Copal shutter firing flash multiple times per exposure

[Two23]

The flash contacts in all leaf shutters bounce. This was never a problem with older electronic flash units, but with newer ones that store capacitor energy and are ready for the next flash almost instantaneously, you can have multiple pops.

Most flash require a 5-6 second recycle. Small Nikon SB type flash release their power all at once when on full power and take 5-6 seconds to recharge. When set to something like quarter power the capacitors are able to keep enough energy stored and be read for nearly instant release. The lower the power setting, the more this is true. Some newer monolights (such as Buff Einsteins) use the same circuitry (called IGBT) and they can cycle in as little as 1/10s. I suspect this is what is going on, if not a short of some kind. Looking at a diagram of a Copal shutter I can see how they might bounce inside. Not an issue with flash bulbs, short shutter settings, or flash set to full power (and thus longer recycle), but I just don't know if the flash would fire more than twice with a bounce. I tried all three Copal shutters I own and could not get a bounce. All three would do multiple fires while shutter was open. I had shutters in the vertical orientation as they would be on a camera. Too bad Copal shutters are so spooky to crack open and look!


Kent in SD

[Tin Can]

The SB 28 would do 16 pops on any Nikon in one exposure. I used that a few times.

Ever seen a ghost...

[Two23]

The SB 28 would do 16 pops on any Nikon in one exposure. I used that a few times.
.

High speed sync mode?


Kent in SD

[williaty]

High speed sync mode?


Kent in SD

No, all the flagship Nikon speedlights from the SB-28 (and maybe earlier) on have a repeating flash mode. You can tell the flash how many pops you want to do and how fast you want them and then you set it to first curtain sync with a shutter speed long enough to record all the pops and you get a stop-motion stroboscopic effect. I did a bunch of motion studies in college using that feature at night back in the film days. The only downside was that the faster (higher frequency) you wanted pops, the lower power you were limed to.

[Tin Can]

I don't know what it's called. I read about it in the manual when I bought in 1998 for my N70. I knew a place that claimed a ghost, I never saw despite me being there 24/7. So I made them a ghost. I stripped naked in a dark hallway and did a 16 pop tripod selfie. I jumped around and nobody could tell it was me or that I was naked. Made a print put it in a show and that one print is the only one anybody offered to buy. I don't sell prints. It was hilarious. People believe I captured a ghost. They still do. Boo!

The SB28 still works fine.

Sent from my iPod

[wombat2go]

http://www.apug.org/forum/index.php?.../#post-1736101
Here is a link to apug where i made oscilloscope trace of contact bouncing on an old
Mamiya RB67 Mamiya Sekor C 1:4.5 f=50mm

Hope the link is OK.