Shooting with projections

[Luke Kokinos]

Hey all,

I'm directing a film late next year that involves a handful of effect shots, and to match the style and time-period of the film, I want to use a projection system in place of green screen. The idea is the use miniatures to shoot, say, a train rolling off track, adding digital effects such as sparks, debris, and smoke. Then taking that, projecting it on a 12-15' (approx) screen and having actors in a shot framed so the projected image is the background.

I am aware of the detailed shots that will have to be omitted to keep suspension of disbelief. I plan to use this effect seldom, and it is meant as visual homage to older films.

So what are the drawbacks and limitations? Any thoughts on how this could go horribly wrong?

Thanks in advance!

 

[Chris McKechnie]

I'd hire a company who specializes in projection and mapping. Just renting a projector and going by it willy-nilly won't produce good results (most of the time).

As you know, you'll also have to nail the lighting to match the composite projection.

 

[Björn Benckert]

Things to have in mind. Depth of field and focus point.
When you shoot the miniature you need massive amount of light and close down heavily and also set your focus point where the foreground actors should be. As there is a difference in relative sensor size / distance to camera in the two setups you need to do the above to compensate. There are mathematical charts showing how much you should close down and so on but I would actually not read to much into it and instead do scaling tests with the given camera and lens to visually find the same DOF.

The focus distance should be scaled to the set. So if you in the setup with a miniature of built 1:100 and then in the big set 5 meters to the actors / focus point and camera on 1 meters height.

The above would mean that in the miniature your center of lens would land on 1cm above ground... and you need to set focus on 5 cm.... Which most definitly means that you need a snorkel lens like the revolution lens system or similar that has extreme close focus and small enough lenses to get really really close to the ground. I think their diameter is about 3 cm so as you see my example above would not really fly, you would need a larger scale miniature or elevate the lens for the actors to at least 2 meters....

So yes, plan it well do tests both as 3D animatics (before building sketch sets) and then real test with real camera and projector and then shoot the plates.. Even if you don't want it to look perfect I can assure you that the guys that where dealing with these kind of setups back in the days actually where really good at what they where doing and still most of it looks like crap with todays measures so if doing a tribute to all of that I know it takes quite an effort to make it look like one.

Then also if you got sparks and bright elements and such in the projection you need a pretty strong projector to be in level with your fore ground light setting.

There can also be issues with the redraw of the projector so make sure that you get projectors that play well with the given camera, usually it's possible to make it work with shutter speed and or sync boxes. Last time I was fiddling with projectors we shot on film... and yes the first day was crap due to no sync between projector and camera even though we had it on the tech day.

So quite a fun thing to do but it comes with quite a bit of struggle far more than I could imagine so I have not done it again since then...

 

[Luke Kokinos]

Thank you both very much. It has made me reconsider the number of shots like this. And regardless, I will have a back up story board sequence to assure that I have something to fall back on, if the projections turn into a total nightmare.

Out of curiosity, and I know this may make me sound dumb, but how much leeway would be obtained by using more shallow focus, either in the miniature shots, or the shots against the screen? Certainly not trying to trivialize any of this by suggesting focus would fix it, but just curious if it would make a difference.

Thanks,