Help with Super8 projector lamp

[cosmovdo]

I'm upgrading a Super8 movies projector and want to change the light system. It's equipped with a MR16 100W 12V Halogen Cold light (5600ºK)
I need it to make a frame by frame transfer from film to video, so a 20W incadescent could do the job fine without burning the film if I adjust the camera exposure.
What's the chance to change the incandescent bulb for LEDs?
Thanks

 

[MikeRD03]

Hi cosmovdo,

I wouldn´t do that. Besides it may be possible a LED never render colors so good as a halogen can do. So for quality reason leave everything like it is.

cheers,
MikeRD03

 

[glire]

I do not agree. But maybe I wouldn't use a white LED.
I would use 5 colored LED: red, green, blue, cyan and yellow with the possibility to dim each LED independently.
Super8 use to be too reddish over time and halogen lamps are already too reddish. It should be better to compensate at the light source instead of using the video camera white balance and/or at post production assembly.

 

[ganled]

If you need color correction at a light source, use the correct filter for the application. Although halogen may not provide a truely even light, the problem with LEDs are that the light emitted may not be as flat or wide as an incandesent bulb. It is still possible to have spectrum peaks, non optimum colors, and contrast problems using multiple narrow colored LEDs. Also, make sure that you do not burn the film or destroy/damage anything else.

 

[cosmovdo]

Thanks for your help. I'll try using a MR16 3W Luxeon LED to get between 65 to 80 lumen (6000K). I'll put a Linos Photonic diffuser glass in front of the LED to avoid a hot spot.
Due the way I'll do transfers (frame by frame) I need to reduce the heat and light intensity, otherwise the frame will be overexposed or the film burned.
I'll try this way, the whole changes are reversible so I can go back safely.
Thanks again and any comment is welcome for sure.

 

[glire]

A bit OT, but what super8 projector and video camera do you use ? And how do you synchronize each film frame with the video capture ?
Thanks

 

[cosmovdo]

I'm using an Eumig Mark 610 which runs smoothly at 3 frames per second. It's modified with a roller microswitch that generate a pulse each time that a frame is exposed on the gate.
This pulse is sended to a modified mouse that trigger a capture software on a computer, so the only requirement for the camera is a good optical zoom.
The technology is not mine. The only change I want to make is subtitute a 20 watts bulb for a LED in order to reduce the heat stress on the film.

 

[SemiMan]

I suspect if you add another hot-mirror that reflects the IR, you may reduce the heat stress a lot on the film.

Though I love LEDS, I tend to agree with the comments regarding color. The holes in the color spectrum of white LEDS will be hard to correct for. If you want to write custom software to apply a correction you could make it work, but I would guess standard s/w will not be sophisticated enough as it pretty much assumes flat spectrum light sources.

The other issue you are going to run into is focus. The optical system in the projector is designed for that halogen bulb. The MR16 LED is not even remotely the same. Odds are you will have a hard time getting even light consistency.

Let us know how it goes.

Semiman