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Author Topic: Anyone know how this is done?  (Read 1315 times)

Stephen_Ramsey

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Anyone know how this is done?
« on: May 07, 2018, 01:01:48 pm »

Was watching SNL, and thought these lights/effects were really cool (both the lights surrounding the rapper, and the backline light effects).

https://youtu.be/l2P2qbr-_Ps?t=2m46s
(effects start around 2:45, video should start there)

Can someone explain to me how this was done or what light/equipment was used? Thanks in advance!
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Jeff Lelko

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Re: Anyone know how this is done?
« Reply #1 on: May 07, 2018, 03:35:29 pm »

Can someone explain to me how this was done or what light/equipment was used?

Yes, but first you must change your user name to your actual first and last name per the forum rules you agreed to when registering.  No one is able to help you until you follow the rules.
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John Fruits

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Re: Anyone know how this is done?
« Reply #2 on: May 08, 2018, 04:49:34 am »

I was wondering the same thing, I found this explanation at another forum (Controlbooth).
It isn't something you can see live, but has to do with the lasers and tv frame rate.
Donald Glover
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Stephen_Ramsey

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Re: Anyone know how this is done?
« Reply #3 on: May 08, 2018, 10:44:21 am »

I was wondering the same thing, I found this explanation at another forum (Controlbooth).
It isn't something you can see live, but has to do with the lasers and tv frame rate.
Donald Glover

Thank you very much for the link! Very fascinating...not being a lighting expert, I was absolutely mind blown...glad to see I wasn't the only one, and that the logical side of my brain wasn't betraying me by not thinking that was possible IRL without some sort of hologram stuff that I don't understand!! Thanks again!
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Dave Garoutte

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Re: Anyone know how this is done?
« Reply #4 on: May 08, 2018, 01:07:39 pm »

I can see this is like one of those digital waterfall type fountains, but...
I don't get how the pulse of laser, travelling at the speed of light (982,080,000 feet per second), could be short enough for a camera frame to capture it as a segment.  It would have to be 1 billionth of a second long.
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TJ (Tom) Cornish

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Re: Anyone know how this is done?
« Reply #5 on: May 08, 2018, 03:33:09 pm »

I can see this is like one of those digital waterfall type fountains, but...
I don't get how the pulse of laser, travelling at the speed of light (982,080,000 feet per second), could be short enough for a camera frame to capture it as a segment.  It would have to be 1 billionth of a second long.
It's not that the speed of light is fast, but rather the camera sensor is slow that makes this work.  In the good old analog days, the electron gun scanned the image from left to right starting at the top and working down.  Digital cameras don't work quite the same way, but the effect is the same - not all of the image is captured at exactly the same instance - the camera sees the laser in one place when it starts capturing the frame, then by the time the camera is capturing another part of the image, the laser has moved, so there's a "hole" in the laser beam.

This is often called "rolling shutter", and there are some interesting videos that demonstrate this phenomenon.
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Dave Garoutte

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Re: Anyone know how this is done?
« Reply #6 on: May 08, 2018, 04:00:38 pm »

Ah, the difference between CMOS and CCD chips.
The CCD captures the whole frame at once and the CMOS does the raster scan like a CRT.
That's also why GoPros make propellers look so weird.
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Jeff Lelko

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Re: Anyone know how this is done?
« Reply #7 on: May 08, 2018, 06:02:41 pm »

That's also why GoPros make propellers look so weird.

Yep, and in this case exploiting the effect instead of trying to remove it.  If there was ever a doubt as to the trick is done the artifacts visible starting around 3:25 give it away. 

To OP about which equipment was used, they're (obviously) lasers, and I'd wager they're KVANT units - hard to tell from which exact series though. 
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James Feenstra

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Re: Anyone know how this is done?
« Reply #8 on: May 08, 2018, 11:50:00 pm »

Assuming this is childish gambino on SNL (the video isn't available in Canada), I know the laser guy who did the show

it's entirely done with camera frame rate tricks and playing around with scan rates/etc
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Len Zenith Jr

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Re: Anyone know how this is done?
« Reply #9 on: May 09, 2018, 12:00:50 am »

Assuming this is childish gambino on SNL (the video isn't available in Canada),

For Canadian viewers: https://www.youtube.com/watch?v=m1xkLqd1wdU
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