Shooting explosions at night

[Arthur Levy]

Can anyone give me their thoughts on shooting explosions at night? I would like to avoid the rolling shutter problems. I plan to shoot some footage a 4K and some a 2K at 120 fps with a HD zoom on a B4 mount. Any experience or tips with shutter speed and exposure would be greatly appreciated.

 

[Brook Willard]

I wouldn't be as concerned about the rolling shutter artifacts [which are very minor as of build 15] as much as exposure. The first time I had to shoot an explosion digitally, I had the pyro guys set up a small mortar with a little gas inside. They fired it, I found the stop during the explosion that looked the best [read: not too much clipping to maintain the color] and then lit the environment to look appropriate at that stop. I wouldn't need to do it again [with that particular camera, it wasn't a RED], but it was a great 5-minute exercise to make sure we got it right the first time. When I shoot an explosion on a RED, I'll do the same exercise the first time around to make sure I get it right.

I'm reminded of the explosion in the Soderbergh footage. I don't want to comment on whether or not it was planned, but I found it about 1-2 stops hot for my taste. It resulted in a little too much clipping - enough to make the explosion look like a glowing white ball with orange fringes. I think it's enough that an audience would notice something different about that explosion versus a "normal" film explosion.

Since the RED doesn't really have a shoulder to speak of, you'll want to be more careful with exposure than you would be with curved digital cameras.

I'll leave the shutter speed discussion to others.

 

[Christoffer Glans]

I have no Red One experience but what I do know about shutters is that you shouldn't keep it the same as in normal speed. I think you should double it if you shoot 48fps.

Most slow motion footage I've seen shot with red is looking awful in my taste.
The image is fine, but the shutterspeed looks like a family videocamera.
You need more crisp images with higher frames per second. So, if you shoot 24fps at 1/48 shutterspeed, then to get an equal look at 48fps you need 1/96 in shutter speed.

I believe my calculation is right. Anyway, you should increase your shutter speed at higher fps or else you'll get unnatural motion blur compared to normal speed.

 

[Steve Sherrick]

Brook, glad to know I wasn't the only one who thought that explosion looked weird in the Soderberg footage.

 

[Finner]

If you can work it in the schedule and if the location works shoot the explosion at dusk and shoot it dusk for night. If you have shot day for night before then you will find dusk for night to be quite easy. This will help with the large exposure ratio between the shadows and the explosion. If you rate the camera at 8-8.5 stops of dynamic range you will be fine, any more then that and you will clip whites and end up with really noisy shadows.

 

[Michael Brennan]

Petrol or oil flames can be easily seen in daylight, they are quite bright!
Gas flames less so.

So you'll need to choose a healty stop and light the surrounding area or you'll get very little flame detail at the height of the explosion.

A multicamera setup where exposure is bracketed between cameras is an idea.
Shooting at dusk even better.




Mike Brennan

 

[Stuart4660]

I have no Red One experience but what I do know about shutters is that you shouldn't keep it the same as in normal speed. I think you should double it if you shoot 48fps.

Most slow motion footage I've seen shot with red is looking awful in my taste.
The image is fine, but the shutterspeed looks like a family videocamera.
You need more crisp images with higher frames per second. So, if you shoot 24fps at 1/48 shutterspeed, then to get an equal look at 48fps you need 1/96 in shutter speed.

I believe my calculation is right. Anyway, you should increase your shutter speed at higher fps or else you'll get unnatural motion blur compared to normal speed.

I've shot a fair few pyro fx on film and what you say is correct but the other way around - if you close down the shutter angle at high fps you end up with a strobe effect i.e. small parts of action are caught at even higher speed. This makes fire (or an exlposion) stutter and break up into individual hard flames - motion is lost. Think of it like shooting with a strobe light - same sort of thing. Opening up the shutter (or staying 180) helps keep put back some of the motion blur.
Watch out for the pyro guys saying 'Ok lets give it some' and suddenly your test exposure jumps 6 stops! It's happened to me a few times - they love their big bangs.
Stuart G.