Lighting for live event: HMI(hard)+Fluorescent(soft)

T

Trey T

Active member
Lighting for live event: HMI(hard)+ Fluorescent(soft)

Hey everyone, I would like get some idea about shooting under both HMI and compact fluorescent. I searched the forum but couldn't conclude much.

will I run into trouble w/ pulsing/flickering when shooting under both? I googled some stuff about compact flruorescent and HMI, and it say that I wont get the flickering effect of the ballasts. Now, does it apply to all HMI and CFL?

are there specific type of HMI bulb or CFL bulb I'm suppose to use?
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Also, I would like to know is it worth the trouble to retrofit HMI into incandescent-type housing? .... like this guy

Can someone recommend me a housing similar size to the link above? I would like to purchase some used ones on ebay.

thanks,
 
Output frequency and electronic ballasts... its all about that.

Magnetic ballasts of either fluorescent or metal halide / hmi types or cheap electronic ballasts of either type may have issues with flicker at some frame rates / shutter speeds. You have to do tests to see if there will be an issue or not because in many cases you won't know what the output frequency is of ballasts in practical fixtures in places you are shooting. Therefore, test and be sure.

As for DIY fresnels using metal halide, of course you can do that, I showed how people can do that for under $500 back in 2007 in some articles in my blog, then we came out with a line of fresnels to prove it. The CDM 150 is still under $500.
 
thanks for the reply, richard.

the frequency that you're speaking of, what is the numerical value that I am looking for?

the reason why i want to retrofit bc couple friends of mine do have different power-rating electronic ballast for metal halide that I can use. these were used for fish aquarium. I just need a proper base and corresponding/matching bulb. but i will try diff thread about your tutorial.
 
Its different for fluorescent and metal halide. Actually a bit more complex for metal halide. The output frequency on the ballasts available for many flos these days is anywhere between 10,000 hz and 50,000 hz and that would never give flicker at just about any normal FPS or shutter you can imagine. Even some slo mo type stuff would be fine.

HMI bulbs can't be driven that high. You'll commonly see them driven from between whatever the line voltage of a country is (50 or 60 hz) and something like about 400 hz. The 50 or 60 hz magnetic ballasts will have some flicker of course at some common FPS and shutter speds. The issue with driving at higher frequencies is they tend to oscillate and "sing" the higher they are driven so 100 to 200 hz is a common range for those electronic hmi ballasts. And, thats enough to get you out of trouble actually so you can see that 10,000 to 50,000 hz on fluorescents is actually overkill but its a pity we can't do that on an HMI bulb to have that kind of overkill.

There are metal halide bulbs that can be driven higher and some are even in the aquarium DIY world that can be. Its totally an experimentation thing as to whether it will work well for video or not from the standpoint of noise (fan on ballast, bulb that "sings", ignitor that "sings", etc.). In addition, the manufacturers rarely quote the output frequency so you have to specially contact them to find out the frequency they drive them at.

We have a whole closet full of ballasts from our experimentation that weren't suitable before we got to the ones we actually sell in our pro fixtures.

Its not an easy subject to play with for sure and takes a lot of determination to try something new that isn't proven out yet.
 
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