Any tips or tricks to get CMOS sensors to capture gun muzzle flashes?

[Adam Paul]

We were doing some tests yesterday for a movie we will be shooting where there will be some blank gun shooting involved. Surprisingly, 5 times out of 6 the camera would not capture the muzzle flash. Now we are going through the trouble of using blank pistols and machine guns instead of gas or electrical ones because we want the realistic muzzle flashes rather than do it in post which always looks kind of fake. But that's not any good if the camera can't capture it. Is there anything we can do to get the camera to capture it? We were filming 24p with a 1/48 shutter. The camera was the Sony EX3 which is a full raster 1080p camera but has a 1/2" CMOS.

 

Thanks.

[Adam Paul]

The CCD camera filming the making of captured it just fine, so it has to be something with the CMOS.

[Scott Fritzshall]

There shouldn't be any difference between sensor types when it comes to this. What it comes down to is that you're shooting 24 frames/sec, but that each frame only exposes for 1/48sec. Since the muzzle flash is very brief, you've basically got a 50% chance of catching any particular one during the time you expose. Your "making of" captured the others because it either had a different exposure time or simply because it was offset slightly in time from your EX3.

 

One possible solution could be to simply use no shutter: in other words have each frame expose for the entire 1/24sec duration. This will change the motion characteristics of these particular shots drastically, and rather unpleasantly in my opinion, but you will be guaranteed to capture every muzzle flash. I'd advise checking out cinematography.net; I'm pretty sure they've got an article on this subject.

[Adam Paul]

Thanks Scott.

I thought it was the CMOS because it's a known thing CMOS can't capture things like camera flashes and police lights because of the refreshing rates so I thought the same was applying here. I will give it a try with a 1/24th shutter.

How about slow motion at 60p? I can see the shutter setting being even a bigger problem here.

I will check cinematography.net as well.

[Adam Paul]

I just checked cinematography.net and found a topic called "24P & Shooting Fire" on the index list which I thought could be it but the link takes you to a shutter angle thread which has no mention of fire, muzzles or anything. It's just a question about shutter angle and T-stop compensation. A google search also turned u nothing on cinematography.net. Would you know where it could be? Thanks.

[John Sprung]

Slow burning blanks are what you need. Even on film, the fast ones will only show up half the time. The other half, they go off when the shutter is closed. Slow ones burn long enough to cover at least one frame, usually two.

 

A video camera with a 360 degree effective shutter should have very little problem with fast burning blanks. The only issue is if it has a rolling shutter, in which case the shutter edge passage could hit the area where the flash is, and get cut off. Look at some of the threads about strobes and the Red camera, there are examples that show the shutter edge being caught by a strobe.

 

 

 

-- J.S.

[Adam Paul]

Thanks. I never knew about slow burning blanks. Is that something you can buy at normal ammunition places like blanks or you can only find them in special effects houses and film places?

 

Also, there has been talkings of getting some cap firing machine guns. I'm thinking firing caps will also be characterized as fast burning?

Edited October 11, 2008 by Adam Paul