Bought a used 150 Symmar. what is x or m setting?

[abiggs]

I just bought a Schneaider 5.6/150mm Symmar, and I noticed a switch on the side that has an 'X' and an 'M' setting.

What is this? I assume for flash sync.

[Richard Boulware]

The "X" sync is for strobe (no timing delay). The "M" is for flashbulbs. This delay was 20 miliseconds to allow to flash bulb to reach peak illumination before the shutter opened and closed. Richard Boulware - Denver

[Enrique Vila]

It is indeed for flash sync settings. If you are using electronic flash, you should set it to X.

[Kevin Crisp]

Andy: Unless you plan on using bulbs, it is not a bad idea to stick a little piece of gaffers tape across the opening so the switch can't get knocked over to M when you lease expect it.