I'm working on a short that involves people watching fireworks - we don't actually ever see the fireworks

There is a scene with a young girl 8yo watching and I was going to put a large monitor on a stand in front of her so she has something to watch and it's easy to sync up sound in post from the actual fireworks footage. It's a close up so we just see the colours on her face

The main scene ends with a a wide shot that tracks in on a mother & daughter watching the fireworks. Coloured lights going off randomly have been suggested but that's a lot of work in post getting the sound to match and wouldn't look right IMO. I'm thinking of a projector set up high showing the fireworks colours in sync with the actual fireworks

I did a quick test with a small projector but realised you cant show the actual fireworks on the face, I need to replace the actual fireworks with block colours with the same intensity and timing.

I'm not sure if this will work or if it's viable - anyone done anything similar?

Since no-one else responded and if you haven't worked it out for yourself - bright fireworks wash the whole scene with the predominant color of the firework. Do it in post. Try adding a color overlay same color as the predominant firework and keyframe the alpha, from 100% (fully transparent) where there's no firework to say around 30% (whatever works for you) when the firework is brightest. I wouldn't worry too much about the sync, fireworks never sound in sync anyway due to the distance the sound has to travel.

Do it in post - seriously?
I've attached some stills of fireworks on faces, admittedly the fireworks are pretty close and bright but but I can't see a way of realistically achieving that in post.

Hi Paul,
did you try my suggestion? I had to do something similar for disco lights, should work just as well for fireworks. Just add a color overlay and keyframe the color and the alpha (i.e transparency) of the overlay. I've posted a three second sample using one of your stills on Vimeo, shows the effect (also some crude masking to show some fireworks which you can ignore, just play around with the settings until you get the look you want): fireworksglow on Vimeo.
cheers, Rainer

ahh - I see what you mean but I don'w want to actually show the fireworks, just the light on their faces and surrounds

Hi Paul, I may have misled you by adding the fireworks - they're completely irrelevant to changing the color wash on the scene. An overlay isn't the only way - I thought you'd probably tried the obvious - keyframing color balance adjustments - and were looking for something maybe more natural. If you're doing color balance, also play with the gamma to adjust brightness and mask the sky so it stays black. You didn't say what NLE you're using, but I think most can handle this. Oh dang, here's another example on Vimeo at Fireworks Glow 2 on Vimeo using CB, its random, but you get the idea. Maybe PM me if you don't think it's what you want or you're still confused.

I agree that changing the color in post is the cost effective way to achieve the result. As long as the audience believes the effect, it doesn't matter how realistic it is. In fact, realism can often be the wrong approach. Deliver what the audience expects to happen, not what really happens. (A good example is audio in a tile bathroom. The real audio usually sounds terrible and distracts the viewer. Dry audio with a moderate dose of nice sounding reverb gives the viewer what they expect.)

For a physical solution, I imagine multiple lights with color wheels (gels) and irises or shutters. Turn the wheel to red. Open the shutter quickly and close slowly. Another grip turns their light to green and operates the shutter. A third person overlaps with blue. Maybe, rather than a shutter, you use a mirror wheel (like they use for simulating lights going by a moving car), but this might create an unwanted sweeping effect, unless you can turn the mirror in and out of position quickly. Shutters would be more accurate but would be more difficult to build. And with gels and a wide view, you'd need huge lights on tall stands, each with operators. (Maybe they control the shutters with ropes.) This isn't a low budget approach.

The advantage would be real shadows and blended hues.

Regarding sound, it's correct that the sound actually comes quite a bit later than the light. However, for film it's not a bad idea to minimize the delay. Experiencing this with live fireworks, I always *think* about the delay because it remains a strange, counter-intuitive sensation. With a small or negligible delay in film, people will accept the experience - except the science geeks who will think about it, but they'll think about the delay even if it's technically correct. :)

Yeah, I'd do it in post with a very small delay from light to sound.

thanks Rainer & John - it makes sense now - I think that will give me the result I want.