50mm 1.8 STM Won't Switch to AF When Mounted

[nullgate]

I just purchased a new 50mm 1.8 STM today. I mounted it and it was already in AF mode. I took a few shots. Focused perfectly.

Then I switched to MF focus and took some shots. Still no issue.

When I switched back to AF, I noticed that it wasn't focusing. Sure enough, my T5i still said that I was in MF mode. I turned off the camera, and turned it back on without changing the focus mode on the lens. Still stuck in MF mode. The physical switch worked normally and there was no odd movement to it.

I unmounted to lens, examined the pins on the body and the contact points on the lens. Both seem fine. I remount the lens, and while still in AF, turn on the camera. It's now back in AF mode.

Other things I've tried since then:

- Updating the firmware of my T5i to the latest firmware

- Removing the battery, lens, memory card from the camera and leaving it off for several minutes

- Switching to another lens and trying out the AF/MF switch, and it works perfectly on my other lenses

Anyone else have any ideas, or should I be looking to return this lens or find a Canon repair shop to fix it?

I'm assuming it would be under manufactor warranty on day 1.

[Tronhard]

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@nullgate wrote:

I just purchased a new 50mm 1.8 STM today. I mounted it and it was already in AF mode. I took a few shots. Focused perfectly.

Then I switched to MF focus and took some shots. Still no issue.

When I switched back to AF, I noticed that it wasn't focusing. Sure enough, my T5i still said that I was in MF mode. I turned off the camera, and turned it back on without changing the focus mode on the lens. Still stuck in MF mode. The physical switch worked normally and there was no odd movement to it.

I unmounted to lens, examined the pins on the body and the contact points on the lens. Both seem fine. I remount the lens, and while still in AF, turn on the camera. It's now back in AF mode.

Other things I've tried since then:

- Updating the firmware of my T5i to the latest firmware

- Removing the battery, lens, memory card from the camera and leaving it off for several minutes

- Switching to another lens and trying out the AF/MF switch, and it works perfectly on my other lenses

Anyone else have any ideas, or should I be looking to return this lens or find a Canon repair shop to fix it?

I'm assuming it would be under manufactor warranty on day 1.

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If you bought it from a bricks and mortar store I would take the lens (with all packing and docs) plus your camera to the store and demonstrate the issue.  They should either be able to resolve the issue or find a solution - replace or repair the unit.

If you bought it on line then I suggest you contact the vendor.  As it is apparently new, it should be under warranty from the vendor or by Canon if it is not a grey market or overseas unit.

[Nick2020]

Hi nullgate,

Thanks for checking in.

It is possible that your lens is not working as it should, but keep in mind that lens, and any other lens with a stepper motor (STM), involves focus-by-wire manual focus, which is a little different than other lenses without the STM motor. On your lens, manual focus is triggered by the motor that reacts to the focus ring. For best results, you'll want to switch the lens slider to the M position and then press and hold the shutter halfway down before trying to manually focus. It might help to do the same when you switch back to autofocus.

If you continue to suspect an issue, then you may wish to send the lens to us for examination.

The repair options will vary depending on your location and are subject to change, so I would suggest that you email to get the latest repair details for your area:

eosdigitalsupport@cits.canon.com

[ebiggs1]

"Anyone else have any ideas, ..."

It is probably OK and you just don't understand how this type lens works. Do what Nick (Canon guy) suggests.  The focus ring probably feels like it isn't doing anything. That's OK.

[nullgate]

Thanks for the suggestions. I ended up returning this lens and purchased a new one that is working perfectly.