6 replies to this topic

[Vincent Aalbertsberg]

Hello, just a quick question here : I'll be soon shooting a video, and there will be some photography flashes in a scene. So I wanted to know if there was a way to avoid the ugly effect that flashes make on video, maybe by tweaking the shutter speed or something, or if real flashes are just not usable (i'll be using a DSLR so, you know, rolling shutter).

 

Thanks !

[David Mullen ASC]

Not much you can do about the flashes mounted to cameras going off in the shot, short of renting a camera with a global shutter. For off-camera flashes there are strobes with longer times that create less of a problem -- I read about an LED strobe that was used for "Straight Outta Compton" for example, shot on Red cameras with rolling shutters. I've used Lightning Strikes Papparazzi strobes without problems. Atomic strobes work OK too, though you have to find a cycle where it seems to sync with rolling shutters before it drifts again.

[John E Clark]

There is no real way to use a 'real' still camera flash and guarantee avoiding the partial frame issue.

 

On the other hand, in the Netflix series, "Jessica Jones", using a Red camera, one can see partial frames when there are flashes going of in the scene... so it would seem that some people are just ignoring this artifact of non-global shutter cameras. Sort of like ignoring the spokes of wheel changing apparent rotation direction depending on speed...

[Vincent Aalbertsberg]

Thanks for the very quick reply !

And I guess I will go Jessica Jones style, that's what I had planned anyways and I don't really have time nor money to rent new lights, but I thought it was worth giving it a shot ! Thanks anyway, your advices will most probably be very useful on futur projects.

Vincent.

[Satsuki Murashige]

I suppose the other thing you can do is to go through the footage later and either edit out all the half frames or replace them with single frames of white.

[John E Clark]

The 'bury it' approach does have some merit. Depending, one can see 'stylized' slo mo + flash which probably was done using some form of effect, rather than in camera, at least for recent versions. And probablly in the past, using manually controlled shutters on a bright light may have been used in the past.

 

Even for still photography, there needs to be a synchronization between the flash and the shutter, or 'slow' enough shutter(like in bulb mode, or 1 second shutter and manually actuated flash...) to avoid 'partial' frames. There were of course effects one could do in stills such as 'fast flash, slow shutter' to give a sharp+blur effect.

Edited by John E Clark, 08 December 2015 - 06:34 PM.

[John E Clark]

Oops... I should have been more specific... in 35mm Still photography, or for cameras that had a 'curtain' type 'shutter' mechanism, one could get partial frames depending on the shutter speed with a flash... because for higher shutter speeds the 'curtains' would just be open enough for a slice of the film to be exposed and that 'slice' would travel from one side of the film area to the other, or from 'top' of the frame to the bottom, depending on the implementation. I think 35mm mostly were side to side curtains...

 

The other type of shutter, the leaf shutter as part of the lens assembly, did not suffer from this sort of thing, as it was ether fully open, or closed, thus avoiding 'partial' frame results...

 

Since I don't have experience with Film film motion picture cameras, just on theoretical grounds it seems like they could also produce partially exposed frames depending on the speed of the flash, un-sync'dness with the shutter, etc. but perhaps less 'readable' than the block type artifact of the 'rolling shutter' digital read out pattern.