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How'd they do this flash effect without rolling shutter?

flash effect

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#1 Roger Alexander

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Posted 21 March 2016 - 04:23 PM

OK I'm back with another "how did they do this" question. I'm looking at the quick & bright light flash effects you can see at 00:10 and 00:16.

 

 

Most of the time when I try to do a flash effect with something like a strobe light, you get that "half the screen lit" effect because of the rolling shutter in the camera. Global shutter cameras I assume don't have this issue, but I only have access to rolling shutter cameras like the RED. So when using a RED, how can I mimic this strobe/flash where the entire scene is lit during the flash and not getting that rolling shutter problem? Previously I had tested with some cheap strobe lights and assume the light flash was just too quick for the shutter to grasp. But what if I used photography strobes? Something like the Alien Bee 800s for video? Would I still get the same problem? Maybe there's a more expensive strobe that allows you to change the duration of the flash for the camera to pick it up corectlly? Any model suggestions? How did they do this?


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#2 Phil Rhodes

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Posted 21 March 2016 - 04:53 PM

Actually, it does have rolling shutter artifacts in it. I suspect they cut around the worst of them. From about 33 seconds:

 

rolling2.jpg

 

This is one of the more obvious ones, but it's mainly visible in the way the flashes are often two frames long, and there's a certain vertical offset to the brightness between frames. Looking at the overexposure characteristic, I'd suspect this actually was Red.

 

There are reasonably low-cost rolling-shutter cameras, such as the Blackmagic Production Camera, which is probably the easiest way to solve the problem. Regrettably, the Ursa Mini 4.6K is to omit this feature, which I think is a very great shame.

 

Simply increasing the duration of the flash will not guarantee problem-free pictures. I wrote a whole article on it.

 

P


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#3 John E Clark

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Posted 22 March 2016 - 11:27 AM

Speaking of lightening... The Wife and I are going through the umpty ump hours of BTS clips that are on the "Hobbit" disks. In one clip there was a brief few shots of the light technician and how he controlled banks of Kinos to create the lightening effect seen during the 'Rock Men' fight scene.

 

The control board allowed the tech to fire off a number of the Kinos (they were wall to wall at the top of the set bay (perhaps 20-30 feet up)), and he had sort of a 'patch work' across the panels for a given 'lightening' flash.

 

They were using Reds (can't recall which model) to capture the 3-d, and I think they were using 48 fps. I don't know if there was any sync pulses coming from the cameras to allow the lights to be better synced with the frame capture.


Edited by John E Clark, 22 March 2016 - 11:27 AM.

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#4 Edward Lawrence Conley III

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Posted 22 March 2016 - 12:26 PM

You could try out a Dynalite M1000 and head.

 

Max power with 1 head you'll get 1/350 flash  but that may be too bright and unfortunately with flash- as you lower the output the flash speed increases 

 

Min Power on the flash unit results in 1/3000.

 

Probably need some ND for the flash heads.

 

PPR in Atlanta rents them.


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#5 Josh Tree Park

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Posted 24 March 2016 - 10:09 PM

I read somewhere that Fast and Furious 7's gun fight scene which was lit with bullet ricochet's was shot on film because they couldn't figure out a way to cut the ricochet's rolling shutter half frame flash... Just an FYI
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#6 Robin R Probyn

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Posted 25 March 2016 - 03:19 AM

But film camera is also rolling shutter ?


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#7 Brian Drysdale

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Posted 25 March 2016 - 03:45 AM

If the flash occurs whilst a film shutter is fully open, you won't get half frame flashs. You may get something as the shutter is opening or closing, which is a form of soft wiping effect,but this is a small percentage of the exposure time.


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#8 Phil Rhodes

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Posted 25 March 2016 - 05:14 AM

There's a lot of strobes used in Aliens where that effect is subtly visible - during long strobe bursts you can see the bright area move from bottom left to top right (as I recall). It's very, very subtle, and not nearly as objectionable as electronic shutter issues.

 

P


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#9 Robin R Probyn

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Posted 25 March 2016 - 07:17 AM

Yes all true.. but technically its a rolling shutter.. no..?


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