Canon Rebel T7/Sigma 150-600 - Lens detaches itself

Hello - I am using a Sigma 150-600 Contemporary lens that seems to "unscrew" itself from the camera body mount periodically. The lens fell twice and I sent it to Sigma to get checked out. They replaced the mount but it happened a couple of times since then (luckily the lens did not fall). I am typically shooting birds, so I do zoom in/out frequently.

Has anyone had this happen? Is there a problem with the camera body or am I just "carrying/using it wrong"? I typically have it slung across my body, lens facing down. I am using a Peak Design Slide strap with one anchor on the camera body (top left) and one on the lens mount.

Any tips or solutions would be appreciated. Thanks!

I have that lens and have never had any issues like that.  Could you be accidentally pushing the lens release?  Maybe while carrying it facing down the button is being pressed by a belt/belt loop, or a strap somewhere?

mdmarqphoto wrote:

Could you be accidentally pushing the lens release?

I don't think so... originally I thought that may be it, but I've been watching for that and am pretty sure that is not it.

Do you think the zoom movement could be doing it? The lens zoom ring has some resistance and I'm now wondering if the zoom in/out is somehow rotating the lens out of the camera mount.

Rakeshg wrote:

mdmarqphoto wrote:

Could you be accidentally pushing the lens release?

I don't think so... originally I thought that may be it, but I've been watching for that and am pretty sure that is not it.

Do you think the zoom movement could be doing it? The lens zoom ring has some resistance and I'm now wondering if the zoom in/out is somehow rotating the lens out of the camera mount.

The lock is in the camera, so any turning of the lens should not release it unless there is a problem in the camera.  Maybe the locking pin/mechanism in the camera is worn.  Have you tried mounting another lens and see if you can get it to turn without pushing the release button?

Digirame wrote:

I've never had that happen with my Canon T3i (600D) or Canon T7i (800D) cameras and the Tamron 150-600mm lens or with any lens for that matter. Maybe you can rent another camera body like the Canon T7i (800D) and see if the problem persists.

If I remember correctly, the Tamron and Canon 150-600 zoom in/out in opposite directions?  I'm concerned that my zoom movement may be causing it detach from the camera mount.

On my camera, I don't hear an audible "click" when attaching any lens (even the kit ones). I guess renting a different camera is a good option, so will try that.

mdmarqphoto wrote:

The lock is in the camera, so any turning of the lens should not release it unless there is a problem in the camera. Maybe the locking pin/mechanism in the camera is worn. Have you tried mounting another lens and see if you can get it to turn without pushing the release button?

I tried with the standard kit lens and it seems solid. Even with the Sigma lens, normally I cannot get it to move without the lens release. It's just really odd that it's happened so frequently and I can't figure out the pattern.

The pin seems to look normal. I don't hear a "click" sound though, it's more of a "thunk" (when the lens and camera markings align. If I use my hands to move the lens, there is just a little bit of play, but it doesn't unscrew.

I guess I will just have to keep a watch on it and see if I can figure out what could be happening. Thanks again for your help

Digirame wrote:

That seems quite bad. I've never had that happen with my Canon T3i (600D) or Canon T7i (800D) cameras and the Tamron 150-600mm lens or with any lens for that matter. Maybe you can rent another camera body like the Canon T7i (800D) and see if the problem persists. The lens should lock in place. My guess is that it's your camera body that's causing the problem, but that's a total complete guess.

It should lock with a click. MY guess is your click lock on your camera is damaged, and the weight of the lens plus zooming cause it to unlock.  I doubt it is the lens other than the size/weight.

Rakeshg wrote:

The pin seems to look normal. I don't hear a "click" sound though, it's more of a "thunk" (when the lens and camera markings align. If I use my hands to move the lens, there is just a little bit of play, but it doesn't unscrew.

I guess I will just have to keep a watch on it and see if I can figure out what could be happening. Thanks again for your help

See above but it sounds like it worn and again the weight/motion combo causes it to be an issue.  Buy a used rebel XT for 60 bucks and see if its an issue, the mounts are the same. Or rent one, or lend me your lens and I try it out to see if its a lens issue. (or a friend)

Toronto Photography wrote:

See above but it sounds like it worn and again the weight/motion combo causes it to be an issue.

I think it was (is?) an issue with how I had the strap connected. I noticed that the release button was facing in and could be jostled by my hip. I changed the orientation of the strap and also connected it to the lens mount and now the camera faces outward. So far, I have not had it happen again, so keeping my fingers crossed.🤞

tkbslc wrote:

can you twist the lens off yourself without pushing down on the button?

You aren't inadvertently resting your hand on the release when supporting the lens?

I changed the way I had my strap connected (now the camera faces away from my body) and so far, it has not happened. I think I may have been jostling the release with my hip but can't be certain.