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HMI flicker High speed cam


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#1 fred Austin

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Posted 11 February 2011 - 12:53 PM

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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#2 Kieran Scannell

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Posted 11 February 2011 - 05:10 PM

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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#3 Mitch Gross

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Posted 13 February 2011 - 02:34 AM

The only "trick" is that one should not use HMIs when shooting very high frame rates due to Arc Wander. Large tungsten fixtures (5000w and up) are recommended.
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#4 fred Austin

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Posted 13 February 2011 - 04:05 PM

Ok,merçi les gars.Thanks,so I keep on saying DC supply/Sun/Luck...
obviously there'r no more tricks on your side of the Atlantic than
on mine,so i keep on digging..n'thinking! cheers
Fred Austin
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#5 timHealy

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Posted 25 February 2011 - 10:38 AM

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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#6 Mitch Gross

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Posted 25 February 2011 - 12:03 PM

Harry is talking about normal frame rate shooting, not high speed. It's a very different animal.
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#7 fred Austin

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Posted 25 February 2011 - 03:26 PM

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

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Posted 25 February 2011 - 03:47 PM

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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#9 fred Austin

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Posted 26 February 2011 - 02:42 AM

Have u ever used these: http://www.arri.com/...Hash=cbf6c864da above 1000fps ? f.
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#10 timHealy

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Posted 26 February 2011 - 08:50 AM

Harry is talking about normal frame rate shooting, not high speed. It's a very different animal.


hence my caveat

best

Tim
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#11 timHealy

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Posted 26 February 2011 - 08:53 AM

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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#12 Mitch Gross

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Posted 26 February 2011 - 11:25 PM

We have tested the ARRI High Speed HMI ballasts and definitely got flicker.
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#13 Tomas M

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Posted 06 August 2014 - 02:02 AM

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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#14 Brian Drysdale

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Posted 06 August 2014 - 02:24 AM

You should note that you need to use your full real name, it's one the forum rules. You should contact Tim Tyler, the site owner to make the change, since you can no longer do this yourself.


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