I just purchased a used 135L and have noticed on 2 different occasions that the aperature will start auto-adjusting in Live View as I increase or decrease exposure. The camera still says aperture is at 2.0 and it still renders the picture wide-open...but the live wiew will be obviously stopped down. The first time it did it, I turned the camera off and back on, and it stopped doing it. I then cleaned the lens contacts up a bit with a pencil eraser. The second time it did it, I twisted the lens off and back on, and it quit doing it. So at this point I am thinking it is a lens issue, but wondered if anyone has had a similiar issue? The camera is a Canon 5D Mark III. When I press the DOF button it switches aperture back to wide-open, but only when it is pressed (like it's supposed to). When I release it, Live View returns to it's stopped down view, while at the bottom left it still says "2.0". Live View should always stay at a wide-open aperture, no matter what camera settings, correct?
***It's like the camera is auto-adjusting aperture to keep the Live View from over-exposing / under-exposing. Is there a camera setting that does this that I am unaware of?
Thank you for reading....
