Forcing aperture with old EF lenses

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    I just got a really amazing Quantaray 24mm f/2.8
    But… using it with an aperture other than wide open crashes my Rebel XT with “Error 99”
    Is there a way to force it to go to a certain aperture without letting my camera know?


    On a Nikon we set the ring to 22 and leave it there. The camera does the aperture.


    If you google Canon “Error 99” you’ll find a lot of pages where this is discussed. Nobody seems to have an exact answer, some claim it is a general error message when the camera crashes, but most of the reports have been related to third party lenses, or with dirty lens contacts. I had that error a couple of times with a Canon 24-70mm lens; I cleaned the lens and body electrical contacts and the problem went away.

    I’d try cleaning the lens contacts first (I’m assuming this doesn’t happen with your other lenses, so it’s probably not the body contacts). Some use a pencil eraser, I used isopropyl alcohol and a swab. Barring that, perhaps someone has come across the same problem as you with that particular lens. Google that sucker 🙂

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