Re: Large LED bulbs for film lighting?

In <1132613969.913567.88380@xxxxxxxxxxxxxxxxxxxxxxxxxxxx>, lawpoop wrote:
>
>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?

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,
give-or-take.

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
theoretically:

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 (don@xxxxxxxxx)
.

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