T7i won't focus

[daximus]

My T7i has started to jump around when focusing.  At first it was quick to focus, but now when focusing it jumps back and forth and never focuses.  Is this a camera problem or lens problem?

[SamanthaW]

Hi there, thanks for posting! 

One thing that might help the community narrow that down, is trying a second lens on your T7i. If the issue is the same, it's probably something with the camera, if the issue goes away, it might be the lens! 

[daximus]

I tried that, but the only other lens I have is tiny compared to the one I use all the time.  It does jump a bit, but not like the large one.

[Tronhard]

Hi and welcome to the forum.

To assist us it would be helpful to know what lens you are using.

[daximus]

I’m using an old Sigma 150-500

[Tronhard]

Have you tried another lens and if so, how does that behave?

Also, please check the AF selection switch on the Sigma 150-500: what settings are selected please?

If the focus limiter switch is not set to FULL, but is set at one of the other, particularly 10m to infinity (sideways 8), it is possible that the lens is not configured for the distance at which you are focusing.

[John_Q]

Hello daximus,

You may want to try cleaning the contacts on the camera and lens especially, with a clean, dry, microfiber cloth to ensure good communication between them. Prior to testing, I would also suggest removing any lens filter that may be attached to the front of the lens since certain lens filters may sometimes interfere with the camera's auto focusing system. You may try a different lens on the camera if the issue persists. This will help determine if it's a camera or lens issue. These cameras do operate with a 2-step shutter process where you press the shutter button half-way to focus and once focused, you continue to press the shutter in completely to take the shot. When pressed half-way, you should get a red dot to blink inside the AF point achieving focus, a beep will sound and the focus indicator in the bottom right corner of the viewfinder will light up. We would recommend testing this in a well-lit environment or possibly outside during the daytime when there is a lot of light available.