Large telephoto (300mm 2.8 IS) does not stay on 5D mount...

[sbrauchli]

Hi,

 

I recently acquired a beautiful EF 300mm 2.8 IS. The lens takes amazing

photos, but this weekend, I noticed some odd behavior. I had the collar

mounted on the lens, so I can hold on to the whole set-up from above when

walking around. The lens bracket (collar foot) was pointed upwards in the same

direction as the flash connector on top of the camera. I noticed that, even

though when I mounted the lens, it clicked into place, at times, the collar

(and the whole lens attached to it) would start rotating towards the right (as

though I was removing the lens). I pressed the lens release button and

remounted the lens. Again, after some time, the lens started to unmount.

There is a small pin on the 5Ds body that is supposed to lock the lens in place

by filling the small hole on the lens' mount ring. I assume, the weight of the

lens allows enough of a gap for that pin to slip out thereby unlocking the

lens, which could lead to the lens dropping off the body.

 

Has anyone else had this issue with any of the large canon lenses? Is there a

way to avoid this behavior? I would appreciate any help.

 

Thanks

[bryan_lardizabal]

Does this happen with any other lenses you have? If yes, I suspect a camera mount problem.

[mrossi]

My 100-400 definitely locks into place, I'd be quite nervous if it didn't.

[sattler123]

Neither my 100-400 nor my 500 have this problem on either my 5D or 40D - something is wrong with your mount (could be the lens or the body). Better have it checked out - this could end up in a catastrophy!

[sbrauchli]

Thanks. Yep my 100-400 locks just fine. It must be an issue with the lens then. I will try it out on the 40D to see if it happens there too. If so, I will ask Canon about it. Definitely not a thing I want to worry about when shooting.

[bob_sunley]

You should always be carrying the lens with the camera attached to it, not carrying the 2lb camera with a 6lb lens attached to it.

 

Pulling the lens mount flange off of the camera body is not uncommon with large heavy lenses.

 

Look at the lens mount where the lock pin rests, if it looks chewed up even slightly, that could be the only problem, otherwise, the weight of the lens might have pulled the lens mount flange loose enough that the pin slips out of the hole/slot in the lens. It's not uncommon for both to be damaged. :(

 

You should never carry the weight of a large heavy lens on the camera mount, always let the lens support the camera. A good rule is if the lens has a tripod mount, it is too heavy to be supported by the camera, which means don't use the neck strap on the camera when it is attached to a big lens.

[sbrauchli]

Thanks Bob. I do generally hold the camera by the tripod mount on the lens which is attached to the camera. I will check on the pin. Do you remove the camera carrying strap from the camera and use it on the lens?

[bob_sunley]

I have a nice shoulder strap I made from a belt and an old "bolt" that came from a flip open case for a 35mm camera.

[photographicsafaris]

Check if the hole that the pin goes into is not filled with gunk, or debris.

 

Then check that all the screws in the metal lens mount are not loose.

 

Lastly, check the metal lens mount on the lens to see if there are any missing or loose

screws.

 

And finally, see if you can notice any movement in the lens mount when lenses are

mounted and you "wobble" the lens around from side to side.

 

Cheers G

[sbrauchli]

Thanks Graham. I am confused. I checked the screws on the camera and the lens they are all tight. No gunk in the hole or anywhere else (the lens is new and looks it). I mounted my 100-400 on the 5D and mounted the 300 on the 40D, but could not move it. When I noticed the problem I had the camera strap around my neck and was holding the lens and camera much like a baby (so as to support the lens as well as teh camera and not have the full weight pulling on the body).

 

One thing I did notice is that the hole on teh 300 is much smaller and round whereas on the 100-400 it is more oval and bigger. I was not able to move the 300 though once it was mounted (seems to only happen when I carry it around for a while).

 

I will have to do some more experiments as soon as time permits. May want to look at another 300 to make sure mine does not have a hole-deficiency...

[danny_dench]

hello steven, just read about your problem, I to have a 5D with five other lenses all canon.

my favorite is the 70-200. all works with no problem. i have a 2x converter which i was

not happy with on this lens so i got the 1.4x. now then here we have something in

common for although there was no problem with the lens lock-up. putting on the 1.4x

converter found that we suddenly had a big automatic unlocking problem! this only when

using the 1.4 on the 70-200.

I have a neck strap as a safety, and hold on to the tripod collar with my left hand while

holding the camera with my right. I would see a bird coming my way raise the camera to

eye level half press the shutter release to auto focus and... nothing, looking at the lens

reveals that it has unlocked by 20-30 degrees. a good job i camera in one hand and lens

in other. I have checked this out over a mile walk around a bird sanctuary and it kept

coming undone 10 or 12 times. I have been over and over in my mind how is it possible

for me to hit the release button, for it is undoing from the camera and not the extender or

the lens. and yes it is firmly locked.

has anyone else had this.I've shook and rattled it checked it every 10 meters everything

ok, when suddenly its come undone! Auto-lens change. Now thats wasn't in the brochure!

yours danny

[sbrauchli]

Hi Danny,

 

I also have the 1.4X and the 70-200 2.8 IS, a great combo. I also find that at 2.0X you lose a lot of IQ. Well I don't know what it is, but with the 70-200, I don't have the problem. The 300 2.8 IS is however around 8 pounds, so I am always holding it with one hand when shooting. I also use the lens collar to hold the lens and camera assembly. I noticed the problem when walking around in a zoo, having the camrea strap around my neck and only lightly supporting the lens. I definitely am not hitting the release button. It seems to me like the long and heavy lenses somehow manage to separate enough from the mount to where the small pin holding them in place slips out, causing the eventual unmounting. This is definitely not something I expected. I wonder if this also happens with the PRO models such as the 1Ds. Since I have become aware of the issue I have been very careful to always hold the lens and never induce any torque by holding the camera without supporting the lens and I have not had the issue. Still it does not make me confident in my equipment. i would hate to lose the 300mm due to such a flimsy mount by Canon. With big game fishing trolling rod and reels you also clamp the reel onto the rod with screws (in addition to the conventional reel mount), so it would only make sense to have something similar in place for heavy lenses that cost a bunch of money....