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HMI flicker


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#1 Charles Haine

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Posted 23 October 2005 - 11:03 PM

I've never done it, but so many different texts warn me off shooting HMI's with a putt-putt generator that I've never even bothered.

However, the guy gaffing my next movie claims to have used a putt-putt with flicker-free HMIs (the pricier rental, but still cheaper than a synch movie genny), and that they were flicker-free. I've seen the footage, and there's no flicker, so I should believe him, but it goes against my gut.

Somewhere in the back of my head, I had it that all HMIs needed constant 50/60Hz, but flicker-free HMIs were good for more speeds, and maybe even speed ramps. Am I wrong? Should I just rent a putt-putt and flicker-free HMIs?

Addmittedly, he used the HMI for fill when he used it with the putt-putt, but you should still see flicker even in fill.

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#2 Kevin Zanit

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Posted 24 October 2005 - 12:13 AM

We have had this discussion fairly in depth before, so try a search.

I have used HMIs with a put put, and I don?t really recommend it. Theoretically it should work, but you need a perfectly maintained put put for that, and that is something hard to find.

I have found even then, I still had slight flicker.

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#3 Bob Hayes

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Posted 24 October 2005 - 02:14 AM

I?ve shot with a non sync put put and flicker free HMI?s and never had a problem. I?ve also shot 25 fps with a non sync generator and non flicker free HMI?s and didn?t have a flicker but I did have an in line frequency meter and an electrician adjusting the cycles by hand.
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#4 Charles Haine

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Posted 24 October 2005 - 09:11 AM

Sorry to repeat a thread, I just went back and read it.

What is a " inline sync meter," as mentioned in the last thread. What brand makes one, what price range would a rental be? If the genny doesn't have any control for the frequency, is there any point in getting one (I guess I could always fiddle with the throttle)?

thanks,
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#5 Kevin Zanit

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Posted 24 October 2005 - 01:28 PM

Many rental houses (for instance Wooden Nickel) will through in the inline meter when you rent the put-put.

It is a meter that tells you the Hz rate the generator is putting out, and you can adjust it tell you get as close to a solid 60 as possible (in the US).

You want to two-fer the output of the generator, one has the light you are powering, and one has your meter. That way you can measure the Hz rate while there is a load on the generator.


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#6 Gilbert

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Posted 24 October 2005 - 05:28 PM

I've never done it, but so many different texts warn me off shooting HMI's with a putt-putt generator that I've never even bothered.

chuck haine

You can use a putt-putt generator with an Electronic Ballast anytime, as long as the putt-putt generator meets the power output needed. For example: to run a 120vac 1200W HMI ELectronic Ballast you need a minumum of a 2400W generator. A putt-putt generator can fluctuate from 90vac to 130vac and the electronic ballast will regulate the output power to the lamp at the same voltage and current with no flicker.

Hope this helps,
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Visual Products

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The Slider

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Rig Wheels Passport

Gamma Ray Digital Inc

Aerial Filmworks

CineLab

Glidecam