I have the Quantaray QTB-9500A flash unit with the Nikon dedicated module. Nikon advises that the trigger voltage on non-Nikon flashes be under 250V for the 990. Is anyone using this flash or has anyone tested the voltage on this unit? Thanks.

-- Dennis Pereira (dpereira@ultranet.com), July 17, 2000

Answers

There's been a lot of controversy over the flash voltage issue with Nikons. I turned the following info up while trying to find out what is safe to use with my Toshiba PDR-M70:

According to what I read, Nikon flashes use about a 5 Volt circuit. Some users are using third party flashes with around 8 Volts without any difficulties, so far... If the voltage is too high, the effects could be cummulative depending on the components used in the camera and a problem may not appear for some time. I have no opinion on this as I have no idea what actual components are being used or what their ratings are. If it was me, I'd stick to flashes with voltages no greater than the recommended Nikon units just to be safe. Nikon charges plenty for repairs from what I've seen in posts on the net.

Nikon has supposedly said(paraphrased) at various times:

"Only use our flashes..." "Flashes with trigger circuits under 15 Volts are safe..." "Flashes up to 250V are safe..."

I believe the 15 volt range might be safe, but the 250V figure probably refers to the maximum back EMF or bleed through from the trigger circuit that may unintentionally appear on the trigger terminals. I'd err on the side of caution and stick to the lower trigger voltage flash units or find some sort of isolator circuit to fire the flash like a slave unit. Unless the 250V figure is for the new 990?

You can determine the trigger voltage of any flash unit by simply turning the flash on and allowing it to charge up, then using a voltmeter[preferrably digital ;-)] to measure the DC voltage present across the sync or shoe terminals on the flash. I have a cheap($20) Vivitar 2000 flash that puts out 200 or more volts DC. Ouch!

Measuring any high voltage back EMF, etc. on a low power flash is a bit trickier. I expect you'd need to attach an oscilloscope to the shoe terminals on the flash and discharge it in a box or something in a darkened room so you can see the very brief fairly faint high voltage spike pulse on the scope without being blinded by the flash.

Personally, unless I was certain about what flash voltage is safe (getting it in writing from Nikon would make me feel more comfortable, for instance...), I'd err on the side of caution and use a slave unit or a unit recommended by Nikon.

On the other hand there's a website with a list of flashes reported to be safe with the Nikon 950 at:

http://angelfire.com/ga2/photo/flashpage.html

Like most things in life, "You pays your money, and you takes your chances..." :-)

Seems to me the Nikon website tech section should have something more definitive to say about all this!

-- Gerald M. Payne (gmp@surferz.net), July 17, 2000.

Thanks for the feedback. I went out and spent $20 on a digital voltmeter and measured 5.5V trigger voltage for the flash unit. Looks like it should be ok based on the Nikontech advice. Now I need some ideas on what else I can do with the voltmeter...

-- Dennis Pereira (dpereira@ultranet.com), July 18, 2000.

"Now I need some ideas on what else I can do with the voltmeter..."

1. Attach a solar cell to the leads and use it as a light meter?

2. Check the charge on your NiMH batteries with it?

3. Attach one lead to a copper penny and the other to a dime and insert both in the slice of lemon that comes with your Iced Tea to create a battery you can monitor with your meter? You'll impress your friends and convince them you're even more of a techno geek than they thought... Not to mention giving them a good laugh when you forget to remove the lemon from your tea? The strange looks you get from fellow diners or passersby while meter leads are strung from a lemon on your table might make for a nice collection of photos!

4. Uh, return it? [ -it wasn't the right color. -I checked my synaptic potentials and they were fine. -the leads didn't fit my neck bolts. ]

You hadda ask... ;-)

-- Gerald M. Payne (gmp@surferz.net), July 18, 2000.