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Topic: bulb substitutes - LED?

Jon Byler
Film Handler

Posts: 45
From: Auburn, AL, USA
Registered: Sep 2013

posted September 23, 2013 02:06 PM

Are there any out there? This seems like the ultimate way to replace old hard to find projector bulbs, but I'm not sure the power density is there yet. Lots of light, not much heat.

I was thinking about this for a way to replace the bulb in my bolex 18-5 when it eventually goes. it's too small for a standard MR16 bulb, and the smaller MR11's only seem to be available in about 30W size, which may be more than adequate moving from regular incandescent to halogen.

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Janice Glesser
Film Goddess

Posts: 3468
From: Sunnyvale, CA USA
Registered: Sep 2011

posted September 23, 2013 02:23 PM

Jon...you might want to pm Richard Bock from this forum. He sent his Bolex 18-5 somewhere to have it converted to run a lower cost halogen bulb.

--------------------
Janice

"I'm having a very good day!"
Richard Dreyfuss - Let It Ride (1989).

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Jon Byler
Film Handler

Posts: 45
From: Auburn, AL, USA
Registered: Sep 2013

posted September 23, 2013 02:35 PM

thanks,

I'll check with him to see what bulb it uses now. I'm still interested in the possibility of LEDs just out of general curiosity.

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Bill Brandenstein
Phenomenal Film Handler

Posts: 1632
From: California
Registered: Aug 2007

posted September 25, 2013 11:28 AM

Maybe for general illumination, like a threading bulb. But LED technology hasn't come to the point of being able to focus a massive amount of light on a tiny aperture. Halogens still win for best light for the lowest cost.

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Janice Glesser
Film Goddess

Posts: 3468
From: Sunnyvale, CA USA
Registered: Sep 2011

posted September 25, 2013 04:54 PM

LEDs are great for telecine work where low wattage is a must... but as Bill states not for image projection.

--------------------
Janice

"I'm having a very good day!"
Richard Dreyfuss - Let It Ride (1989).

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Pete Richards
Master Film Handler

Posts: 302
From: Australia
Registered: Sep 2010

posted September 25, 2013 05:33 PM

There are LED light sources for digital projectors available, it is conceivable that you could use one of those in a film projector, but it would take some work.
e.g. http://www.luminus.com/products/PT-121.html
http://au.mouser.com/ProductDetail/Luminus-Devices/PT-121-B-C11-EPA/?qs=AafiUGZxyHagkSb/QOrNew==

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Janice Glesser
Film Goddess

Posts: 3468
From: Sunnyvale, CA USA
Registered: Sep 2011

posted September 25, 2013 07:16 PM

You are correct Pete...but aren't those projector lamps much larger? Maybe someday a smaller higher wattage LED will be available to adapt to film projectors.

--------------------
Janice

"I'm having a very good day!"
Richard Dreyfuss - Let It Ride (1989).

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Bill Brandenstein
Phenomenal Film Handler

Posts: 1632
From: California
Registered: Aug 2007

posted September 26, 2013 11:47 PM

You would need a lens to focus the light onto the aperture. But the luminous flux rating might be comparable to 100w or 150w Halogen - if you can harvest the light, that is.

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Jon Byler
Film Handler

Posts: 45
From: Auburn, AL, USA
Registered: Sep 2013

posted September 27, 2013 12:02 AM

that is something I have been curious about. I've seen some led chips that claim to be good for well over 700 lumens. that's pretty bright if all of the light makes it though the gate.

is the ideal situation one where one has columnated light that is all getting through the aperature in the film gate? I imagine much of the light from a halogen is wasted bouncing around in there when you have upwards of a 2 inch reflector and an 8mm hole. What presents itself as the ideal projection light source in terms of beam and focus? does the light need to be focused on the film plane itself?

I'm having a hard time finding the answers to these questions...

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Bill Brandenstein
Phenomenal Film Handler

Posts: 1632
From: California
Registered: Aug 2007

posted September 28, 2013 11:07 PM

I'm no expert in this but think there's a great deal of wasted light in most any projector situation. Halogen bulbs lose a few percent through the dichroic reflector, more through the front angles untouched by the mirror, and around the top and bottom of the aperture. When you think of how much light comes from a 60w halogen car headlamp, where little light is wasted, you gotta think those projectors create a pretty inefficient situation!

But Jon, I'm sure you're right about one thing: yes, the light is focused on the film plane to whatever extent the technology permits. Halogen bulbs have a "working distance" for the mirror focus and you'll see that figure in bulb specifications.

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Jon Byler
Film Handler

Posts: 45
From: Auburn, AL, USA
Registered: Sep 2013

posted September 29, 2013 06:03 PM

Thanks for the reply. I'm looking at trying to use an led array that are all one chip, and perhaps slightly larger than the aperture diameter. These are available in various sizes and brightnesses, so something might work out. I have another idea too, that needs thinking through, though.

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Bill Brandenstein
Phenomenal Film Handler

Posts: 1632
From: California
Registered: Aug 2007

posted October 01, 2013 11:50 AM

You will keep us posted as to your findings, I hope! Thanks, Jon.

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