My 150mm, f/4 T* Carl Ziess Sonar CF does not have "T" setting? Question: 1. Should I assume that I must use a cable release that can be locked down for long exposures? 2. In searching Googling for this answer, I found an astonishing observation. Ostensibly, after 30-seconds the lens or the shutter on the back closed? Any comments or guidance would be appreciated.