X flash synchronization for flashbulb only shutters?

[Mike Wilde]

Does anyone have experience trying the preflash suppressor slaves for using a camera with only M synch with electronic flash?

A lot of the digital camers use preflash to set white balance, and so off camera strobes need to deal with this.

I would like to use few of my old cameras with electronic flash, but , as expected, the PC connection is timed to trigger early to let M speed flash bulbs build thier light before the shutter opens. They work just fine in firing my stash of flash bulbs, however.

I was thinking of getting a puny flash and filtering its output from the M terminal to emit only the IR (ie black slide film over the flash reflector window). This in turn cound trigger the preflash suppressor slave. However the preflash supperssor slaves are not too cheap, and I a have a whole collection of non delayed units already.

The other course of action is to build a monostable delay timer out of a pair of 555's and set the output to delay 20ms or so after the M contacts close. That is a bit of work that may be avoided if there is feedback that there is an easier way with commercial products.

 

[Allan Swindles]

Could you not simply use 'B' and trigger flash unit/s manually?

 

[Charles Webb]

It is not a big deal to adjust your contacts to zero delay. With an Ohm meter connect to 1 side of the contact and the other to the ground. trip the shutter and hold at wide open, bend the contact to exactly touch it's other contact point. Trip the shuitter as if you were taking the picture, if the shutter contacts close when the shutter reaches it's widest point, you are done if not try again. An M setting is generally around 20 miliseconds contact before the shutter reaches it's widest opening. X is wide open. To check for x sync, stop the lens down to about .16 or .22 place your strobe so it can be fired directly into the lens and shutter, trip the shutter
as your are looking directly into the rear element. If you see a perfect circle of light you are fine, hower if you see only a partial circle it's not X synced.

Charlie......................................

 

[Sirius Glass]

Most likely it is X synchronization if it is not marked. If both are there, M synchronization would be marked.

Leaf shutters defaulted to X sychronizationsince there was no need for the long flash times. With X synchronization, any shutter speed could be used and the f/stop was set by taking the guide number and dividing by the distance.

Focal plane shutters before the early 1960's [possibly 1950's] defaulted to M synchronization so that the shutter could use flash at higher shutter speeds.

Steve