# HMI / Tungsten

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Posted 13 March 2008 - 09:39 AM

Slight confusion today when discussing the pros of using HMIs.

I had always been of the opinion that an HMI would have a greater output per watt than a tungsten fixture.

i.e. a 2.5K HMI at 10ft distance = 800fc
a 2.5K Tungsten at 10ft distance = 600fc

assuming that the lens and dimensions of the fixture are identical.

Can anyone shed any light (pun intended) on this.

David
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### #2 Xavier Plaza

Xavier Plaza
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• Cinematographer

Posted 13 March 2008 - 11:12 AM

At Arri Photometric calculator you can make effective conclusion:

Tungsten:
Arrilite 2000K 10ft 295fc
Arri Fresnel 2000K(flood) 10ft 283fc

HMI
ArriSun 40/25(2.5K lamp - flood) 17ft 832fc
Arri Fresnel 2000K (flood) 10ft 412fc

You can see more difference when use Arrisun but at general terms always you get more "effective" power on HMI than tungsten. Tungsten lights use 70% of the power producing heat (correct me if i made a mistake).

Xavier Plaza
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### #3 James Brown

James Brown
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Posted 13 March 2008 - 03:54 PM

Hi,

"An HMI puts out about four times as much light as a tungsten light of the same wattage, 85-108 Lumens per watt of electricity, compared to 26 lumens per watt for tungsten bulbs.

James
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### #4 Michael Collier

Michael Collier
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Posted 13 March 2008 - 04:29 PM

Yeah its somewhere in the 4 to 5 times range. But thats only off the incident reading. If you take into account the color balance difference, then an HMI puts out more than 16 times the light of a CTB'ed tungstend (4 times the light, plus the 2 1/3 stop loss of CTB) or if you were to convert HMI to tungsten, then its somewhere around 8 times the light (2/3s stop loss, but I am too lazy to do the math, so I will round up to one stop and call it 8)

Edited by Michael Collier, 13 March 2008 - 04:32 PM.

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