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Discussion Starter · #1 ·
Why does the JVC G15 require a 420 watt Xenon lamp to achieve the same light output as the Hitachi with a 220 watt UHP lamp. Are the Hitachi panels more reflective? Is the optical path more efficient on the Hitachi?


Don
 

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Attached is a cartoon that depicts some of the issues when using lumen to describe lamps.

Lumens are defined as light flux at 540nM. Pretend that the two graphs attached are real light sources. The graph on the left will describe a lamp that puts out a lot of lumens, and consumes little power. The graph on the right describes a lamp that has low lumens, but consume more power to do so. Also note, that the lamp on the right puts out a much wider spectrum of light.
 

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Quote:
Originally posted by noah katz
Hi Don,


Xenon lamps inherently give less lumen per W of power input.
A lot of the wattage is wasted producing heat instead of light. However what little light is produced per watt is much whiter than the red tented UHPs.
 

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" red tented UHPs."


UHP's are blue/green tinted and weak on reds. Xenon has more red, which brings it closer to 6500K than UHP.
 

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Quote:
Originally posted by Don Giberson
Why does the JVC G15 require a 420 watt Xenon lamp to achieve the same light output as the Hitachi with a 220 watt UHP lamp. Are the Hitachi panels more reflective? Is the optical path more efficient on the Hitachi?


Don
Don,


It's not the panels - but the lamp itself.


UHPs give you more lumens per watt - but at a color temperature of 8000 K - which is too blue.


Xenon gives you less light per watt - but what it does output is close to the ideal color temperature of 6500 K.


Nothing surprising here. Lasers output very pure color coherent light - but they are not as efficient as white

lamps. Quality and efficiency do not always go hand-in-hand. In fact, they are often anti-correlated.


Dr. Gregory Greenman

Physicist
 

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Discussion Starter · #9 ·
Thanks for the clarification. I never knew that the wattage specification on a lamp was rated power consumption, not output.


Don
 

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Quote:
Originally posted by noah katz
" red tented UHPs."


UHP's are blue/green tinted and weak on reds. Xenon has more red, which brings it closer to 6500K than UHP.
Sorry had it backwards. Warm is red and a lower temperature. Cool is blue and a higher temperature. It is always confusing with warm being a lower temp and cool a higher temp.
 
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