t5i couldn't focus Occasionally

There are some instances that my camera would not focus. I have to turn it off then on again and sometimes I miss the shot. The scene would be well lit so I dont think light is a problem.

I am using it with a Tamron 17-50mm 2.8 non VC.

I am not sure if there is a problem with the camera or the lens. I cannot reproduce the malfunction on demand.

any ideas?

Does it ever happen with a different lens? Seems like knowing that would narrow it down to a lens or camera problem (I'm guessing it's a lens problem, but that's just a hunch).

groundloop wrote in post #16752091
Does it ever happen with a different lens? Seems like knowing that would narrow it down to a lens or camera problem (I'm guessing it's a lens problem, but that's just a hunch).

i have a 50mm 1.8 that focuses well. I can't be so sure tho because I don't know how to repeat the problem...

The lens is not being switched to manual focus in error, is it?

Frodge wrote in post #16752108
The lens is not being switched to manual focus in error, is it?

No, I make sure its always on AF

Often it's the "Lens drive when AF is impossible" setting that's set to OFF. It creates exactly the symptom you describe, if you don't know when to use it and when not to.

Trying to focus extremely closely, inside the lenses designed range, can do it.

In combination with the "Lens drive with AF impossible" being set to OFF, yes. Otherwise, the camera will send the lens for a focus hunt.

Of course, if you are aiming at something without any useful contrast, like a blue sky, you get the same thing.

That's the first thing that I thought of too...Great minds think alike.

Unfortunately the T5i doesn't have that custom function. Lens drive when AF is impossible is therefore always on.

We need more information.

OP, does the lens hunt or just refuse to move at all? How close is your subject? Does this happen only with plain, single color, or non-contrasty subjects?

the lens does not hunt at all. it doesn't move. There is also the absence of the red light in the focus points as if the lens is in Manual focus mode.

the subject is not too close or non contrasty. I can get a picture of the same subject after i turn off and then on the camera in the same distance. Sometimes turning it on and off multiple times for the focus to resume.

hope that helps...

thank you all for the responses!

At this point I would try a couple different lenses to see if the problem persists.