Flash Sync Voltage- Vivitar 283

Looking at this recently I'd have to say most of the 'net sites have got it wrong. You really can't measure the flash sync voltage with a DVM. Using my ancient Vivitar 283 as an example, the DVM reading is about 10 VDC across the contacts, both shoe and PC socket. The fly in the ointment is that the charging waveform is part of that voltage. On an oscilloscope, the peak voltage is just over 16 volts. The DVM averages out the saw-tooth oscillator waveform for a lower reading that's of no relevance.

 

The problem is semiconductor devices only care about the peak voltage, so if a manufacturer says their hot shoe is only good for 6 volts (or whatever), that's the maximum it should ever see.

 

Still, my 16 volts is way better than other 283s that measure near 200 volts.

 

The other part of this whole sync safety thing is current. To fire a flash, they usually discharge a capacitor across a trigger coil. The energy depends on both the voltage and the value of the capacitor and at some point the poor camera may not be able to handle it. Unfortunately, nobody ever talks about that. Newer flashes will isolate all the above with additional circuitry, so I'd be wary of using any older flash unit with a newer camera unless you use one of the safe sync type devices.

Several years ago, I fooled around with using older electronic flashes with various cameras. However, I soon found it more practical to find used flashes actually made for my old cameras (they cost practically nothing)

 

However, I earlier did splurge on Wein Safe Sync connection (LINK, e.g., : Wein Safe-Sync Hot Shoe to Hot Shoe with PC). Like the charm I bought in Africa, it "kept the serpents away" so far as I could tell-- at least I never saw any serpents or had any electronics burnt out. ;)

 

Check out LINK (Photo Strobe Trigger Voltages) just in case. I have no idea if this is still "current", so to speak.

Several years ago, I fooled around with using older electronic flashes with various cameras. However, I soon found it more practical to find used flashes actually made for my old cameras (they cost practically nothing)

 

However, I earlier did splurge on Wein Safe Sync connection (LINK, e.g., : Wein Safe-Sync Hot Shoe to Hot Shoe with PC). Like the charm I bought in Africa, it "kept the serpents away" so far as I could tell-- at least I never saw any serpents or had any electronics burnt out. ;)

 

Check out LINK (Photo Strobe Trigger Voltages) just in case. I have no idea if this is still "current", so to speak.

 

 

I have a minty 283 with all sorts of useful (& some silly) accessories. Had researched the Wein device to be able to use the flash with digital. Asked the pro at a very good camera store (where I would have ordered it ) - he apparently had a customer or two with bad outcomes and recommended that I not get one. Obviously you have had a successful experience - this some additional info.

I recently emailed Nikon about my Z6 and they suggested the AS-15 adapter. The Z6 has the same rating as their other DSLRs, but reading between the lines, it would seem that accidentally contacting any of the other flash shoe contacts would result in disaster. Makes sense, as those are likely low level digital communication signals, though I don't see how it could happen while sliding things in and out. Being a bit timid, I picked up a SMDV SM-512 protection adapter on Amazon. Seems decent for the money, but I've yet to shoot with it. I'll report back...

Looking at this recently I'd have to say most of the 'net sites have got it wrong. You really can't measure the flash sync voltage with a DVM.

Too damn right Conrad!

 

I've ranted about this before on Pnet, and emailed the publisher of that stupid Botzilla list explaining the issues.

 

The correct voltage can be got with a DVM of known input resistance, but it involves taking a second reading with a resistor similar to that of the DVM impedance in series. The two voltage readings then allow calculation of the true trigger voltage at the hotshoe or P-C plug.

 

The old and common trigger circuit of a small capacitor being discharged via the synch contacts into an EHT auto-transformer is no longer used, than goodness, but there are many, many flashes on the used market that have it. The series 'safety' resistor used in such a circuit has a value of several (unspecified) megohms, and prevents a 10 megohm DVM from directly measuring the open-circuit voltage.

 

For example, a straight DVM reading of 200 volts might indicate that the true O/C voltage is actually closer to 350 volts, which well exceeds Nikon's 240v specification.

 

In fact, if you get a trigger reading above 150 volts from any flash by using a DVM, it's wise to assume that the true voltage will be 300 volts or greater. This is because most xenon flash tubes need a voltage of 300 to 350 volts to work efficiently.

 

Take care!

Edited February 2, 2020 by rodeo_joe|1

Ha! You, me and about 4 other people know the resistor trick. Good analog measurements are a lost art that I take much joy in.

It's clear that any meter except perhaps a valve voltmeter will depress the open circuit voltage because of its internal resistance. However I wonder if the safe synch voltages quoted by camera makers actually take this into account, perhaps they are based on measurements done in the usual way.

Limits are limits. They may add a safety factor, but probably not because of the difficulty of measuring flash sync. More likely to be sure that every single unit meets the spec. Remember, there's the impedance issue, but also the waveform issue. The DVM averages out the peaks. I should get a scope shot of that to make it clearer. The Nikon voltage limit is higher than most, but that would make me even more leery of getting too close, much less exceeding it.

 

My interest is, of course, because the modern fully compatible flashes are way beyond my budget and I don't use flash often enough to even remotely justify the price. I was also looking at some used studio units and wanted to be sure they were safe.

The fly in the ointment is that the charging waveform is part of that voltage. On an oscilloscope, the peak voltage is just over 16 volts.

Interesting.

I've never bothered to 'scope any trigger voltage that reads under 12v, and in any case the cycling period is usually long enough to see the voltage drop and climb on a DVM. Must get the Tektronix digital storage 'scope onto a few flash synch terminals.

 

You don't say what camera you're looking to fit a flash to Conrad, but I can vouch that there's no issue fitting most old (film era) Canon speedlites to a Nikon camera, and likewise with Nikon speedlights on a Canon body. Both Canon and Nikon flash-trigger voltages have been around 5v for years.

 

When the interchangeable SCA300 connector was introduced, its specification fixed the trigger voltage at no more than 24v, but companies like Sunpak and Vivitar continued to do their own thing with trigger voltages much higher on some models.

 

FWIW, my personal favourite choice of 'old' flashguns is Nikon's SB-25. It's as powerful as anything more recent, has a decent range of manual output levels, has an accurate and reliable Auto-Aperture mode, recycles from a full pop in 4 seconds and has a 5v trigger. The LCD interface is quick and intuitive to use as well, unlike the later SB-28 that only lets you change ISO speed immediately after switch on (madness!).

However I wonder if the safe synch voltages quoted by camera makers actually take this into account

Almost definitely not; and a bit of a naive question, if you don't mind me saying John.

Edited February 3, 2020 by rodeo_joe|1

I don't think it's unreasonable to suggest that safe voltages when given by manufacturers, are based on a method of measurement which can easily be performed with a widely available volt ohm meter, rather than using an oscilloscope to measure the waveform peak, or performing an Ohms law calculation to eliminate the depression of open circuit voltage due to the connection of an instrument.

Can't do it because the meter averages out the peaks and you don't know the waveform shape. It's not just the impedance problem- you're not dealing with a DC level, at least not on every flash.

I don't think it's unreasonable to suggest that safe voltages when given by manufacturers, are based on a method of measurement which can easily be performed with a widely available volt ohm meter...

Quoted 'safe' voltages are far more likely to be based on component specifications, or possibly on theoretical flashover spacing between PCB tracks or component spacing/size. Less likely is that a statistically significant number of cameras have been subjected to actual voltage tests. But in all cases the true voltage would be quoted.

 

Nobody in the electronics industry quotes tolerances based on a guess as to how the user might measure such tolerances. Although measurement conditions, such as temperature and humidity, might be specified somewhere in the small print.

 

Whatever. 250 volts is 250 volts, and if damage occurs because the end-user fails to measure an applied voltage correctly, then that's their fault, and not the OEM's.

Edited February 5, 2020 by rodeo_joe|1

The fly in the ointment is that the charging waveform is part of that voltage. On an oscilloscope, the peak voltage is just over 16 volts.

You piqued my curiosity there Conrad. So I checked out a few of the (too) many speedlights I have with my Tektronix storage scope.

Results follow:

 

1. Nikon SB-25 - a steady 3.5 volts that drops to zero when the flash is fired. It then quickly kicks back to 3 volts during recycling. There's an overshoot of about 1v, and a delayed step back up to 3.5v, but at no point did the voltage exceed 4.2 volts.

 

2. Nikon SB-28 - practically identical trigger-voltage behaviour to the SB-25. Maximum voltage overshoot was to 4.22 volts.

 

3. Canon 540Z - a maximum voltage of 3.86 volts was recorded, with sporadic voltage drops of about 0.4 volts lasting no more than 10 milliseconds every 100 ms or so.

 

4. YongNuo YN560 II - absolutely flatline at 4.14 volts. No variation during firing or recycling.

 

5. YongNuo YN560 III - ditto as above.

 

6. Cullman/Osram MD40 - an interesting one this. Peak voltage was 7.88 volts, but obviously at a high impedance, since it quickly dropped to only 2 volts as the 1 megohm probe was applied. Zero volts after triggering, which had a slow rise back to 2 volts under the 1 megohm load.

 

7.Sunpak Auto Zoom 2400 - obviously an 'old school' trigger circuit design here. Maximum voltage 302 v (!), which dropped to 180 volts over 600 ms when a 10 megohm probe was applied. FWIW, the resistance + DVM method of measuring that voltage gave me 308 volts in series with about 7 megohms by calculation.

 

Sooooo. None of the above flashes had a sawtooth trigger voltage waveform, and apart from the old Sunpak, none of them had a peak voltage that should really give any cause for concern. And if you need zero variation of trigger voltage, get a cheap YongNuo!

Edited February 6, 2020 by rodeo_joe|1

Interesting! I'll put up a photo of the Vivitar 283 waveform when I get a chance. All those newer flashes seem perfectly safe with any modern camera.

If there is sawtooth voltage on the sync input, it better still be able to flash on the low side.

I found that I can't measure the voltage of the 283 with my scope. My DMM reads about 280V and my scope can't take that high a voltage without special probe.

There are definitely multiple versions of the 283 with different trigger voltages. 280 is too high for anything and you need a safe- sync type device. I found a nice one, but it's limited to 60V, which seems low for such a device, but it gives me peace of mind for moderate voltage flashes, plus provides the PC socket.

There are definitely multiple versions of the 283 with different trigger voltages. 280 is too high for anything and you need a safe- sync type device. I found a nice one, but it's limited to 60V, which seems low for such a device, but it gives me peace of mind for moderate voltage flashes, plus provides the PC socket.

 

According to Vivitar there were several version of the 283. The one I have made in Japan has the 280V. Your may be made in Korea. Vivitar said the ones made in China would have 6V. The reason I want to measure it with the scope because I want to see the sawtooth wave you're talking about.

Sorry, but I just don't 'get' this fascination with, and almost cult status of, the Vivitar 283 and its siblings.

 

The lack of a swivel head makes it a complete non-starter for me. How do you bounce it off a wall, or off a ceiling in portrait orientation?

 

It also has at least half a stop less light output than any camera-maker's top speedlight.

 

The plugin modules needed to change mode are a joke, and there's no 'zoom' facility to change coverage angle. It's also pretty slow at recycling and used prices are well above what its features (or lack of) deserve.

 

Not even touching on the Russian roulette aspect of its trigger voltage.

 

Explain..... please.

Considering a new YongNuo 560 or used Nikon SB-25 can be had for about the same money.

Edited February 26, 2020 by rodeo_joe|1

Sorry, but I just don't 'get' this fascination with, and almost cult status of, the Vivitar 283 and its siblings.

 

The lack of a swivel head makes it a complete non-starter for me. How do you bounce it off a wall, or off a ceiling in portrait orientation?

 

It also has at least half a stop less light output than any camera-maker's top speedlight.

 

The plugin modules needed to change mode are a joke, and there's no 'zoom' facility to change coverage angle. It's also pretty slow at recycling and used prices are well above what its features (or lack of) deserve.

 

Not even touching on the Russian roulette aspect of its trigger voltage.

 

Explain..... please.

Considering a new YongNuo 560 or used Nikon SB-25 can be had for about the same money.

 

I got a 283 as a birthday present from my father in 1979 when I was otherwise using flashcubes.

(In an Agfalux C, which is pretty nice to carry around.)

 

The 283 might be a half stop less, but it covers a 35mm lens. When I bought my Nikon FM (in 1979),

I bought it with the AI 35/2.0, so the 283 worked well with that. But that was 40 years ago. I don't know what

others have done since, in terms of light output covering a 35mm lens.

 

There is a Vivitar lens kit, that allows for covering 24mm, 28mm, 70mm, and I think 150mm lenses.

The first two reduce light intensity (spreading over a larger area), and the latter increase it,

concentrating in a smaller area. I had one of those early, though never used it quite as much as I

thought I might. I did use the 24mm one with a 24mm lens.

 

There is also a cable for the 283 that lets you keep the sensor on the camera, and move flash head

anywhere you want, pointing in any direction. I have one, have used it, but again not as much as I

might have thought. Mostly for off camera non-bounce. It would work well bounce into an umbrella,

but I never tried that. Handheld, that would need three hands. (I believe the cable is

about 1m, so not completely anywhere, but anywhere you can reach while holding the camera.)

 

With NiCd batteries, it recycles pretty fast. Much slower with alkaline. I think fast with NiMH, too.

 

For really fast recycle times, there is an input for a high voltage cable. You can use external

power supplies, either line powered or large battery powered, to get really fast times.

(The design is for a 510V battery, but it is also used with other sources.)

 

I suppose for me, it is special being my first electronic flash unit, and works really

well for camera mounted non-bounce with slower (usually Ektachrome 100 at the time) films.

Not my first flash, but my second. It was top of the line at the time, or close. I've usually used a grip on 35mm SLRs or TLRs, with the handle easily removable and the flash mounted on that. I used the same long coil cable described above. Thus, it was really handy to slip off the handle of the grip and point the flash wherever I wanted, if only to improve the lighting direction. I've also got an ancient Gowland Soft-shoulder reflector I've used it with. Sure, not the ultimate flash, but for the money, used, they offer a lot. I wish I knew what year mine was made. It was made in China.

 

Finally took some snaps of the scope. When the flash is charging, the waveform is continuous. When it goes into battery save mode, the same waveform bursts about once a second. Not huge voltage here, just illustrating that a DVM doesn't tell you everything.

 

Vivatar 283/285 flashes were pretty good when they were introduced (mid 1970's, I think) but have obviously been surpassed in many ways by newer flash units. I think they are similar to Pentax K 1000 35 SLRs--decent value when they were new and thus remembered fondly but not a good choice now under current circumstances. I still own 3 285's that I use occasionally with slaves on manual and they work well after 25+ years. If I were buying new flashes now, would I choose these? Probably not, but for now they still do the job that I need them to do.

I was pretty good in the mid 1970's, but have also been surpassed in many ways...

The fond memories, nostalgia and 'it's what I've already got' is entirely understandable. But paying good money for a used one today? That's where my understanding fails.

 

The 35mm coverage is still limiting. If you put a flash into a brolly or softbox, you generally get a more even diffusion (i.e. softer light), and more light out, if the flash is set to its widest 'zoom' - like 24mm. This is a bit counter-intuitive, but it's to do with properly filling the reflective surface with light. Especially since a flash tends to self-block some of the reflected light from an umbrella.

 

Addendum: just tested an old Vivitar 283 that I picked up from a junk-bin sale. Its trigger voltage is a little over 330 volts according to my storage scope, and 325 volts with 2.1 megohms in series by the DVM + resistor method. No sign of any variation during inverter cycling though. But what's a couple of volts in 330?

Edited February 28, 2020 by rodeo_joe|1

The fond memories, nostalgia and 'it's what I've already got' is entirely understandable. But paying good money for a used one today? That's where my understanding fails.

 

The 35mm coverage is still limiting. If you put a flash into a brolly or softbox, you generally get a more even diffusion (i.e. softer light), and more light out, if the flash is set to its widest 'zoom' - like 24mm. This is a bit counter-intuitive, but it's to do with properly filling the reflective surface with light. Especially since a flash tends to self-block some of the reflected light from an umbrella.

 

Addendum: just tested an old Vivitar 283 that I picked up from a junk-bin sale. Its trigger voltage is a little over 330 volts according to my storage scope, and 325 volts with 2.1 megohms in series by the DVM + resistor method. No sign of any variation during inverter cycling though. But what's a couple of volts in 330?

 

I don't remember exactly but I bought my 283 recently and paid less than $5.