# Autofocus problem



## goob4114 (Aug 20, 2015)

Hello all!

I have a Canon 1100D/T3 and I've been having problems with auto focus on all three of my lenses.  Unless the scene has a LOT of contrast, the auto focus just hunts forever focusing back and forth never locking in on anything.  This happens with every lens.  I don't know exactly how the focusing works, but my viewfinder looks pretty dirty (or I guess it could be the mirror that is dirty).  Could this be a possible cause?  If not, any ideas?


----------



## Woodsman (Aug 20, 2015)

Check your autofocus mode and AF point selection, page 81 and 82 of the manual.  On the back on the round cross key (the circular thing) press AF which is labelled on the side that faces right. The AF mode will then come up and you can change it with the main dial wheel.  Try going to one shot mode (best for still subject). 

Then on the back the top right button that looks like a cross inside a box (the one to the right of the * key) is the AF point selection button. Press that. Use the wheel to move from automatic to manual selection and continue using the main dial wheel to select a single focus point.  For example the one in the middle is active.  

Test it this way asd you have told the camera to focus only on the centre point each time, and not try to decide what it should focus on.   It should focus fast and accurately on the centre of the screen.  If it doesnt then you may have a problem that needs service. If it does focus then play with the settings of the AF mode to find the mode that works best for you


----------



## Derrel (Aug 20, 2015)

Here is an article about autofocus troubleshooting. Autofocus troubleshooting by Thom Hogan

It's written from the POV of Nikon, but the AF system most cameras use is similar, with the AF sensors located inside the camera, at the bottom of the mirrorbox sub-assembly; the AF sensor module is visible only when the mirror has swung UP, and is being held in the UP position by using the B-mode exposure time with the shutter release depressed continually, or a long exposure time such as 30 seconds, or in the special sensor cleaning mirror-up mode that some camera models have. Your camera ***might*** have a small fiber or something trapped in the AF module area; this could be a very,very small fiber, such as one from a sweater or pet, etc.. It is certainly worth checking into this possibility.


----------



## goob4114 (Aug 20, 2015)

Woodsman said:


> Check your autofocus mode and AF point selection, page 81 and 82 of the manual.  On the back on the round cross key (the circular thing) press AF which is labelled on the side that faces right. The AF mode will then come up and you can change it with the main dial wheel.  Try going to one shot mode (best for still subject).
> 
> Then on the back the top right button that looks like a cross inside a box (the one to the right of the * key) is the AF point selection button. Press that. Use the wheel to move from automatic to manual selection and continue using the main dial wheel to select a single focus point.  For example the one in the middle is active.
> 
> Test it this way asd you have told the camera to focus only on the centre point each time, and not try to decide what it should focus on.   It should focus fast and accurately on the centre of the screen.  If it doesnt then you may have a problem that needs service. If it does focus then play with the settings of the AF mode to find the mode that works best for you



Thanks for the response, but I know it's not any of these.  I've had the camera for close to 3 years, and it just started having this problem in the last week or two.  It doesn't matter what mode its on or which focus points are enabled; the behavior is the same.


----------



## goob4114 (Aug 20, 2015)

Derrel said:


> Here is an article about autofocus troubleshooting. Autofocus troubleshooting by Thom Hogan
> 
> It's written from the POV of Nikon, but the AF system most cameras use is similar, with the AF sensors located inside the camera, at the bottom of the mirrorbox sub-assembly; the AF sensor module is visible only when the mirror has swung UP, and is being held in the UP position by using the B-mode exposure time with the shutter release depressed continually, or a long exposure time such as 30 seconds, or in the special sensor cleaning mirror-up mode that some camera models have. Your camera ***might*** have a small fiber or something trapped in the AF module area; this could be a very,very small fiber, such as one from a sweater or pet, etc.. It is certainly worth checking into this possibility.



Thanks.  I'll give this a shot tomorrow evening and let you know how it goes.


----------



## goob4114 (Aug 22, 2015)

Derrel said:


> Your camera ***might*** have a small fiber or something trapped in the AF module area; this could be a very,very small fiber, such as one from a sweater or pet, etc.. It is certainly worth checking into this possibility.



I locked up the mirror for "manual cleaning", blew a couple of times with canned air, and it vastly improved the auto focus.  It doesn't seem to be quite back to where it was (but that could just be my mind playing tricks), but it is without a doubt way better.  Thank you!


----------



## Derrel (Aug 22, 2015)

goob4114 said:


> Derrel said:
> 
> 
> > Your camera ***might*** have a small fiber or something trapped in the AF module area; this could be a very,very small fiber, such as one from a sweater or pet, etc.. It is certainly worth checking into this possibility.
> ...



Good to hear this! Thanks for posting a follow-up on your situation.


----------

