yesterday I experienced that autofocus would not work on an easy target. I thought 'what the heck is going on?'... After that incident I keep having this problem. Sometimes autofocus seems to work and sometimes it seems to do nothing at all. The focus confirmation light and the AF status indicator is just flashing.

I use the AF-ON button for focus and the IS is leaping to action but the autofocus doesn't seem to be doing anything. I experience this on contrasty subjects in full daylight. And suddenly it may be working again but it seems very unstable. I haven't done any changes to the settings before this started to happen.

It seems to be worse when I change back and forth between focusing on something close and something far away. If I manually adjust the lense very much out of focus it seems to have a very hard time to get back on track. Mostly it fails. If I then help it quite a bit and manually adjust the lense more in focus it suddenly works again.

I've always had the setting 'Lense drive when AF impossible' set to OFF and I've never had these problems before. Changing this setting to ON seems to 'help' a little, it at least changes the behaviour of the autofocus. With this enabled in seems to at least be trying (and more often succeed) instead of just doing nothing. Keep in mind that I'm talking about good and easy autofocusing conditions here, not low light situations.

Conciderations:

1. I have tried two different lenses with the same result (EF 70-200 F4L IS USM and the EF 100 F2,8L IS macro)

2. I have cleaned the lense contacts on both the body and the lense.

3. I've upgraded from firmware 1.2.3 to 1.3.3 and reset the camera to factory settings.

4. I've changed focus back to the shutter button

5. This happens in both One shot and AI-servo modes (probably AI focus as well but not tested).

6. I've always used the center focus point alone

None of the above actions have made any difference to the situation. I've had this camera for nearly two years and something has definitely happened. The camera is very well treated and have no visible damages.

Any advice on this one?



Jul 14, 2015 at 02:37 AM
atwl77
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p.1 #2 · p.1 #2 · Sudden autofocus problem on 5D Mark III


Is there a possibility of something (dust, lint, etc) partially obstructing the AF sensors? Try using a rocket blower on it to see if it makes any difference?


Jul 14, 2015 at 02:47 AM
Ian.Dobinson
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p.1 #3 · p.1 #3 · Sudden autofocus problem on 5D Mark III


atwl77 wrote:
Is there a possibility of something (dust, lint, etc) partially obstructing the AF sensors? Try using a rocket blower on it to see if it makes any difference?


+1

By the way the AF sensor is in the BOTTOM of the body .
other causes could be a dirty mirror (main mirror or the sub mirror behind ) . if it is dirty then be careful its not recommended to clean yourself.
or the worst case could be that the sub mirror has moved and isnt directing the light path properly .




Jul 14, 2015 at 05:22 AM
Paul Mo
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p.1 #4 · p.1 #4 · Sudden autofocus problem on 5D Mark III


sdhweb wrote:
Hello, I have a nearly two years old 5D Mark III with only 7800 images taken.

Any advice on this one?


Yes. Take more photos.



Jul 14, 2015 at 05:44 AM
schlotz
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p.1 #5 · p.1 #5 · Sudden autofocus problem on 5D Mark III


How about an actual sample of one, showing where the AF target point was?


Jul 14, 2015 at 10:10 AM
Shutterbug2006
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p.1 #6 · p.1 #6 · Sudden autofocus problem on 5D Mark III


Reset your camera to factory defaults and try again.

Welcome to FM.



Jul 14, 2015 at 10:13 AM
sdhweb
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p.1 #7 · p.1 #7 · Sudden autofocus problem on 5D Mark III


Hi,

Thanks for the response. I've tried to clean it by using a blower with the mirror up, but it looks very clean inside. After the cleaning I took about 1000-1500 images, mostly of flying seagulls and thought the autofocus was OK. But right before it was time to go home it failed again. I had just focused on a stone 2 meters away, and then when I tried to focus on the mountains in a distance it just fails. It cannot focus. There is plenty of light and contrast.

I have done the same test several times during todays testing and it worked every time so I really thought the cleaning did the job. But failure again right before I was going home :-(

So I guess I need to send it in for repairs...



Jul 14, 2015 at 01:16 PM
sdhweb
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p.1 #8 · p.1 #8 · Sudden autofocus problem on 5D Mark III


Shutterbug2006 wrote:
Reset your camera to factory defaults and try again.

Welcome to FM.


Thanks, already tried as you can see in # 3 :-)



Jul 14, 2015 at 01:16 PM
sdhweb
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p.1 #9 · p.1 #9 · Sudden autofocus problem on 5D Mark III


schlotz wrote:
How about an actual sample of one, showing where the AF target point was?


I don't shoot when it's very obvious that the picture is very much out of focus. The problem is that it cannot find focus when it really should be able to. The problem is not that it misses focus when I do shoot.



Jul 14, 2015 at 01:18 PM
sdhweb
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p.1 #10 · p.1 #10 · Sudden autofocus problem on 5D Mark III


Paul Mo wrote:
Yes. Take more photos.


Almost 10.000 now ;-)



Jul 14, 2015 at 01:19 PM
msalvetti
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p.1 #11 · p.1 #11 · Sudden autofocus problem on 5D Mark III


Based on how long you've been wrestling with this and the fact it happens with more than one lens, I doubt your problem is the focus limiter switch on the lens, but maybe something to double-check. If the lens is focused on something near and the focus limiter switch is set to farther out, I think the camera will behave as you described.

I've had more panics than I'm willing to admit that were due to the switch position. Next time you have the problem, maybe try moving the switch back and forth.

Mark



Jul 14, 2015 at 01:45 PM
sdhweb
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p.1 #12 · p.1 #12 · Sudden autofocus problem on 5D Mark III


msalvetti wrote:
Based on how long you've been wrestling with this and the fact it happens with more than one lens, I doubt your problem is the focus limiter switch on the lens, but maybe something to double-check. If the lens is focused on something near and the focus limiter switch is set to farther out, I think the camera will behave as you described.

I've had more panics than I'm willing to admit that were due to the switch position. Next time you have the problem, maybe try moving the switch back and forth.

Mark


Thanks for the tip Mark but the problem occurs just as much in the 'far' end.



Jul 14, 2015 at 01:48 PM
rattlebonez
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p.1 #13 · p.1 #13 · Sudden autofocus problem on 5D Mark III


check the 1st and 2nd focus priority is set for "focus"
if that fails try reset to factory defaults



Jul 14, 2015 at 02:06 PM
snapsy
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p.1 #14 · p.1 #14 · Sudden autofocus problem on 5D Mark III


sdhweb wrote:
Hi,

Thanks for the response. I've tried to clean it by using a blower with the mirror up, but it looks very clean inside. After the cleaning I took about 1000-1500 images, mostly of flying seagulls and thought the autofocus was OK. But right before it was time to go home it failed again. I had just focused on a stone 2 meters away, and then when I tried to focus on the mountains in a distance it just fails. It cannot focus. There is plenty of light and contrast.

I have done the same test several times during todays testing and
...Show more

You can distinguish between a AF sensor issue vs an AF motor/drive issue by switching to MF, entering LV, manually focus at maximum magnification, then exit LV (staying in MF mode) and half-press the shutter and see if you get an AF confirmation. If you get the AF confirmation that means the AF sensors are working ok and it's a motor/drive issue; if you don't get a confirmation that means it's the AF sensors (either malfunctioning or obstructed).



Jul 14, 2015 at 02:12 PM
dhachey
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p.1 #15 · p.1 #15 · Sudden autofocus problem on 5D Mark III


+1, Solved this problem for me a couple of times. Does it AF in live view? If so, then check for dust bunnies on the AF sensor. Just low it out with a rocket blower. Do not use compressed air, it contains oil aerosols that will make matters worse.

atwl77 wrote:
Is there a possibility of something (dust, lint, etc) partially obstructing the AF sensors? Try using a rocket blower on it to see if it makes any difference?




Jul 14, 2015 at 07:41 PM
sdhweb
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p.1 #16 · p.1 #16 · Sudden autofocus problem on 5D Mark III


snapsy wrote:
You can distinguish between a AF sensor issue vs an AF motor/drive issue by switching to MF, entering LV, manually focus at maximum magnification, then exit LV (staying in MF mode) and half-press the shutter and see if you get an AF confirmation. If you get the AF confirmation that means the AF sensors are working ok and it's a motor/drive issue; if you don't get a confirmation that means it's the AF sensors (either malfunctioning or obstructed).


When you say motor/drive issues, I assume you are talking about lenses? I doubt that 3 of my lenses have the same problem. One of them is nearly brand new. AF is working, sometimes. And other times it cannot find focus when it really should be able to. It's a very weird behavior if you ask me. I've tried using a blower.



Jul 15, 2015 at 03:01 AM
dhachey
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p.1 #17 · p.1 #17 · Sudden autofocus problem on 5D Mark III


Looks like a trip to Canon is in order. Sorry.


Jul 15, 2015 at 04:26 AM
snapsy
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p.1 #18 · p.1 #18 · Sudden autofocus problem on 5D Mark III


sdhweb wrote:
When you say motor/drive issues, I assume you are talking about lenses? I doubt that 3 of my lenses have the same problem. One of them is nearly brand new. AF is working, sometimes. And other times it cannot find focus when it really should be able to. It's a very weird behavior if you ask me. I've tried using a blower.

Motor/drive includes the mount communication between the camera and lens, where the camera is commanding the lens to move. AF involves sensing and moving operations - if you run the experiment I described you'll see which of those two general areas the problem is in. You can have a scenario where the sensing is fine (AF sensors working) but there be something wrong with the mount communication that causes AF driving to fail on all lenses, including signaling problems or power problems.



Jul 15, 2015 at 05:10 AM
RCicala
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p.1 #19 · p.1 #19 · Sudden autofocus problem on 5D Mark III


If there's not dust or lint over the AF sensor (most common cause) then sounds like the AF sensor has gotten shifted out of it's calibrated position. Has to go to Canon to be recalibrated.


Jul 16, 2015 at 05:40 AM
sdhweb
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p.1 #20 · p.1 #20 · Sudden autofocus problem on 5D Mark III


Hi all, I'm sorry for the late reply here. It took the shop over 4 weeks from they received the camera till they actually started working on it. They blamed it on summer vacation ;-)

It only took them a day to repair though once started. RCicala is right. The AF-sensor had gotten shifted out of it's calibrated position (no clue how that happened) and it had to be recalibrated and then the AF had to be adjusted. They said the camera needs to be impacted for the sensor to 'move'. I don't know how this may have happened since I'm very careful with my gear, but I'm glad the problem is fixed :-) Thanks



Aug 30, 2015 at 02:15 PM
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