Some questions and a crazy idea for continuous lighting film portraits

[dsiglin]

First my main question:


I've become comfortable using speedlights for digital portraits, but I do not even want to think about using them for film portraits, for a variety of reasons. Is my only option for mobile continuous lighting going to be an expensive mobile AC power pack?


Second my crazy idea:


After reading about some LED bulbs with fairly good spectrum I thought perhaps it would be possible to build something like the Rosco Litepad and power it from batteries much like those LED banks you see for video use. The idea being to diffuse the light through semi opaque plexiglass creating a evenly glowing panel. I have some experience making similar panels for computer case lighting but there are more variables to account for with portrait lighting. Or perhaps something more powerful like this.


Addendum:

Perhaps a car battery and an inverter like this one to drive those bulbs or CFL?

 

[Derrel]

Those Cree bulbs look intriguing. I think you could make something that might work.

 

[dsiglin]

Well then my only option is to experiment. For the good of us all.

I had a lengthy conversation with a coworker about this and he pointed out it would be more efficient to run the LEDs off 12v since they are in fact direct current, unlike tungsten bulbs or CFLs, hence the need for an inverter. The other question then is how many lumens do I need to put out? Turns out a 100W incandescent light bulb puts out around 1500 lumens. So to get 500w equivalent light we would need 7500 lumens. That's actually quite easy to achieve if you slap two of these in.

I guess the other question is what color temp would be best? Something more warm or something similar to the sun?

Ok well once I know more (after I've tested) I'll report back what I've found.

 

[Braineack]

Wouldn't a litepad be much easier to make using this: High Power 50W LED Flood Light Fixture | High Power LED Spot/Flood Lighting and Portable LED Work Light | Work & Off-Road Lights | Super Bright LEDs



???


65w off a 12v battery that's rated at 60aH would be just over 5 hours of use. Although you'd still need an inverter to bring the voltage up, since it looks like it runs on AC.

 

[dsiglin]

That is definitely a tempting option.

The more I think this over I see the benefit of being able to use readily available light modifiers like softboxes or barn doors. Someone had a similar idea but for monolights and speedlights:
Super Easy DIY Rechargeable Battery Power Pack For Event Photographers | DIYPhotography.net

 

[dsiglin]

Yes it is. Based on my tests and Neil vN's article I'd say you would want AT LEAST 1200 watts of directional incandescent light, or about 440 watts of directional fluorescent light.

The new Cree LEDs look promising but aren't high enough watts to be practical right now. You can get 1200 incandescent watts by using eight fluorescent bulbs. Those LED bulbs are slightly more efficient but only 60w incandescent equivalent. You would need 20 of them. :/