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Old November 5th, 2006, 08:41 AM   #1
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what is the different between Fresnel light and daylight?

what is the point to buy light like Arri HIM daylight 2500W for about 9000USD ? what is the different between Fresnel light with daylight filter and HMI lighting kit?
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Old November 5th, 2006, 10:17 AM   #2
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Fresnel is a lens that you can find on either tungsten or HMI lights. The HMI lights are much more efficient than tungsten lights that have daylight colour correction filters. A 2500W HMI produces around one and half times the light output of a 10K tungsten light with a daylight filter. Basically you're reducing your power requirements and producing a lot less heat on set because you're not using a hot tungsten lamp.

If you're only occasionally using HMIs, it's much better to rent.
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Old November 5th, 2006, 10:42 AM   #3
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Thank u so much Brian for this information i plan to get 2500K HMI light so i need also some information about different between Electronic Ballast and Magnetic ballast ,look is to far in price between to this ballast,think u agean 4 this help.
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Old November 5th, 2006, 12:09 PM   #4
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Magnetic ballasts for HMIs are VERY heavy because they have huge heavy magnets inside as part of the design. It's an older design, and the light also flickers with the AC current at 60 or 50hz, depending on your mains power. This can require special care when shooting film, especially slow-motion.

Electronic ballasts are the "new school", and as a result are much more expensive. They are generally much lighter and smaller, and the flicker in the light is modified so it happens at a much higher frequency, so high it is inconsequential for any type of camera/filming speed.
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Old November 5th, 2006, 01:00 PM   #5
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With the magnetic ballast you need to use the correct shutter setting when shooting 24P video, since the effect is the same as shooting film.
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Old November 5th, 2006, 05:36 PM   #6
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Quote:
Originally Posted by Nate Weaver
Electronic ballasts are the "new school", and as a result are much more expensive. They are generally much lighter and smaller, and the flicker in the light is modified so it happens at a much higher frequency, so high it is inconsequential for any type of camera/filming speed.
Ditto for Fluorescents. Always go with high freq electronic ballasts if you can.
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Old November 5th, 2006, 07:09 PM   #7
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Quote:
Originally Posted by Nate Weaver
Magnetic ballasts for HMIs are VERY heavy because they have huge heavy magnets inside as part of the design.
Nate, FYI, There are no magnets in magnetic ballasts. They are called that because they use inductors, which operate on electroMAGNETIC principles. The weight is in the steel (non-magentized) core and windings of the inductors. Electronic ballasts often use inductors too, but because of the high frequencies of operation, the inductors can be much much smaller and lighter.
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Old November 5th, 2006, 07:22 PM   #8
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Aha. I knew it was big hunks of metal with tons of windings around them, guess I always assumed the metal being magnetic was part of the deal somehow.

But I knew that a simple inductor is just metal and a winding...

Thanks!
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