Mirror Lock has to occur under the control of the user, not the timer. For some lens, the mirror has to be up in order to mount the lens.
Mirror Lock means it stays ups as long as you want and will not return to the down position. It also means you trip the shutter anytime and as many times as you want. You can even use your motor drive for rapid exposure, all while the mirror is locked up.
I don't think that is what you are describing is it? :rolleyes: