I'm using two separate shutter release cables to use the mirror lock up, and I'm having an issue. Here's what I'm doing: Release cable into the lens, release cable into the shutter release on the camera body. I first activate the release on the body, and the mirror goes up. I then activate the lens release, and the shutter closes after the appropriate amount of time. The problem I'm having is this. Between raising the mirror, and releasing the shutter, the shutter remains open. So, for example, if I wait 1 second between releasing the mirror and releasing the shutter for a 1/2 second exposure, I end up exposing the film for 1.5 seconds. Is this a problem with the lens, or am I don't something wrong?