MC-11 is not a remote release. It is the power cord between MD-4 and MA-4. Both MC-10 and MC-12 works with all the motor drives and camera you mentioned (MD-2, MD-4, MD-15, F4). Both can turn the metter on and activate autofocus with F4 when you press the button half way. The MC-10 does not have a trigger lock but the MC-12 has it. This means that MC-12 can work with the Bulb setting while the MC-10 cannot. If you use the MC-10 with the Bulb setting, the shutter opens but you will have to move the shutter speed dial out of the Bulb setting to close the shutter. MC-12 is the original version with a straight plug. MC-12A is the replacement with an angled plug. They are both 3m long. MC-12B is the same as MC-12A but is 1m long. There is only one version of MC-10 (ie. straight plug) and is 3m long. /Isaac
