Copal shutter firing flash multiple times per exposure

[williaty]

I recently bought a lens in a Copal 3 shutter and tested the shutter as soon as I got it. Sadly, I didn't test the X-sync port. From 1/125th down to 1/15th, the shutter fires the strobe correctly. At 1/8th, sometimes it fires the strobe just once and sometimes it fires it twice. At 1/4er and below, it fires the strobe repeatedly so fast it sounds like it sizzles for the duration of the exposure.

Does anyone recognize this fault? Do you know how serious of a repair it's likely to be?

Thanks for any info you have.

[Tin Can]

I have not seen this, but I almost always shoot flash at 1/30 on Leaf shutters so it's close to my Packard speed. Standardize.

Are trying for an ambient light effect?

Remember 35mm usually synced at 1/60th. Maybe for a good mechanical reason.

Sounds like points bounce.

[williaty]

I was trying to balance the strobes on the model inside against the sunlight in the woods outside the window. The Fujinon SF lens I was working with has a maximum aperture of f/10, so the shutter speed had to fall quite a bit for the ambient exposure.

[Liquid Artist]

I would look at the flash settings first, or at least try it with another shutter.

I do have a Metz flash that does the same thing on one setting, which I assume that it was designed to do.

[LabRat]

The internal flash contacts probably need cleaning... If the speed is slow, the contacts make contact, but if the contacts are intermittent, it may multi-fire as the contacts are not making perfect contact through the cycle...

Many old contacts are oxidized or burnt, but there might be another connector to the flash that also might need cleaning or replacement...

Steve K

[Two23]

I shoot a lot of flash over the past 12 years, mostly with a Nikon DSLR. (I use up to 16 flash, radio triggered.) My thinking is you have a sync cord that is shorted. This is the first place I look when this happens to me. The contacts are a possibility, but I just don't think they would cause flash to over and over. A shorted cord absolutely can and does.


Kent in SD

[williaty]

The strobes and sync cord works fine with every lens and camera except this one.

[Two23]

Somewhere there is a short. Might be in the wires of the switch inside the shutter. The only other possibility I can think of is the contacts somehow become stuck in the closed position.


Kent in SD

[Two23]

I'm home sick today, too sick to go anywhere but not so sick I'm staying in bed. I dug out my Nikon 90mm f4.5 lens in Copal shutter. It's in Copal 0 and not Copal 3, but I'm betting they work the same. I hooked up a Nikon SB-25 to a CyberSync trigger, then hooked up a Cybersync transmitter directly to the shutter. Fired at 1/250s--perfect. Fired at 1/60s--perfect. Fired at 1/30s--perfect. I cut the power from 1/1 to 1/64 as the recycle rate is pretty much instant. Fired flash at 1/15s--perfect, fired at 1/4s--flash fired twice! Set shutter to "B" mode, depressed shutter and held it for 10 seconds. Flash fired multiple times, which was what you were seeing. As long as the shutter is open, the flash seems to be able to fire. At shorter settings the flash does not have enough time to recycle and fire more than once. I've come across this before with other Copal shutters with same result. As long as shutter is open, flash will fire.


Kent in SD

[Neal Chaves]

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.

[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?threads/how-to-measure-pc-flash-sync-port-ohms-hasselblad-500c-m.131648/#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.