Lens mount gap with heavy lenses 70d and EF 300mm f4

[RJU]

I'm probably being too critical, but has anyone else experienced this? I just recently bought a used EF 300mm F4 L, almost like new. I know to handle the lens/body combo by the lens due to the weight, but when switching hands (etc), i've noticed a bit of "sag" in the lens mount interface. The photos are the 70d/lens at rest, and then me pulling down a bit on the end of the lens. It seems like the body mount springs still have a bit of give to them when the lens is mounted. I've tried this on both of my 70d's, and my 60d. the 70d's have had more use, and do it a bit more. I've also tried this with my second biggest lens, my EF 70-200mm f4 L, and it will do it a bit, but not as much. Is this this just a normal effect given the weight of the lens? I used to have a Maxxum 9, and a Sigma 300mm f4 APO, and I don't remember it feeling like this, but that equipent was brand new, and I only had it a short time before i switched to the EOS 20d system. Any thoughts?

[ebiggs1]

I would think any noticeable amount of movement isn't good. I can't see the difference between the 70-200mm and 300mm making a great deal of difference. The ef 300mm f4 isn't a real heavy lens. You could have some mount wear on either or both the lens and/or camera, I guess. I haven't noticed lose fitting lenses and I use my gear a lot way more than most people. Or it could be tolerance stacking in play. If you are aware of it you can make sure you hold the lens tight to the camera and all should work OK. I doubt Canon services the 70D any more so that is not an option. A private shop can probably replace the mount for you.

One of the problems with buying used gear is you never know how used it is. Try before you buy!

[wq9nsc · Accepted solution]

There is going to be a little bit of slack/clearance or you would never be able to install or remove the lens and it would also quickly destroy the weather seal gasket.

I have a pair of 1DX II and 1DX III bodies and I can feel a bit of lens to body mount play when pressure is applied with all four 1DX series bodies using Canon "great white" telephoto primes.  The play is the same from the oldest body (a 1DX II from shortly after they were introduced to my newest 1DX III which is about 2 months old) across all of the primes from one that is nearly a decade old to a pair that are only a couple of years old.

If the lens wobbles around while you are just properly holding the camera and body then you might be concerned but applying pressure is going to cause some movement at the interface joint and that also happens with a $15,000 lens on a $6,000 body and they work just fine taking sharp photos as intended.

Realize that these cameras were designed to operate over a fairly wide temperature range and if they were so tight to be movement free at one temperature, they would likely become stuck at the other end of the range.  

I have never owned a 70D so I don't know how the frame of it is constructed but there is likely some additional frame flex within the body "skin".  The 1DX series use magnesium alloy construction to provide good support for very heavy glass like the EF 800 f5.6 so I suspect with this series all of the flex is at the lens to body interface but other cameras probably have a little additional free play within the frame.

Rodger

[ebiggs1]

Rodger I just checked my Sigma 150-600mm S on my 1DX and I don't see any real movement. Its the heaviest lens I have right now and just happened to be shooting with it.. It is very heavy by my standards. I don't think if you can see the gap it is a good thing like the example shows. Especially on a not really heavy ef 300mm f4L I'll go get mine and try it later.

I can try my old 600mm f4L, too. It and the Siggy S are about the same weight I think but I never use anymore  it since I got the S lens.

As to the rubber weather seal I doubt a tight fitting lens will wear appreciably faster because it folds inside and doesn't really rub the mount. I mean it does but its petty soft.