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VIP
Posts: 11,678
Registered: ‎12-07-2012

Re: T5i Autofocus Not Accurate

"I'm doing the same job with my T3i and my T5i under the same conditions."

 

If you have the lens adjusted to AF more accurately on the T5i, it will no longer do so on the T3i.

EOS 1DX and 1D Mk IV and several lenses!
Esteemed Contributor
Posts: 3,515
Registered: ‎02-17-2016

Re: T5i Autofocus Not Accurate

[ Edited ]

What? Are you sure about that Ernie? Why would the lens care?

Esteemed Contributor
Posts: 3,515
Registered: ‎02-17-2016

Re: T5i Autofocus Not Accurate

Sounds like the T5i is mis-adjusted and the AF sensor is a little closer to the lens preventing focus at the MFD.

 

Can you focus at the MFD in live view? The AF distance through the viewfinder may be slightly off.

New Contributor
Posts: 4
Registered: ‎09-14-2018

Re: T5i Autofocus Not Accurate


@kvbarkley wrote:

Sounds like the T5i is mis-adjusted and the AF sensor is a little closer to the lens preventing focus at the MFD.

 

Can you focus at the MFD in live view? The AF distance through the viewfinder may be slightly off.


Actually my guess is that the camera's sensor is a bit off of the focusing plane (is it possible?) because when focusing manually through the viewfinder also get slightly out-of-focuse pictures. As far as I know, AF system is located near the viewfinder, so it's apparently "seeing" the same I see. Have been focusing manually through live view since I realized about the problem and I got perfect pictures with that method. 

VIP
Posts: 11,678
Registered: ‎12-07-2012

Re: T5i Autofocus Not Accurate

"Are you sure about that Ernie? Why would the lens care?"

 

Of course I should have said it might not AF.  If a lens is adjusted precisely for a certain camera it may not do so for all cameras. All lenses have some tolerance built into the manufacturing process, so not every lens focuses exactly the same.

EOS 1DX and 1D Mk IV and several lenses!
VIP
Posts: 11,678
Registered: ‎12-07-2012

Re: T5i Autofocus Not Accurate

"...my guess is that the camera's sensor is a bit off of the focusing plane (is it possible?)"

 

Of course anything is possible but this is unlikely. The AF sensor has a mechanical adjustment, but the adjusting parts are glued after they are aligned at the factory by the tech. Fine adjustments are made with software.

EOS 1DX and 1D Mk IV and several lenses!
Esteemed Contributor
Posts: 3,515
Registered: ‎02-17-2016

Re: Autofocus Not Accurate

For the Rebel series this is strictly a last resort repair, it is not a common occurence. Usually the focus for any camera and lens is adequate.

 

Higher end cameras have AFMA which will allow for fine tuning.

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VIP
Posts: 8,645
Registered: ‎08-13-2015

Re: Autofocus Not Accurate


@mazenn wrote:

Mailing Canon your camera and lenses in cannot be much fun. Doing it again every time you buy a new lens seems like something that would make me reluctant to buy more lenses, which cannot be what Canon wants its customers to feel. 


The OP is using the wrong tool for a rather technical task.  Seeing how the point has been repeatedly ignored my inquiries about how exactly critical focus is achieved, I am convinced that operator is a major factor.  

 

Do I think the camera is back or front focusing?  Yeah, it could be, and it probably is.  But, that behavior is irrelevant when you are manually focusing the lens, which is what should be done to for most product photography.

It has been mentioned that Rebel camera bodies lack AFMA, auto focus micro adjustment.  Rebels do not need it.  The majority of Rebel users will use the camera kit lenses, which lack the ability to repeatedly focus in the same accurate way to make it worth the bother to try to implement AFMA with the kit lenses.  In other words, the kit lenses have too much focus slop to bother with AFMA..

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