# Canon T3i auto focus problem



## gbmono (Jul 23, 2014)

Hello

I have the Canon T3i and love it the only problem is that the auto focus in the viewfinder does not work. It works fine in Live-View but in the viewfinder it just tracks back and fourth in between macro and infinity it happens on all of my lenses and I have already re set to default and wiped the card and cleaned the contacts.

Please Help ASAP 
-- thanks, griffin


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## JacaRanda (Jul 23, 2014)

Is this happening in a low light area?  Make sure you have plenty of light.


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## Derrel (Jul 23, 2014)

Not sure if I understand correctly, but is it perhaps set to an automatic AF area selection mode?


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## Big Mike (Jul 24, 2014)

Can you describe your situation with more detail?

When the AF is 'hunting' like that, it's usually due to a lack of contrast.  Usually that is because you're trying to shoot in rather low light.


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## ronlane (Jul 24, 2014)

Big Mike said:


> Can you describe your situation with more detail?
> 
> When the AF is 'hunting' like that, it's usually due to a lack of contrast.  Usually that is because you're trying to shoot in rather low light.



I have on occasions switched to AI Focus or AI Servo mode and forgot to change it back, then have issues focusing with the AF "hunting" like that. Might double check to make sure you are on One Shot.


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## gbmono (Jul 24, 2014)

Big Mike said:


> Can you describe your situation with more detail?
> 
> When the AF is 'hunting' like that, it's usually due to a lack of contrast.  Usually that is because you're trying to shoot in rather low light.



It happens everywhere even in in braud daylight, keep in mind that AF works perfectly in Live View


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## TCampbell (Jul 24, 2014)

There are 9 AF points on your camera.  Are you in auto-select mode (camera can choose any AF point) or are you picking a specific AF point.

There may be something blocking the light path to the AF sensor array.  You may want to tell your camera you want to manually clean the sensor so that it flips the mirror up and allows you to inspect the inside.  Make sure nothing is blocking the AF array (it's on the floor of the camera) and also check the underside (backside) of the reflex mirror.  There's a semi-silvered section which allows some light to pass down into the AF sensors when the mirror is in the "down" position.


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## gbmono (Jul 24, 2014)

TCampbell said:


> There are 9 AF points on your camera.  Are you in auto-select mode (camera can choose any AF point) or are you picking a specific AF point.
> 
> There may be something blocking the light path to the AF sensor array.  You may want to tell your camera you want to manually clean the sensor so that it flips the mirror up and allows you to inspect the inside.  Make sure nothing is blocking the AF array (it's on the floor of the camera) and also check the underside (backside) of the reflex mirror.  There's a semi-silvered section which allows some light to pass down into the AF sensors when the mirror is in the "down" position.



I tried all of it by using some compressed air and gentley blowing in that area and nothing helped


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