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instant-on light?


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#1 Jance Allen

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Posted 23 April 2009 - 12:35 AM

Is there a type of light that gets to full brightness instantaneously (or nearly so)? Not a flash, but a light that when switched on won't take multiple frames to light up at 72fps.

Thanks for any help!
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#2 Ryan Thomas

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Posted 23 April 2009 - 03:08 AM

I believe there is a company called Lightning Strikes! that manufactures a bunch of different lamps that will flash instantaneously. I don't know if it can flash on though...That should get you somewhere...

Edited by Ryan Thomas, 23 April 2009 - 03:08 AM.

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#3 robert duke

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Posted 23 April 2009 - 09:45 AM

LED's seem pretty quick, I havent used them in that fashion but you might try.
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#4 Jance Allen

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Posted 23 April 2009 - 12:11 PM

Thanks! Looks like Lightning Strikes became www.luminyscorp.com. I'll contact them and see what their options are.

A couple of people I've asked have also wondered if LEDs light up fast enough. Might have to just try.
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#5 Karel Bata

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Posted 23 April 2009 - 05:08 PM

An old stage lighting trick: find a way of pre-heating the lamp (maybe on a dimmer) so it is already partially on. It will come up to full a lot quicker.

Or edit out the frames in which the lamp is fading up?

You didn't say what the lights were being used for. Fluorescents can be wired so the 'heater' is permanently on and they come up immediately. To be honest I haven't a clue what that means, but I overheard it once. Might be worth looking up... ;)
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#6 Brett Blackwell

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Posted 23 April 2009 - 05:13 PM

you could also look in to http://www.meggaflash.com/

Thanks! Looks like Lightning Strikes became www.luminyscorp.com. I'll contact them and see what their options are.

A couple of people I've asked have also wondered if LEDs light up fast enough. Might have to just try.


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#7 Michael Collier

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Posted 23 April 2009 - 06:30 PM

LEDs come up to full brightness in about 5ms. so at least enough for 200fps.
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#8 John Brawley

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Posted 23 April 2009 - 08:55 PM

Is there a type of light that gets to full brightness instantaneously (or nearly so)? Not a flash, but a light that when switched on won't take multiple frames to light up at 72fps.

Thanks for any help!



LED's can certainly do that. But will they be bright enough for what you want to do ? What are you trying to do ???
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#9 Jance Allen

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Posted 24 April 2009 - 12:20 AM

We're shooting motion control at 72fps, and we basically need the light to be fully on within one frame. The camera is moving so we can't edit out the ramp-up frames. But the basic gist of the effect requires the light(s) to be fully off up to a certain timing point, and then instantly fully on at the next frame, with no lighting ramp-up time.

Sounds like we need to see if we can find some LED panels. We're in Seattle so I'm not sure what's available.

And it's of course last-minute, as we're shooting on Sunday.

We're not screwed without it, and this is just a test shoot, but it would be cool to test this effect while we're at it.

Thanks for all the replies!
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#10 John Brawley

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Posted 24 April 2009 - 12:28 AM

We're shooting motion control at 72fps, and we basically need the light to be fully on within one frame. The camera is moving so we can't edit out the ramp-up frames. But the basic gist of the effect requires the light(s) to be fully off up to a certain timing point, and then instantly fully on at the next frame, with no lighting ramp-up time.

Sounds like we need to see if we can find some LED panels. We're in Seattle so I'm not sure what's available.

And it's of course last-minute, as we're shooting on Sunday.

We're not screwed without it, and this is just a test shoot, but it would be cool to test this effect while we're at it.

Thanks for all the replies!



Several years ago I conceived and designed (with the help of others) an LED based lighting system that did just this. (as one of many features)

It took the shutter pulse from a camera or video sync and you could have the light on or off, in or out of phase. You could also have individual colour channels fire at different points and different numbers of times within the shutter cycle. I built several working prototypes, but i had issues with the LED's being of a good enough CRI. I was mixing RGB LEDs and they are so monochromatic you end up with big gaps in the spectrum emitted. You also end up with difficult to solve shadow problems from hundreds of small point sources of light with different colour shadows ! Diffusing them or collecting them to reduce this usually meant loss of light output.

Im sure they aren't insurmountable problems.

You could easily custom build some electronics to read your camera's sync pulse and then build a one off light to do it. As far as I know there's nothing that can do this commercially yet.

jb
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#11 Jance Allen

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Posted 24 April 2009 - 01:30 AM

Very interesting. If this test is successful I'm sure I'll be following up on your idea. Thanks!
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#12 John Brawley

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Posted 24 April 2009 - 01:33 AM

Very interesting. If this test is successful I'm sure I'll be following up on your idea. Thanks!



I notice you have a post background.

One other use would be for motion tracking in slow shutter speed shots or objects that move quickly within a frame. One idea i had was to hit small scotch-light trackers at known intervals within a slow shutter frame. Make it a lot easier to do any motion tracking when there's lots of motion blur. I in fact built a one-off rig for exactly this for a job a couple of years ago.

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#13 Phil Rhodes

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Posted 24 April 2009 - 02:00 AM

Beware white LEDs. The blue LED emitter comes on with classic LED speed - and it's a lot less than 5ms; Sony's Laser Link technology, which uses an infra-red LED (not a laser) gets SD video down LED bandwidth. However, the yellow emitting phosphor on the front of the chip may take a while to get up to full output, so you'll have something that flicks on more or less instantly as a blue light, then fills in with yellow to white over the next few microsomethings.

Depends how fast you want it.

If it's motion control of a static object, you could just shoot two passes.

P
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#14 Karel Bata

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Posted 24 April 2009 - 08:26 AM

Motion control? Might not be relevant, but one pass with the light off, and another with it on, then do it in the edit?

EDIT: Aw damn! the previous post just said the same thing...

Edited by Karel Bata, 24 April 2009 - 08:28 AM.

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#15 Chris Millar

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Posted 24 April 2009 - 09:13 AM

Several years ago I conceived and designed (with the help of others) an LED based lighting system that did just this. (as one of many features)


Did the same with strobes - to shoot 72fps youd have to have a chase of them as they cant charge that fast, again using diffusion to sort the shadows - also we were stuck with the very very low 'shutter angle' of the strobe pulses, LED's wouldn't have this issue ...

I'm interested, does anyone have an idea of how to hijack any of the myriad signals that video/digital cine cameras output so that something similar could be done with them ?
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#16 Karel Bata

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Posted 25 April 2009 - 06:00 AM

Unilux lights, as used with photosonics cameras, should meet this spec. Just hire them in with a technician. http://www.unilux.co...ustry.php?iid=5 But they cost!

As mentioned above, a problem (or asset) with ultra short duration lighting is that the results can look a little too crisp - you'll have no motion blur:
Posted Image

Edited by Karel Bata, 25 April 2009 - 06:04 AM.

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