Flicker Free HMI ballasts and generators

Jody Lipes · April 12, 2004

Is flicker a risk if you are combining a flicker free ballast HMI with a generator which is not crystal sync, and shooting at an appropriate frame rate (24 or 48 fps)?

My cinematography teacher, Michael Carmine, told me that I need a crystal sync generator whenever shooting with HMI's. I'm not sure if he meant without a flicker free ballast, or with one.

It seems like all of the rental houses in NYC think that I am crazy when I ask for small crystal generators.

I need to use 2K generators for decible level and cost. If I do need a crystal generator, do they make them that small?

Mitch Gross · April 12, 2004

You can get a little genny and hook up a flicker-free ballast, but I wouldn't reccomend it. There's a chance it will begin to flicker as the ballast is taxed by the uneven power and it certainly will shorten the life of the gear. Most rental houses won't give you the gear if they know you plan to use it this way and if you blow an HMI bulb it will be a very expensive replacement.

You can get 5000 watt crystal gennies from CECO or Hotlights for about $165/day. They're pretty hefty though: you'll need a van and four strong people to lift it in. When I have to compare it in size to something that a New York film student would recognize, I usually refer to the grocery carts that D'Agostinos and other supermarkets use to deliver groceries to people's homes. It's like an office desk with wheels.

Jody Lipes · April 13, 2004

so i do need a crystal generator with a flicker free ballast, and they don't make them as small as two K?

Kevin Zanit · April 13, 2004

The smallest I have seen is 5000 watt converted Honda genies. The company that does the conversions is Young Generators (there are also others that do conversion as well, but I cant remember their name). It includes putting the genie in a nice rolling chaise, crystal speed control, 60 AMP bates connector, and also give you the ability to switch between parallel windings (one 45A 120V circuit) or series (two 20A 120V, one 45A 240V circuit), and a fuel pump.

Kevin Zanit

Mitch Gross · April 13, 2004

so i do need a crystal generator with a flicker free ballast, and they don't make them as small as two K?

As I said, I've seen others use non-crystal gennies with flicker-free ballasts but I wouldn't reccomend it. You cannot be assured of zero flicker and you might end up with costly damage to the equipment. The smallest crystal genny I know of is 5000w. Non-crystal are available much smaller.

Why are you so afraid of a crystal generator? It's just like a big lawn mower and one will be enough to run two or even three small HMIs.

Jody Lipes · April 14, 2004

All of the rental houses are saying you don't need crystal. I know it has probobly been a while since you have been in a similar situation, but it is hard to argue with these guys when you are young, and have different information than they are acustomed to.

Affraid is an interesting choice of words, however, I have budget concerns when shooting a student film which don't allow for all of the distro gear and extentions needed to get something that loud far enough away. I also don't have the man power in my lighting crew to move something of that size.

I was also told today by an nyc rental house that a 2k generator won't hold a 1.2K HMI. It is hard for me to know whether they are trying to take advantage of me, or whether I actually do need a larger generator. This information goes against everything I have learned, because even with the amprage required for the initial strike, the .8K should be plenty of room powerwise. Am I being swindled, or is 2K too small for a 1200 HMI?

Kevin Zanit · April 14, 2004

Out of practice I would not run a 1.2k HMI on a 2k geni. As you said, the intial striking of the globe will be very taxing on the geni. You will need to run quite a distance of cable that will also build up a lot of resistance.

In practice you can use normal extension cords (orange) for your purposes. These are cheap, and avaible. You are in NY, its noisy at it is, if you can run the geni a few hundred feet away, around a corner there is no way you would ever hear the geni.

If you can afford HMIs I dont see why you would not want to spring for the right power source for the job.

We all have to jugle budget limits, not just students. So we all can relate to your plight, trust me.

Everyone here is advising you to not bull poop around with the wrong power, just spring for a crystal 5k Honda. There are so many other things that can go wrong, why risk it?

Kevin Zanit

Mitch Gross · April 14, 2004

Well if the rental house says go ahead then I wouldn't worry about damaging the gear! I also think the odds are against you having flicker but I was just being conservative. But the 2k genny not running a 1.2k HMI is a believable issue. I've seen 1.2k HMIs trip 15amp circuits plenty of times. And a 2k genny is probably not a "true" 2k, meaning that it likely has a 15amp circuit breaker on it and is really only meant to run up to 2k for brief periods. Run a bit of cable extension to get the genny far from the light for noise and the line resistance will cause the breaker to quickly trip.

Here's an easy test: go over to CECO, Xeno Lights, Hotlights or wherever and try running one of their HMIs on one of their 2k gennies for a while and see what happens.

If you want to save money, try getting a non-flickerfree ballast (cheaper) to offset the cost of the more expensive generator. Or see if there is a place that you can pay to plug in your light, which will invariably turn out to be cheaper than renting and dealing with a generator anyway. Or if you don't need to run it for too long you could even look into battery-powered options. Handheld Films has some battery-powered HMI options of greater size than you might think. The higher rental cost may still be cheaper than the generator cost, but you will have limited time on the light.