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HMI flicker High speed cam


fred Austin

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Hi there , i'm French gaffer looking for any kind of smart advises

that could help me -and others- to solve(?!)or at least find a way

to get rid of the kind of bad surprises we might have encountered

when shooting with multiple hmi heads at high speed-above 500fs.

I know about Lumynis , i'm looking for some kind of gaffer tricks..!

Thanks for u'r help,and make yourself comfortable to shoot in Paris

nice city that loves cinema,u might even find useful techs with many

surprising skills!! Cheers

Fred Austin

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gaffers are the cameraman's best friend! i mean literally! My closest relationship on set is with the director and gaffer in that order.

there skill and inventiveness is what makes what we do still a craft!

I suspect if you were having flicker problems with multiple HMI's there were different ballasts being used.

also if your shooting above 500fps you need really big lights.

 

The gaffer tricks I will leave to the gaffers!

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  • 2 weeks later...

According to Harry Box, you can create a single flicker free light source (even with magnetic ballasts) with one light on each phase of electricity. As each will be on a different part of the sine wave the overall light will appear to be flicker free.

 

One caveat: I have never tried this so if you do try it, test it first. I also don't have experience with extremely high frame rates and the problems inherent with those rates. I'm just reitorating what Harry Box mentions in his book. So test test test. Maybe tungsten is better than this method as others mentioned.

 

So when in doubt. do a test. Did I say that enough?

 

Best

 

Tim

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Thanks Mitch,Tim,Kieran, do you agree with this ...http://www.pirate.co.uk/en/node/266 ?

f.

 

Hi,

 

Not entirely, I was shooting 2000 fps yeaterday table top, I chose 10Ks tungsten over HMI's as i can dim the tungsten so overall there is way less heat than with HMI that cant be turned off between takes. Lights on for 30 seconds , dim lights to 10% set up for next take etc. The studio was rather cold so I had to wear a ski jacket!

 

Stephen

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Hi,

 

Not entirely, I was shooting 2000 fps yeaterday table top, I chose 10Ks tungsten over HMI's as i can dim the tungsten so overall there is way less heat than with HMI that cant be turned off between takes. Lights on for 30 seconds , dim lights to 10% set up for next take etc. The studio was rather cold so I had to wear a ski jacket!

 

Stephen

 

Food? They guys I know who do food spots utilize the dimmer pack method too. And a lot of heat shield. Makes it more comfortable for the humans too.

 

Best

 

Tim

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  • 3 years later...

We've just finished high speed shooting yesterday. Finally I can't agree with Mitch. Arri high speed ballasts works great for high speed up to 2500fps.

Here are the lamps I've used: Mole Richardson 24K daylite fresnel with 300Hz powergems ballast, 3x M90 ARRI 9KW with 1000Hz arri ballasts, 9KW alpha K5600 with powergems 1000Hz ballast, 1.6KW Joker bug with powergems 1000Hz ballast, 2x ARRI M8 with high speed ballasts (1000Hz). The only lamps that works with standard 75Hz ballasts were ARRI M90s. They can be used up to 2000fps without any sign of flickering. Shooting has been made with two phantom cameras.

I'll post some links to videos later.

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