Jump to content


Photo

Blowing a light bulb


  • Please log in to reply
10 replies to this topic

#1 Vincent Sweeney

Vincent Sweeney
  • Sustaining Members
  • 686 posts
  • Director
  • LA at the moment.

Posted 06 July 2010 - 05:19 AM

Anyone ever pulled off forcing a standard household tungsten light bulb to go out on command? I doubt I'd be successful at making a hole at the base to release vacuum so the filament will naturally pop so I was thinking of a lower voltage bulb on a high-volt circuit.
  • 0

#2 Rob Vogt

Rob Vogt
  • Basic Members
  • PipPipPipPip
  • 437 posts
  • Other
  • New York

Posted 06 July 2010 - 07:27 AM

Why not just turn it off?
  • 0

#3 JD Hartman

JD Hartman
  • Basic Members
  • PipPipPipPip
  • 1690 posts
  • Gaffer
  • Edison, N.J. U.S.A.

Posted 06 July 2010 - 11:38 AM

What sort of look or effect are you expecting? Some sort of dazzling flash? The glass envelope isn't going to burst (without assistance) if that's what you want. In films, where strings of household bulbs go out in a blaze of glory, it usually looks eminently fake.
  • 0

#4 Brian Drysdale

Brian Drysdale
  • Basic Members
  • PipPipPipPip
  • 5070 posts
  • Cinematographer

Posted 06 July 2010 - 12:49 PM

Most people just switch them off, the usual problem is syncing the film lights to go off with the ceiling light, table lamps are no problem.
  • 0

#5 Vincent Sweeney

Vincent Sweeney
  • Sustaining Members
  • 686 posts
  • Director
  • LA at the moment.

Posted 06 July 2010 - 03:51 PM

I guess assuming I sort of went through the obvious solutions and have some idea of what I want is asking too much. ;)

I probably should have stated it more like this:

I need to get a bulb to "naturally" pop when turned on. The shot will have the bulb in it. The effect of a bulb actually popping is very different than turning it off. The bulb is the key source and the frame will go mostly black other than some 3 or 4-stop-under background ambient light.

And by "pop" or "blow" I mean that the filament goes to super white then breaks, like what happens when they reach the end of their life or lose vacuum suddenly.

Using a 12V "RV" bulb is one idea that came to mind as they have a standard base and look just like a normal bulb. A sudden 120v surge may do it. Something like this: http://www.elightbul...tage-Light-Bulb
  • 0

#6 David Mullen ASC

David Mullen ASC
  • Sustaining Members
  • 19769 posts
  • Cinematographer
  • Los Angeles

Posted 06 July 2010 - 04:34 PM

Yes, over-volting the light usually causes it to pop. Not sure if running the bulb through a variac and just cranking it to max is enough to cause an ordinary light bulb to pop so this notion of using a bulb rated for a lower voltage sounds good.
  • 0

#7 JD Hartman

JD Hartman
  • Basic Members
  • PipPipPipPip
  • 1690 posts
  • Gaffer
  • Edison, N.J. U.S.A.

Posted 06 July 2010 - 06:21 PM

And by "pop" or "blow" I mean that the filament goes to super white then breaks, like what happens when they reach the end of their life or lose vacuum suddenly.

Using a 12V "RV" bulb is one idea that came to mind as they have a standard base and look just like a normal bulb. A sudden 120v surge may do it. Something like this: http://www.elightbul...tage-Light-Bulb


You'll probably have to experiment a little. With a variac dialed all the way down to 12 volts, it might require quite a voltage increase to burn out the filament. The effect could appear, too slow. You may want to consider two 12 bulbs, wired in series, one on-screen, one off-screen, running off the variac at 24 volts, with a switch to bypass the off-screen bulb. That should produce a bright and predicable blown bulb.
  • 0

#8 Vincent Sweeney

Vincent Sweeney
  • Sustaining Members
  • 686 posts
  • Director
  • LA at the moment.

Posted 07 July 2010 - 12:28 AM

I'm curious why you wouldn't just apply a full 120v to the bulb at the time needed to pop it?

Thanks. I'm getting with the gaffer Thursday to test it out. I'll follow up here.
  • 0

#9 JD Hartman

JD Hartman
  • Basic Members
  • PipPipPipPip
  • 1690 posts
  • Gaffer
  • Edison, N.J. U.S.A.

Posted 07 July 2010 - 09:47 AM

From you original inquiry, it seemed that you want the bulb "on" and visible in the shot, followed by the sequence (however brief) of the filament going "super nova" and burning out. I didn't interpret it as the desire to have the bulb switched on and instantly "blow". If that's want you want, a 12v globe on 120vac should flash and expire predictably.
  • 0

#10 timHealy

timHealy
  • Basic Members
  • PipPipPipPip
  • 1252 posts
  • Other
  • New York

Posted 10 July 2010 - 10:32 PM

using a variac may not be enough to get a 120 volt bulb to pop. It could work but a variac would get it up to 140v. A household bulb may be able to take it. wiring it to 220 volt would certainly do the trick though.

best

Tim
  • 0

#11 Vincent Sweeney

Vincent Sweeney
  • Sustaining Members
  • 686 posts
  • Director
  • LA at the moment.

Posted 16 July 2010 - 12:10 AM

Just did the 12v RV light bulb trick tonight. It worked perfectly, for lack of an even better word. Put that one in the back of your mind somewhere.
  • 0


FJS International, LLC

Metropolis Post

Willys Widgets

Aerial Filmworks

Gamma Ray Digital Inc

rebotnix Technologies

Media Blackout - Custom Cables and AKS

Opal

CineLab

Glidecam

Ritter Battery

Technodolly

Paralinx LLC

Rig Wheels Passport

Visual Products

Abel Cine

Wooden Camera

CineTape

The Slider

Broadcast Solutions Inc

Tai Audio

Technodolly

FJS International, LLC

Glidecam

Metropolis Post

The Slider

Rig Wheels Passport

CineTape

Aerial Filmworks

Gamma Ray Digital Inc

CineLab

Visual Products

Wooden Camera

rebotnix Technologies

Broadcast Solutions Inc

Media Blackout - Custom Cables and AKS

Abel Cine

Paralinx LLC

Tai Audio

Opal

Ritter Battery

Willys Widgets