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Tristan Noelle

LED Lightning Effect

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Hello, I'm curious if anyone has used LED fresnels (Arri L7, Mole Studio LEDs, etc.) for a lightning effect. I'd like to be able to cue a lightning strike thru the unit's DMX control. I want to avoid tungsten because of the time it takes the filament to dim completely down between flashes. However, I'm not sure if there is a delay in the LEDs that would prevent an effective strobing or flashing effect.

 

I imagine I'll test it soon enough, but wondered if anyone had any experience or thoughts on the issue.

 

Thanks,

 

Tristan Noelle

 

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I think it would work. I used this weird LED light the aadyntech. It has a built in "flash" effect that you can trigger just hitting a button on the light.

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It may be worth investigating whether the lighting desk (or whatever you use to control it) supports limiting the range of DMX addresses output. DMX can control 512 devices and update each at 50Hz, but many devices support limiting the address range so that only a small number of addresses are output. This should increase the precision with which information can be sent - although there may be delays inherent to the device you're controlling that can't be mitigated with this technique.

 

P

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Hello, I'm curious if anyone has used LED fresnels (Arri L7, Mole Studio LEDs, etc.) for a lightning effect. I'd like to be able to cue a lightning strike thru the unit's DMX control. I want to avoid tungsten because of the time it takes the filament to dim completely down between flashes. However, I'm not sure if there is a delay in the LEDs that would prevent an effective strobing or flashing effect.

 

I imagine I'll test it soon enough, but wondered if anyone had any experience or thoughts on the issue.

 

Thanks,

 

Tristan Noelle

 

 

What sort of camera are you using. The issue here is that if the camera is digital, and does not have a 'global' shutter, the 'flash' duration may be such that rolling shutter artifacts are a result.

 

For an old fashioned method... tungsten lights behind venetian blinds would allow for the simulation of lightening, but mitigate such digital problems.

 

There is this thread currently running...

 

http://www.cinematography.com/index.php?showtopic=66183

Edited by John E Clark

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Thanks for taking the time to reply, guys. Pardon in advance if anything I say is mistaken as I'm still new to the whole DMX arena.

 

I'll be testing an A7s (rolling shutter...), alongside a Sony F5 or Dragon. Length of the flash is something I'm going to look at and see if it can mitigate the 'partial-flash' artifact.

 

I'm curious about the Arri L7-c as the unit doesn't have a built in flash or strobe function so whether the lightning is convincing will depend inherent delays in the unit; and whether the board setup I have can relay the programming quick enough. I want to use it because of the range of adjustments I can do without gelling; the film is a dream sequence and the director wants a variety of colors and options for lightning. I'll have some basic party/dj LED units with strobing functions I'll be playing with.

 

Thanks John, I checked out that post. I'm going to try and track down some DMX activated shutters; I know they exist but haven't ever dealt with them. They may be the best of both worlds. One of the reasons I want DMX is the ability to reliably sync flashes to cues in a rear projected video; its a VERY experimental project. QLab can do it using a midi signal to a control board with the proper setup. I'll be speaking to a projectionist about it.

 

Anyway, I'll update when do those tests. Thanks again.

 

Tristan Noelle

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Length of the flash is something I'm going to look at and see if it can mitigate the 'partial-flash' artifact.

Ultimately, you have to turn it on or off at some point, and if that point happens to be during the readout - which is hard to control - there's nothing you can do about it.

P

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Thanks, Phil. I fear you're correct.

 

It may just mean getting to a point where the director and I can live with it. The strikes are important at several parts in the script, but not ubiquitous. There may be a chance we can edit around the more garish artifacts provided we have options. We'll see.

 

The Epic/Dragon is on the table for the production camera (pending our producer's craftiness) and if available for testing, I'll push to add that TI PL Motion Mount; RED claims it will counter the effect. I'd consider a global shutter camera like BlackMagic, but need the light sensitivity. Thanks,

 

Tristan

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hey dude there is a brand of fairly bright led panel called the cream source which has a built in adjustable flicker setting which I can personally vouch looks pretty great as a small source lightening/flicker/strobe effect.

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It's been awhile since this post, but I did end up testing and shooting the short, so I figured I'd update. For the lightning effect I used Mole Baby Fresnel LEDs w/ 5pin DMX (5600k), daisy chained with one on each window. Using a cheap DJ DMX board we just flashed the units by hitting the blackout key rapidly.

 

The Mole LED's didn't have any latency issues when turned on and off with DMX; they were suitably responsive. I did try just flipping the on/off switch on the lamp's power cable, which was very delayed.

 

We ended up shooting with an FS7. The flashes were gelled pink, so they couldn't be too bright or they'd lose too much saturation (hence the Baby fresnels). They played as sidelight or back light, and because they went through windows they never really filled the frame with light, so the rolling shutter artifacts weren't an issue.

 

I'd use this system again for a lightning effect, but I'd want to test with the bigger Junior and Senior Mole Fresnel units for the intensity and see if they were as responsive. Being able to program different lamps at different intensities in the board and cue them when needed is pretty handy. I'll post some video when I get it. Hope this is informative.

 

Tristan

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Hello, I'm curious if anyone has used LED fresnels (Arri L7, Mole Studio LEDs, etc.) for a lightning effect. I'd like to be able to cue a lightning strike thru the unit's DMX control. I want to avoid tungsten because of the time it takes the filament to dim completely down between flashes. However, I'm not sure if there is a delay in the LEDs that would prevent an effective strobing or flashing effect.

 

I imagine I'll test it soon enough, but wondered if anyone had any experience or thoughts on the issue.

 

Thanks,

 

Tristan Noelle

 

 

 

Hi Tristan,

 

Could you explain "I want to avoid tungsten because of the time it takes the filament to dim completely down between flashes."?

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When you switch a tungsten lamp off, it takes the filament a short time (2-3 frames) to cool to the point where it is no longer emitting light. During that period, although the light is very dim, it's also very warm in color, which tends to ruin the lightning effect. In a recent movie, where I had to use a tungsten lamp for lightning effects, we had to color-time the flashes frame by frame to remove any hint of warm orange light.

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When you switch a tungsten lamp off, it takes the filament a short time (2-3 frames) to cool to the point where it is no longer emitting light. During that period, although the light is very dim, it's also very warm in color, which tends to ruin the lightning effect. In a recent movie, where I had to use a tungsten lamp for lightning effects, we had to color-time the flashes frame by frame to remove any hint of warm orange light.

 

Thank you Stuart.

Edited by Mathew Collins

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