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Flicker-Free HMI's


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Supposedly, yes. But I've gotten flicker on both straight tungsten and Kino's at strange fps/shutter angles, so there's really no telling. In ASC's manual there's a chart where one can kinda tell if you're in the danger zone. Might be useful in your instance.

Edited by AdamFrisch
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I had the pb : different answers about this same question. Here's the diagram in the asc manual. It's from the 80's edition. It may not take account of flicker free disposal, but if you're good for standard, you'll be good with flicker free. The problem is always, what happens if it doesn't work properly. I've seen non flicker free flickering at 25 fps 50 Hz. If a flicker free doesnt work properly, it may be better to respect the diagram...

 

Are you at 50 Hz or 60 Hz ?

 

http://l.andrieux.free.fr/hmi.htm

Edited by laurent.a
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Thanks for posting that chart Laurent. I got a look at one before the shoot. I was just a bit worried about flickering because I realized I've never overcranked with HMI's. I've always used tungsten units or straight sunlight before. I had a discussion with the Gaffer and he assured me that we would not get flicker with our ballasts, shooting at 32 or 48fps. We just wrapped today and the TK is set for Tuesday so I guess I'll know for sure then. There was really only one setup where the HMI was the main source of light anyway. The rest were mixed with sunlight.

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This is one those questions I should know the answer to but I don't.  Are square wave flicker-free ballast's flicker free at any speed?

 

Can I shoot at 32 and 48fps at 180 shutter and not worry?  I've been getting two different answers on this.

 

You will not get any flicker or flutter at any speed with a square wave HMI ballast when the unit is working properly. The only time you will get flicker or flutter with a square wave ballast is when you have a defective ballast, defective power source or a bad globe (usually old, to many hours).

 

I hope this helps,

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Gilbert,

 

Funny your signature is three times your post's size ! :)

 

You see, that's what I ment... How d'you know the ballast or lamp isn't working properly... before the daylies ! :D

 

I say that because a flickering-because-non-workering-properly one is not that rare, unfortunatly...

Edited by laurent.a
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Gilbert,

 

Funny your signature is three times your post's size !  :)

 

You see, that's what I ment... How d'you know the ballast or lamp isn't working properly... before the daylies ! :D

 

I say that because a flickering-because-non-workering-properly one is not that rare, unfortunatly...

 

Have it serviced to make sure it is working properly! They can tell the age of the globe and check the output power (square wave) of the ballast to make sure everything is working properly. Just like a car you want it serviced once in a while, correct?

 

By the way, I like my signature 3 times the post.

 

Best Regards,

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