Hello,

What are the facts I need to know before I use these bulbs? I have been using GE 5s and 11s or Sylvania Press 25s and 40s fired from my flash gun with the Supermatic (X) shutter. Are the SFs focal plane bulbs? What's different about them? Someone is offering me a bunch *******, and I want to find out if I can use them and what is diffent about them.

Thanks,

Keith

If those are the bulbs with no wire, only a gas filling, they're something like 5 ms ignition time, 5 ms burn time, with a pretty weak guide number. They require either an F synch or X synch (leaf shutter) at 1/100 or slower; they were used to stop motion when, for one reason or another, it wasn't practical to use a conventional bulb with 1/200 shutter (IMO, the better way to work, unless high film speed and close subject distance make the required aperture impossibly tiny).