Here is a description of the functions for the settings on the rotating selector dial:
"O" stands for "operate", and is the normal setting. When you press the release button, one exposure is made, and then the camera stops in the normal position with the mirror down and the rear flaps closed.
"S" stands for "side", or "pre-release". This setting is used to eliminate the vibration caused when the mirror flips up and the rear flaps open. You would use this setting when the camera is on a tripod, and you are using a very long lens or long shutter speeds. When you move the dial to the "S" setting, the mirror flips up and the rear flaps open, and the shutter in the lens closes. No exposure has been made yet. When you press the release button, the exposure is made. The camera is now in the normal mode, with the mirror down and the rear flaps closed.
"SR" stands for "side release", and is the same as the "S" setting, with the exception that when the exposure has been completed, the camera returns to the "S" setting, with the mirror up, the rear flaps open, and the lens shutter closed. This setting would be used if you were making a number of exposures in a row, using the "S" function setting. Not a commonly used setting.
"A" is the "automatic" mode, where the camera takes pictures at the rate of about 1 frame per second as long as the release button is held in. After the camera makes the last exposure, it returns to the normal position with the mirror down and the rear flaps closed.
"AS" is the "automatic side" mode, and operates exactly as the "A" mode, with the exception that after the last exposure is made, the camera returns to the "side" mode, as described in the "S" setting above. This setting is rarely used.
Here is a description of the features of the "LOT" switch:
"L" stands for "lock", and the camera can not be fired in this position. You would set the switch to this setting to prevent the camera from accidentally firing, when not being used, or when transporting the camera.
"O" stands for "operate". You would set the switch to this setting when using the camera.
"T" stands for "time exposures". You would set the switch to this setting when making exposures for longer than one second. Let's say that you wanted to make a five second exposure. You would set the shutter speed setting on the lens to "B". When you want to start the exposure, you would move the lever to the "T" setting. This begins the exposure. Five seconds later, you would move the lever from the "T" setting to the "O" setting to end the exposure. The lens shutter would close, ending the exposure, then the camera would wind to the next frame, the lens shutter would open, the mirror would be in the down position, and the rear flaps would close. The camera would now be in the normal setting.
I realize that this may all sound a little confusing. So here's what I'd suggest ... Put a lens on the camera and remove the film magazine. Then "dry fire" the camera at all of the different settings, and observe the functions of the camera and the lens. Once you see what happens at each of the different settings, it should be much clearer to you.
One other thing to note ... when using shutter speeds slower than about 1/30 second, make sure you hold the release button in until the exposure is finished. If you let go of the release button before the lens has closed, the camera will start to advance the film before the exposure has been completed, causing a streaked image.
David S. Odess
Factory trained Hasselblad technician
www.david-odess.com