HELP. My 20D and 70-200 2.8IS not getting along.

About 6 times during a 2 hour shoot this weekend our camera stopped firing. The first time I couldn't figure out the problem. Then, I noticed the aperture was reading 0.0 so I narrowed it quickly to the lens.

Taking the lens off and putting it back on solves the problem instantly.

mminnig wrote in post #8436203
About 6 times during a 2 hour shoot this weekend our camera stopped firing. The first time I couldn't figure out the problem. Then, I noticed the aperture was reading 0.0 so I narrowed it quickly to the lens.

Taking the lens off and putting it back on solves the problem instantly.

Clean the electrical contacts on both the camera and lens side of the lens mount.

To properly clean the contacts: Use a lint-free cloth, lightly moistened with 93% rubbing alcohol, and wipe the contacts. Use a dry portion of the cloth after the cleaning pass to dry off any remaining alcohol/water (the 7% not accounted for on the label is essentially water).

DO NOT use an eraser on the contacts. That will damage the gold plating on the contacts.

something to check:
set the body to Av mode & F/16 and press the DOF preview button - looking thru the viewfinder you should be able to confirm the apeture blades in the lens aren't sticking.

something else to check:
if the body won't fire with no lens on at all, then the body's got problems no amount of contact cleaning will help.

Thanks for all of your advice! I just confirmed that the camera does fire without a lens attached.

Hmmm... the 70-200 2.8 IS is 6 months old..... the 20D is 4 years old..... I'm guessing it is the camera's contacts that are the culprit.

So... we are talking about the tiny, gold, pin-type things (8 of them) inside the bottom of the lens mount on the body? And, I'm supposed to rub them gently with a lint-free cloth....

mminnig wrote in post #8436988
So... we are talking about the tiny, gold, pin-type things (8 of them) inside the bottom of the lens mount on the body? And, I'm supposed to rub them gently with a lint-free cloth....

yes - that's them, also the associated contacts on the back of the lens...

Well. I'm hoping it was that easy. (fingers crossed)
Once again. POTN comes through with a solution in under 15 minutes.