Paul C. Buff, Inc. Technical Forum

I noticed reading an Alien Bees manual stating not to use fluorescent lights for modeling lights because they can create electrical noise. Is this statement is made for the sake of proper working of the flash unit, or are they considering interference to their radio controllers?

Other than negating the use of the dimmer or the ready light feature, I personally can't see how a fluorescent light can interfere with function of the flash unit, and it would be beneficial to run either a cooler light for the modeling light or a brighter one relative to wattage used.

Thanks for any info on this.

Most self contained, medium base compact fluorescent lights are designed to function at a particular input voltage, and if the voltage varies too much from optimal, they can self destruct, and possibly cause problems with the circuit that they are fed from. They are not simple resistance lights as are standard, and even halogen cycle bulbs (for the most part).

Fluorescent bulbs require much higher voltage than standard line voltage to fire, and once lit, they require external current limiting to keep them from becoming a pyrotechnic device. That is the function of a fluorescent ballast. Self contained bulbs of the type (CFL bulbs) have built in ballast devices, but they are not designed to modulate light output to varying input voltage. They are only designed to safely fire the bulb, and keep it stable within a narrow input voltage range.

The typical lights used as modeling lamps contain thin coils of tungsten wire that respond to applied voltage by getting hot enough to glow. They are tuned to glow at a certain color temp at a certain voltage. Exceed that voltage by too much of a margin, and the tungsten wire melts, resulting in an open circuit failure. As you lower the voltage, the light output, and color temp drops until there isn't enough voltage to make it glow anymore. A halogen light is pretty much the same, but at it's design output, it can be driven much brighter, and last much longer than a regular tungsten light, because of the magic of the "halogen cycle". Sweet. They make great modeling lights, as their relative output can be easily made proportionate to input voltage. Color temp will vary, but relative brightness is pretty reliable.

In essence, resistance lighting, and fluorescent lighting are really two different animals, but demand, combined with digital chip technology has made a few voltage dimable ballasts available for regular fluorescent tubes (about $95 ea, wholesale), and a few fairly expensive voltage dimable self contained spiral tube bulbs available as well. So far, they are still expensive, and not very linear in response. I'm sure that will change in time, but right now, the problem with using a CFL bulb as a modeling light goes far beyond simple RFI.

Voyager

Thanks for your reply. Well, as I mentioned in my first comment, if you use it strictly as either on or off, and not use it for ready light check (or the dimmer) , I don't see why a fluorescent lamp can't be used.

Having a 150 or higher wattage tungsten lamp generates a good amount of heat, especially if you're using several flash units. This is what primarily drew me to the potential use of a fluorescent lamp as a modeling light. It will run much cooler and can provide equivalent, and possibly greater, light output.

Mind you, I'm not hell bent on this, but if the flash circuit itself is not affected by using fluorescent lamps, and as long as you don't use the dimmer or use them as a ready light check, I don't see a reason why not to use them.

Thanks again for your reply.

I haven't seen an edison-based CFL of any appreciable equivalent wattage with a ballast small enough not to block the flash tube, even if there is no electronic disadvantage. There may be a flash unit designed in the future to accomodate such CFLs, but AlienBee isn't it, and nobody else is currently making one, either.

But if you're so sure that you won't take anyone else's answer as authoritative (not even the flash manufacturer's), you are certainly free to buy a selection of currently available CFLs and test your own theory.

Flourescent bulbs do introduce a lot of line noise, even if left at full power. Using a CFL can damage the dimmer circuit.

TS

Thanks for your replies. As I said, I'm not hell-bent on this, I just wanted to know SPECIFICALLY how or why a CFL bulb would damage or interfere with the function of the flash unit itself.

I am also interested. Would using a CFL damage the dimmer circuit even if you didn't use the dimmer or ready light check at all?

CF lamps are lousy for modeling lamps. Dimmable ones don't follow the same dimming curve as incandescence and won't be accurate. Plus, if they have any power, CF lamps are way big and won't give good modeling patterns.