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HMI Output


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#1 Nick Centera

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Posted 06 March 2010 - 04:06 PM

Hey, I was wondering if the output from an HMI source is great then a tungsten source of relatively the same level. For example, if you had a 2k HMI and a 2k fresnel, would the footcandles be the same? Or do HMIs have a greater output? Thank you

Nick
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#2 Matthew Parnell

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Posted 07 March 2010 - 08:09 AM

Generally the HMI is going to be a lot brighter. But it is also going to be daylight balanced.

As to how much brighter, you will have to look up some photometric charts to find out. There are many different types of HMI gear, and that all plays a part, as well as age, state of repair, Fresnel vs Par, lenses, etc.
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#3 David Mullen ASC

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Posted 07 March 2010 - 09:34 AM

Generally, an HMI of the same wattage is twice as bright / energy efficient as a tungsten lamp but it's hard to compare photometric data since there aren't matching units -- there is no 2K fresnel HMI, for example. There is a 5K fresnel tungsten and a 6K fresnel HMI, a 10K fresnel tungsten and a 12K fresnel HMI, etc.

However, if you think this means it's better to just gel HMI's to 3200K, think again -- the color is a bit odd when you do that.
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#4 Nick Centera

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Posted 08 March 2010 - 01:23 AM

However, if you think this means it's better to just gel HMI's to 3200K, think again -- the color is a bit odd when you do that.
[/quote]

I see. I have heard of people using HMIs a lot for interior lighting and studio light, and as you say you, just because you gel an HIM doesn't mean it will look correct, then why is it that people choose to use them? If shooting on tungsten balanced stock, whats the benefit for using the HMIs when you can get rid of the light loss of gels and extra equipment of ballasts? I guess what I am saying is, what is the advantage of using HMIs on nights and interiors on T balanced film?
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#5 Satsuki Murashige

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Posted 08 March 2010 - 01:51 AM

The greater output per watt is the main advantage. You can place the lamp farther away and get the same stop, rendering more natural shadows. It may also mean less relighting between setups, since the light is already in an ideal place. Or you can bounce it or diffuse it and still get enough stop. I think tungsten is still the standard for studio though.
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