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HMI noise problem


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#1 hollyrandall

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Posted 26 June 2012 - 10:33 AM

Hi everyone- first time posting here and I hope this is the right section to post this question in. I have problems with HMIs sometimes making a loud buzzing noise when I'm shooting. Sometimes when I rent lights they are quiet at the beginning of the day and then towards the end I get a loud buzzing noise that drives me nuts. I've been using HMIs on and off for a while and I still have issues. The rental place had no advice for me, and even seemed to act surprised that I was encountering this problem. I've given up on getting silent lights so I was wondering if there is some kind of simple sound mixer I can run my audio through while filming. I can't afford a proper sound guy so that's not an option. I've used various sound filtering programs in post, such as Sound Soap but sometimes to eliminate the hum I'm forced to settle for an echo-y sounding audio. Obviously this situation is worse in small rooms. I'm a photographer by trade for the most part but as I move into shooting more video I'm really looking to perfect my technique. Any advice would be much appreciated!
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#2 Phil Rhodes

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Posted 27 June 2012 - 08:54 AM

Short answer - yeah, it happens. It's a bit like the fluorescent lighting manufacturers who claim you can dim their stuff all the way down to zero - you can't, but it doesn't stop them making the claim. Similarly, lots of people claim that HMIs are silent, which is sometimes true but not always.

Is the noise coming from the lamp head or the ballast? In some cases, if you switch a modern electronic ballast to flicker-free mode, it will cause the lamp head to emit a sort of hissing, singing silvery sort of sound, but you can avoid that by only using flicker-free mode when you're shooting off speed (and therefore less likely to need sync sound in the first place). Of course, you should carefully evaluate whether any flicker or rolling-bar problems are caused by any changes you make to lighting settings.

Otherwise, yes, some HMIs hum either from the ballast, the lamp head, or both. Good quality modern ones shouldn't, and extreme cases may mean the thing needs servicing. Maybe you could get the rental place to run one up for an hour or so, in your presence.

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#3 Phil Rhodes

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Posted 27 June 2012 - 08:57 AM

Short answer - yeah, it happens. It's a bit like the fluorescent lighting manufacturers who claim you can dim their stuff all the way down to zero - you can't, but it doesn't stop them making the claim. Similarly, lots of people claim that HMIs are silent, which is sometimes true but not always.

Is the noise coming from the lamp head or the ballast? In some cases, if you switch a modern electronic ballast to flicker-free mode, it will cause the lamp head to emit a sort of hissing, singing silvery sort of sound, but you can avoid that by only using flicker-free mode when you're shooting off speed (and therefore less likely to need sync sound in the first place). Of course, you should carefully evaluate whether any flicker or rolling-bar problems are caused by any changes you make to lighting settings.

Otherwise, yes, some HMIs hum either from the ballast, the lamp head, or both. Good quality modern ones shouldn't, and extreme cases may mean the thing needs servicing. Maybe you could get the rental place to run one up for an hour or so, in your presence.

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Glidecam

Broadcast Solutions Inc

Aerial Filmworks

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Technodolly

Metropolis Post

FJS International, LLC

Ritter Battery

Rig Wheels Passport

CineLab

Gamma Ray Digital Inc

Tai Audio

CineTape

Media Blackout - Custom Cables and AKS

Paralinx LLC

rebotnix Technologies

Willys Widgets