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Exposing for Fire


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#1 Nick Centera

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Posted 09 January 2011 - 01:44 AM

Hey, so I was wondering how you would go about exposing for fire? Not really campfires or anything constant like that, but more like explosions or quick bursts where you can not just light it up to get a meter reading? I am assuming the answer would be tests, but if any other words please let me know. Thank you

Nick
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#2 David Mullen ASC

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Posted 09 January 2011 - 02:18 AM

Hey, so I was wondering how you would go about exposing for fire? Not really campfires or anything constant like that, but more like explosions or quick bursts where you can not just light it up to get a meter reading? I am assuming the answer would be tests, but if any other words please let me know. Thank you

Nick



There's no right or wrong exposure, it's just that the more you stop down (or the slower the film stock) the darker the fire will be. Look at "Gone with the Wind", you're talking about an effective 10 ASA at best for the big fire scenes like the Burning of Atlanta, probably shot at f/2.8, so you'd get the same exposure at 320 ASA if you shot at f/16! In that movie, the fire exposed as a deep orange-red.

Most of the time, you are trying to light the space surrounding the explosion, it isn't a pitch-black frame until the moment of the explosion, so the real question is how much can you light the scene so you can stop down to hold more detail in the explosion?

I mean, a bright fire has a nice look on 200 ASA film at f/5.6, but who can light a night exterior to that level? What normally happens is that you light to as high a level as you can and then shoot the explosion.
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#3 Nick Centera

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Posted 09 January 2011 - 02:25 AM

What normally happens is that you light to as high a level as you can and then shoot the explosion.


So could you say that depending on your distance to the explosion, the fire could be over or under exposed? Like, the further away the less chance to overexpose (but obviously harder to light evenly if its a night scene) and vice versa.
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#4 David Mullen ASC

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Posted 09 January 2011 - 12:13 PM

So could you say that depending on your distance to the explosion, the fire could be over or under exposed? Like, the further away the less chance to overexpose (but obviously harder to light evenly if its a night scene) and vice versa.


Distance doesn't affect the exposure. It's pretty hard to underexpose an explosion at night, especially if you are working with 500 ASA film. The real problem is the post-explosion fire rather than the flash, because eventually it will die down. But usually the movie cuts away to something soon after the explosion.

The only way that distance makes a difference if the size of the fireball is small in frame, then exposing for the surrounding space is more important, whereas if the explosion fills the frame, then the exposure should favor that. But the explosion itself doesn't get dimmer as you back away from it. The explosion is like a practical lamp in a room -- the farther away you get, the more you are going to expose for what the lamp is lighting rather than the lamp itself.
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#5 John Sprung

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Posted 10 January 2011 - 06:10 PM

The thing that saves you on explosions and fire is that it's not like a human face or an ordinary room where the audience knows pretty much what it should look like. More or less exposure makes it look like a bigger or smaller explosion, but it never looks wrong.




-- J.S.
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