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Color temperature of halogen lamp vs intensity

  1. Dec 23, 2011 #1
    Hey there!

    I'm doing some experimental work at a microscope, where the lamp in use is stated to be
    "Lamp bulb: 12 V DC, 100 W halogen lamp bulb (Osram HLX 64623 or Phillips 7724)."

    I'm doing some calculations to analyse some of my images, and in there I need the intensity distribution of the lamp.

    The color temperature of the lamp is stated as 3200k, and I can just plug that into a black-body distribution.

    HOWEVER, how does the colortemperature of a halogen lamp change when the intensity changes? I operate the microscope at the lowest intensity it allows, so I guess the 3200k is no longer appropriate.

    I know that a normal light bulb seems "warmer", when you turn down the power, but how does this translate to a halogen lamp?

    Best Regards, and happy holidays! =)
  2. jcsd
  3. Dec 23, 2011 #2


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    Staff: Mentor

    A halogen lamp uses a tungsten filament just the same as the older lamp type, but the halogen gas allows the filament to operate at a hotter temperature, so this means that it glows whiter (in the same way that hotter stars glow whiter, even bluish.) If you dim it by dropping the voltage, I expect its illumination will become yellower in the much same way as that of the ordinary lamp. The reduced operating temperature will give it a much longer life before it burns out, though. :smile:

    I reckon manufacturers would be able to supply the color temperature of their lamps, for reduced operating voltages. Have you tried googling?
  4. Dec 23, 2011 #3


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    Science Advisor
    Gold Member
    2017 Award

    Can you get a neutral density filter to fit the lamp housing? That could give you the right colour temperature and the right intensity too.
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