Error 99 on 20d. Only @ Aperture other than f/4

So I have read a lot of posts about error 99, but so far I still haven't heard of anyone having the same problem as me so I will post about it. I only get an Error 99 when using my Tokina 12-24mm f/4 and only if the aperture is set at anything except 4.0. I can shoot all day at f/4 with no codes and no problems, but as as soon as I change the aperture it immediately throws an Error 99.

Anyone have any ideas?

Most likely the lens is failing to stop down when commanded to by the camera.

Has this lens worked on this camera in the past? If so, it may just be a problem with the electrical contacts. The first step would be to try removing and refitting the lens.

I have been using the lens for over a year with no problems. I have taken it on an off, cleaned the contacts, reset all the settings on the body etc. Still having the exact same problem.

You didn't say if your 50 has the problem also?

If your 50 works fine then there is something wrong with the 12-24.

DDCSD wrote in post #5963612
You didn't say if your 50 has the problem also?

If you 50 works fine then there is something wrong with the 12-24.

I agree...sounds like it is most likely a lens problem...especially if your other lenses work with not problems...good luck

If it is the lens and it is out of warranty, drop it (the lens) from about 2 feet (not attached to the camera) onto a carpeted floor. That might loosen things up.

50mm works fine.

I called Tokina and they said that I should send it in (even though I don't have a receipt) with the warranty card and they will fix it. They said they have about a two week turnaround time. Wish me luck :/

Let us know how it turns out!

For sure! Im not looking forward to being without that lens for 2 weeks (or however long it will actually take)