T5i Autofocus Not Accurate

[avimoore]

Hi, a little while ago I bought a new Rebel T5i from Best Buy with money recieved from a warrantied T2i. I havent been using the T5i as much as I used to use my T2i, so it took a little while to notice this issue. It seems that the autofocus on my T5i is not focusing on what it intends to. It seems to be truely in focus a little behind what the camera will beep saying is in focus. It is especially noticeable with my 50mm f1.8  with a narrow depth of field. I use single point autofocus and the camera will say it is focused on a certain point in the frame, but then the picture will always be slightly out of focus, with whatever is slightly behind the subject looking a bit sharper. Anybody else have this problem? I can take some test shots and upload them too. It makes all pictures slightly off with every lens, so it also exagerates finging and abberation and blurriness that I didnt have when using the same lenses on my T2i.

[ebiggs1]

"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.

[kvbarkley]

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

[ebiggs1]

"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.

[kvbarkley]

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.

[damianwasser]

---

@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. 

[ebiggs1]

"...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.

[kvbarkley]

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.

[Waddizzle]

---

@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..