Miniature fire effect

Andy Boreham · December 28, 2006

Hey all!

Will be shooting a miniature house in 1/12th scale that will be set on fire for a short film.

I've heard of the equation used to work out frame rates but was wondering if it's all that important, well mainly since my camera only shoots as slow as 48fps and not the 84 that I should be using as per the equation.

So basically I wanted to know if anyone has experience with miniatures, namely fire, and if 48fps will be fine?

Also any other tips and trick would be greatly received! I'd also love to see photos of anyone's miniature work.

Thanks heaps guys :)

Edited December 28, 2006 by Andy Boreham

Zamir Merali · December 29, 2006

If your camera only goes up to 48 fps then thats the only choice you have. I would shoot it at 48 and then see how it looks after telicine. You can always use a computer program to slow it down more. Combustion, aftereffects and alot of other post programs can do it. I've heard of another one called twixtor that seems to give the people on this site good results:

http://www.detonationfilms.com/UnitK-3.html

Jaan Shenberger · December 29, 2006

the correct framerate for 1/12 would be 83 fps. i'd give you the formula, but i dunno how to type the square root symbol. it's easy to find online, as well as plenty of other info regarding shooting miniatures. try checking CML.

one thing to note-- fire and water do not scale well, meaning that you need to get your scale ratio as low as possible if you're aiming for realism. often 1/2, 1/3, 1/4 are used for miniatures involving fire or water... though a professional pyro person can really help in achieving scale in explosions and flames (via different accelerants).

and if you have a framerate ceiling (ie. 48 when you really need more) and are planning on using twixtor, etc, then be certain to adjust your shutter to correlate to the shutter speed/angle of the "final" framerate. otherwise, you may end up with an unnaturally high amount of motion blur.

best of luck.

James Steven Beverly · December 29, 2006

The problem with most minatures looking fake for a fire effect is that the models are too small. Fire doesn't "scale" down well, so models have to be big. The rule in most general terms is 1/8th scale minimum, but with a house, 1/12th may be fine. I think the other critical choice will be the lenses you use. Although I haven't tried this, I would bet using a longer lens and setting to camera back a ways will help flatten the image out and give you a more realistic look to the model. Also if you're not aware of this, you paint contact cement onto the areas you want to burn and will have much greater control over how the flames spread over the minature. I would also add smoke to help sell the illusion. A smaller fire won't produce the amount of smoke an actual structure fire would plus the smoke will help to obscure the flames and hide any discrepencies in scale. Again, I've never tried this but you could do some tests with some quickly fabricated "stand in" walls and see how the scale works at least that's what I would do before attempting it on a detailed scale model. Just a thought B)

Edited December 29, 2006 by James Steven Beverly

Will Earl · December 30, 2006

Fire and miniatures. Long time since I've seen the two used together.

From memory the calculation is...

sqrt(scale) * normalFPS

And I agree with James on the smoke, if you can get some thick, dark smoke pouring out of the house then it would possibly sell the effect by itself.

Andy Boreham · December 30, 2006

Thanks for all of the tips, guys - really appreciate it.

The reason I'm using 1/12th scale is because parts already made (windows, doors, etc) are readily available, ie: dollhouse scale. So really I think it's a great 'practice' size, if nothing more.

The effect I'm looking for isn't the whole house engulfed in flames, instead I'm looking for the start of a fire ie: contained to just one room, with mostly black smoke and small 'licks' of flame out of the window frame. I think this will be more easily achievable in that scale???

You guys mentioned 'Twixtor' a lot, so I did some searches online and found out a little bit but not much. Is it a program in itself, or just a plugin? If the latter, can I use it in After Effects 6.5?

Also, I'm wanting to get this blown-up to 35mm to see how Super 16 - 35 looks (am doing a job where I can hitch this test on the end and not have to pay for the transfer - *evil grin*). Would Twixtor mean I don't have a smooth transfer to 35?

I also have one more question. Would you guys suggest shooting this outdoors with natural light (I want to do this in the day time) or should I do this with simulated daylight?

Thanks everyone, and have a great New Year! :)

Andy Boreham · December 30, 2006

...one more thing. How do I create black smoke?

Will Earl · January 1, 2007

Regarding retiming software, typically they're used as plugins for compositing programs like AFX, Shake, Commotion, etc. Aside from Twixtor, there is Retimer (Realvis, also sells a standalone program) and Kronos (The Foundary, inplemented into AFX 7). These programs do the same thing, just how they do it differs slightly - I'm sure there is someone out there on the Interweb who has done a comparison.

There is a point at which a retimed shot will fall apart and you'll start to see weird distortion artifacts. Shooting at 48fps you should have enough information in the shot to retime to 83fps.

If this horrid Wellington weather gives you a nice day then aim to shoot this outdoors, save you having to recreate sunlight.

Cheers,

Will

James Steven Beverly · January 2, 2007

...one more thing. How do I create black smoke?

What I would use is smoke bombs. They're relitively safe and 3 or 4 inside your model should produce a ton of smoke but again I would test the effect first. You can try using charcoal brickets. Burning oil will also produce thick black smoke but that's stictly an outdoor effect and it leaves a residue and you need to be careful with it.

Andy Boreham · January 5, 2007

Awesome thanks again guys. Am looking into that retiming software and have found a recipe online for home-made smoke bombs...

Will post some footage in about a month when I'm done!

:)

Bob Hayes · January 8, 2007

I think I?d be inclined to do it mainly with smoke and light. Put a bunch of orange lights on dimmers inside the house get some smoke rolling and back light the smoke with the lights. The glowing smoke may look much more realistic. Place your real fire sources in a few very limited locations.

Joe Giambrone · July 26, 2008

It just occured to me that green screens placed inside the windows could be replaced with images of larger flames. That way you don't have to scale the flames so much, which is where the limits come in.

Jim Keller · July 28, 2008

To help the smoke scale better, you may want to try some tests using compressed air to "churn" the smoke (said with the caveat that I've never tried it).