HOW-TO TUTORIAL: Replacing a Canon lens foot

[FlyingSquirrel]

I just replaced my Canon 500mm f4 IS ii lens foot with a Really Right Stuff lens foot. In my opinion there is potential for someone to screw this up if they are not familiar with this kind of thing. Hence, I thought I would post the instructions in hope it will help someone that needs a little help. Please note that I accept no liability or blame for any damage or other issues if you do this, and I don't claim that this procedure is the correct procedure. If you don't want to accept the risk, have canon do it.

The Canon lens manual clearly states that you should not remove or replace the lens foot by yourself. They say to take it to a licensed service center, due to special mounting requirements and safety. In my opinion, the following factors are involved: The lens is valuable and if you screw it up, you are screwed. The metal where the foot mounts is soft (aluminum) so too much tightening or other mess-ups can strip the threads. The best way to mount is with a special threadlock to avoid inadvertent loosening of the screws. It is my impression that this combination of factors leads Canon to recommend service by them.

Luckily for me, I am rather good at using my hands and mechanical type stuff, am careful, and have a bit of knowledge regarding what should and should not be done. My brother knows even more, so he was there to advise as well.

I put the lens down on bubble wrap, without the camera attached, and with the lens hood on to protect the glass. With any fragile equipment, I recommend working on a carpeted surface with bubble wrap or plastic bags, and in a clean area. You obviously don't want to do this on a table or counter top and have your lens roll off and smash into the ground (or maybe you do, I don't know ) Using the RRS supplied allen wrench, I carefully removed the screws from the Canon lens foot. (This was rather painful considering the lens cost 10K+ and here I am pulling it apart). Canon factory uses a light threadlock on the screws, so a small bit of pressure breaks them loose and then they come out easy. Next I tested the RRS foot. I fit the RRS foot on, carefully hand tightened the screws, then gave them a VERY minute amount of tightening with the wrench. I attached the lens and body, put the rig on the tripod, and balanced it.

When I was satisfied that things were good, I removed the rig, detached lens/body, and put the lens on the floor again. Then I backed out one screw from the foot, and, wearing rubber gloves, put a minuscule amount of BLUE 242 THREADLOCK on the screw (just enough to cover from the tip up to about 3/4 way up, without any excess globs), and re-inserted the screw. You DO NOT want to use the wrong threadlock. Blue 242 is made to be able to be broken loose with hand tools should you need to disassemble. If you use too strong of a threadlock, you are asking for trouble. I hand turned the screws a little bit to make sure the threads were not cross threaded. When it felt smooth, I used the allen wrench to put it the rest of the way in, then upon contact with the metal, I gave it a VERY VERY LIGHT amount of tightening. Literally a few millimeters of turn after the screw contacts the metal. Too much turn and you will strip the threads. I repeated this procedure for the remaining 3 screws. Then I put the lens in a camera bag with the lens foot upward, and made sure the bag lid did not put weight on the lens foot. Leave this for 24 hours for full curing of the threadlock. Then it will be ready for use. Again, I want to stress: Please note that I accept no liability or blame for any damage or other issues if you do this, and I don't claim that this procedure is the correct procedure. If you don't want to accept the risk, have canon do it.

Some pics of the lens foot and RRS cradle clamp on wimberley head. (these were taken on the test fitting, prior to threadlock application)

[Bobobird]

Thanks for the great info.

I have yet to slip my RRS foot but did replace the big one with the one for monopods. Quite a simple procedure overall and the screws are long enough to take a secure hold. Small foot has not budged for the 2-3 weeks that the lens has been in use. Reason for the RRS though is that I do not need to attach and extra plate for mono/tripod use and it is much much lighter too.

Normally I just have a BR Sport strap on the foot but if using the monopod will place the strap on the camera tripod mounting.

Thanks for the lock glue tip - might get one though from what others have so far done with their big lens none have mentioned a need for it. But better safe I suppose.

[Bobobird]

Now I know why the "glue". The screws for the Canon foot/feet are recessed into the foot. There is no recess in the RRS replacement so the screw heads stick out. In such cases it is better that a bit of that stuff is applied.

[FlyingSquirrel]

Now I know why the "glue". The screws for the Canon foot/feet are recessed into the foot. There is no recess in the RRS replacement so the screw heads stick out. In such cases it is better that a bit of that stuff is applied.

That is a valid point, however my main reasoning points are:

1. Canon uses threadlock from the factory. If they do, why would I not?
2. This is a large lens that weighs a lot and will be swinging around on a gimbal and I might use the foot as a hand hold as well. With that much activity on the attachment, over time, loosening is possible.
3. Threadlock if done correctly is not harmful, only helpful. Better safe than sorry.

[Bobobird]

Certainly agree especially since I hang mine off a BR strap and use it mainly hand-held.

But for winters it will probably sit on a tripod with the BR attached to the camera and lifted off whenever action takes place.

Still at 2 minds about the gimbal vs fluid head. Tested the latter extensively in the shop. Stability and flexibility of use was outstanding. Only issue is the tripod + head + camera + lens will be an awfully heavy combo to carry around and certainly cut down my very reason for photography - exercise from walking.