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Large LED bulbs for film lighting?

Discussion in 'Electronic Basics' started by lawpoop, Nov 21, 2005.

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  1. lawpoop

    lawpoop Guest

    Hey folks -

    I'm just getting into amatuer filmmaking. I took a class on low budget
    lighting and we spent a great deal of time talking about scouting
    locations properly for lighting. Two things you really have to worry
    about are power draw and heat. With movie lighting, it's easy to blow
    the circuits because several 1000 watt bulbs draw a lot of power, and
    then also they create a lot of heat. This makes it easy for them to
    melt plastic filters, their housing, even blow up the bulbs themselves.
    That's why you hear the director call "Lights! Camera! Action!" --
    because the lights are shutdown between takes to cool off.

    Of course, most of these problems are caused by the fact that these are
    incandescent bulbs, which waste a lot of energy as heat. A lot of these
    problems could be sovled by more effecient lighting techniques -- say
    LED bulbs.

    I know that LED bulbs are just now getting into home lighting, but I
    wonder why they aren't used in more film lighting. Film lights are
    expensive anyway, so I would guess LED lights could compete more
    effectively than in the home.

    Why are LEDs so small?

    Is it possible to get an LED bulb that kicks out 1000 watts of light,
    yet leave a small current and heat footprint?
  2. Andy Baxter

    Andy Baxter Guest

    lawpoop said:

    do multicoloured LED spotlights.
  3. Andy Baxter

    Andy Baxter Guest

    Andy Baxter said:
    P.S. they aren't on their site, but this was reported in the Sep 2003
    issue of electronics world, so maybe they still do them, or know someone
    who does.
  4. Bill Bowden

    Bill Bowden Guest

    I know that LED bulbs are just now getting into home lighting, but I
    I don't think you can get as good a white color with LEDs as with
    incandescents. White LEDs tend to be on the blueish side.

    Also, LEDs are less efficient than incandescents if operated at full
    power. To beat the efficiency of incandescents, I believe you need to
    reduce the power level quite a bit and add more LEDs to make up for the
    lost light.

  5. (snip)
    Most white LEDs are really blue LEDs thinly coated with a phosphor
    that absorbs blue light and emits yellow. The combination of blue
    (that gets past the phosphor) and yellow fool the eye into seeing
    roughly white. But there are big chunks of the visible spectrum
    missing, specifically green and red. So green or red objects (things
    that absorb blue and yellow, but reflect green or red light) look off
    color and dim when illuminated by white LEDs.
  6. As it turns out, a 1,000 watt incandescent puts out about 90-100 watts
    of light, maybe 500-600 watts of infrared and 300-400 or so watts of
    non-radiant heat (roughly).

    1,000 watts dumped into the most efficient LEDs out there, with those
    LEDs being run at full power, may get you 150 watts of visible light, not
    much infrared, and almost 850 watts on non-radiant heat (roughly).
    The ratio of heat to light actually increases due to lack of getting rid
    of heat as infrared. Just to make things worse, LEDs are less tolerant of
    high temperatures than incandescents.
    So, heat issues in fixtures are a reason to use incandescent lamps
    (including halogen lamps) over LED.

    But the main reason is that high power LEDs and high power LED cluster
    lamps are expensive. A 5-watt LED in small quantities costs around $30,

    There are LED stage and filming lights, but they are not yet in really
    widespread use.
    Advantages of LED stage and filming lights in general are, at least

    1. Ability to achieve some shades of colored light more efficiently than
    with incandescents and filters

    2. Ability to change color electrically

    3. Strobing capabilities that incandescents don't have

    But for high efficieny of producing light for filming, what they tend
    to use is special metal halide lamps such as HMI and the like.

    - Don Klipstein ()
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