Problems caused by the Exakta 66 Mk 3 MLU
This device is badly designed in my eyes.
The shutter release is normally done automatically and quickly by the upgoing mirror (the shutter release button just releases the mirror). In case of mirror pre-release the shutter is prevented to start by a pushed cable release, and started by letting the cable release go. This has an impact on shutter speeds, it is not possible to start the shutter as precisely as the mirror does in normal operation mode. Shutter speeds are varying in a wide range. I tried it out and found huge, varying aberrations. I have even experienced shutters which stayed open when released by the Pentacon MLU device.
In addition, the operation is complicated:
Cock shutter
Operate and lock rear cable release
Operate shutter release button: Mirror locks up
Unlock rear cable release to release shutter
Even more complicated with „B“-Times. You need two cable releases:
Cock shutter
Operate and lock rear cable release
Operate and lock front cable release: Mirror locks up
Unlock rear cable release: Shutter opens
Unlock front cable release: Shutter closes
The MLU device is sensitive to wrong operation:
You may never cock the shutter with the (rear) cable release operated. If this happens, it is fatal: the shutter is set to the 1/1000 slit and won´t reset, meaning that a 3mm slit will remain between the curtains when they are moving across the film aperture during shutter cocking! Reset is only possible with taken off film advance lever! Hardly a DIY job...
If you need MLU, have a look at the baierfoto Two-Step-Release Device please.