Does anyone know of a way to keep the shutter speed from creeping during a zoom?

With the EF 70-200 f/4 IS, in movie mode (not exp. sim.), I can mess with the brightness and hope the camera will hit upon the values I want by accident (1/60, f/4, ISO 1600, in one example), then I "lock" the exposure and begin recording. If I zoom during the shot, the shutter speed will get faster to match the focal length (1/60 at 70mm to 1/125 at 135mm, for example), and it increases the ISO to match. It changes those values despite (maybe out of spite?) the AE lock and running tally lamp.

Does everyone (anyone?) else experience the same problem? Is there any workaround? Thanks in advance.

I haven't tried what you're referring to (I no longer like zooming during a take), but what you say has been discussed here previously. It's a problem (or "feature" if you like) with this camera in it current incarnation. I don't think there is a solution, but hopefully I'm wrong.

Unfortunately for Canon, the solution is to use an adapter and Nikon manual lenses - or to unlock your lens and rotate it two or three mm.

what you say has been discussed here previously.

I was misreading some of the other threads, probably because I couldn't believe Canon would cripple the camera so (on top of everything else), but I see it now.

Thanks, guys.

I thought after locked (exposure), it stays locked in. Isn't that so?

some zoom lenses will change the aperature if you zoom them while shooting video....

some zoom lenses will change the aperature if you zoom them while shooting video....Only while recording? Or even after locked before recording?

My experience with the exposure lock option on a few other video cameras is that the exposure will remained locked, unless you fully zoom in while shooting and the camcorder can't maintain the locked combination of gain, aperture and shutter. Then it does the best that it can.

I thought after locked (exposure), it stays locked in. Isn't that so?

Unfortunately, it's not so. Canon's braindamaged AE system chooses shutter speed based on the focal length of the lens. This misguided desire to use the "1/focal length" rule is so strong that it even overrides the exposure lock, and will manipulate ISO to change shutter speed in the middle of a recorded shot simply because the lens was zoomed.

Other than that, I'm not aware of anything else that changes during exposure lock.

some zoom lenses will change the aperature if you zoom them while shooting video....

Yeah, I wouldn't mind the AE system compensating with ISO in that case (or not, I don't mind either way), but that's not what this thread is about.

My experience with the exposure lock option on a few other video cameras is that the exposure will remained locked, unless you fully zoom in while shooting and the camcorder can't maintain the locked combination of gain, aperture and shutter. Then it does the best that it can.

I have high hopes that Canon will get it right next time, because even their $100 digicams and camcorders don't make this mistake (or several of the other things that the 5d2 gets wrong).