Re: LED lights for filmmaking

From: Adam Aglionby (nws_at_capersville.co.uk)
Date: 10/21/04 

Date: Thu, 21 Oct 2004 01:31:41 +0100

Trimmed crosspost abit because server will think its spam...
Hi from sci.engr.lighting

"Daniel Kelly (AKA Jack)" <d.kellyNOSPAM@NOSPAM.ucl.ac.uk> wrote in message
news:cl5mu4$g2e$1@uns-a.ucl.ac.uk...
> Hello,
>
> I recently saw an advert for some LED lights for filmmaking. They looked
> perfect - very efficient, flicker-free, dimable from 0-100% etc. The
> problem is that they're extortionately priced. So now I want to make my
own
> LED lights for use on film...

Efficent ,er, um, see rhose MR16s your using at the moment, theyre probably
abit more efficient..

>
> Has anyone tried this? What should I be careful of? Can I vary the
colour
> temperature of the lights by pushing more or less current through the
LEDs?

Not really, whites because theri blue with a phosphor go a bit of angry blue
when you overdrive them though....

> Even better - does anyone know of any LED lights suitable for film that I
> could buy off the shelf here in the UK?

Sure I saw Kino Flo with some protype Luxeon LED film lights a while back,
but then they make fluro compact film lights which fro general light are
probably still a better bet.

> Here's my dream LED light:
>
> - dimmable from 0-100% with no change in colour temp (ultimately I'd like
to
> build in a remote control so I can change dim the light whilst I'm looking
> through the viewfinder on my camera)

Thats kind of doable , but current white LEDs are basic phosphor wise,with a
high colour temperature and not great Colour Rendering Index.
 RGB colour mixing does not give a good white , some units have started
using RGB and Amber to warm it up a bit.

> - cheap!

cheap or bright?
cannae have both

> - highly efficient

If you don`t need alot of light, say an LED macro ring it is efficient for
the purpose, as replacement Redhead, not yet.

> - stable and predictable colour temperature (it would be very cool if I
> could change the colour temp with a switch... my research into LEDs so far
> has hinted at the possibility of changing the colour temperature by
> increased in the current).

Going cooler CT wise in white,
but cooking LED in practice,
lowering efficiency, LEDs hit sweet spot at exceedingly low currents
Negative temp co-efficient means output goes down as heat goes up
Lowering lumen maintenace , cooked phosphors and LED dice put out less light
as they age, hard life will age them faster

> Please do let me know your thoughts - any leads you can give me will be
very
> well received

http://www.ledmuseum.org/

http://members.misty.com/don/

HTH
Adam

> Thanks,
> Jack
>
>
>

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