Electrical arching effect / Rolling shutter

[Danny Gagatt]

Hi,

I've got rolling shutter concerns for a multicam shoot I've been called to supervise which is making use of Teslar coils to create an on going electrical arching effect in the background of the shot, with artists in the foreground.

The set is to be lit quite dark, but with the foreground being more pronounced than background action. I'd expect an overall exposure set for around T2 / T2.8.

The client has also spoken of their desire to potentially shoot anything up to 100fps, so with previous experience of rolling shutter issues with strobe lighting (Macs - which was fixed by re-timing) and Cooke S4's @ 100fps, I'm just wondering what could be expected, or if anybody out there has shot something similar. Lightening bolts anyone?

I'm aware that S4's have their own flaring characteristics, so the choice of glass isn't set in stone at the moment. Ideally, I'd like to get the DP to shoot some tests, but it's early days yet.

Thanks in advance.

 

[Dominic Jones]

Hmmm... Good question!

The thing about Tesla coils is that they do not produce (in normal usage, at least) flashes and bolts of electricity, but rather a constant - if moving - arc.

I would guess - and I must stress it is a guess - that you won't run into the "split-frame" issue or anything similar with tesla coil arcs. You might well get some distortion in the image as the arc moves - especially if it moves quickly - but I doubt that will be overtly present to the naked eye. Should be even less of an issue at higher framerates, I would have thought, but maybe I've missed something...

Hope that helps, and would love to know what you find out - please report back!

Cheers,
Dom.

 

[Jeff Kilgroe]

Tesla output is constant, but if there are multiple electrical arcs, sparks or tendrils coming from the coil, they have a tendency to dance or instantly snap on and off or arc to different locations. So split-frame exposures can be of concern. Likewise, split-frame exposure would be a concern on this shoot too if you guys were shooting with a mechanical shutter camera / film camera.

Best thing to do is shoot some tests to identify all the potential issues and work from there.

Here's a tesla coil in action inside some idiot's house...

 

[Irri]

Here's a tesla coil in action inside some idiot's house...

Ha ha ha. That made my day.