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Greenscreen through a window?


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Hi, I've searched the archives quite a bit, but really didn't found what I was looking for...

 

So we have a shoot coming up in about month, the location is bar interior. We are probably shooting with Panasonic AG-DVX100A. It's a day shoot, but the script calls for night. There's a big window (about 37' x 5') in the bar, and I wouldn't want to frame it completely out, so as I see it we have a couple of options. We could either just tent it black, which we must do anyhow, or we could composite a night street backround behind it later in post. It would look awful just tenting it black.

 

I have some worries about doing chroma keying, since I've never shot any blue/greenscreen stuff, but I have pretty good knowledge about exposing the screen and compositing later in post. The window has some basic bar-logos and texts glued to it and they are partially transparent. I'm wondering can they cause any problems with compositing? Also, if we want to keep the blinds on the window, can they cause any problems? Does the partial transparency look right when background will be composited behind the logos? We are doing the post work with Ultimatte.

 

About lighting it, I'm having some doubts because we can't get the chroma too far away from the window. Maximum is about 5', so I'm wondering how hard is it to get even light from up this close? We don't have access to unlimited fixtures, I was thinking of lighting the chroma with halogen floodlights. Do you think they give even enought spread? I could get probably about 20 of them and can also rig some of them up just out of the picture. Kinos are also out of the question, as we don't have the budget. We have access to some open-faces, fresnels and hmi's, but I though those halogen floodlights would be quite perfect for this. Just have to carefully measure their color temperatures and match other lighting to it.

 

I know consumer DV isn't the best format for composite-work, but I've understood it's doable. We have also the option of shooting chromas with dvcpro, but I think it's almost impossible to intercut with the dvx100a. Now we have a problem finding a big enough greenscreen for next to nothing...

 

I will be shooting some tests concerning these composites, which is rather nice.

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You don't have a lot of options so you're just going to have to do the best you can and try a couple differentg things on set. It'll be a good learning experience. There are a couple of things you'll have to be aware of though. You will need an evenly lit screen. Since you don't have a lot of lights or a lot of distance, try putting some bounce board on the outside of the bar opposite the screen and try bouncing light into it to light the screen. That way your bounce card becomes a bigger soft source which will give you broader and more even coverage. To avoid color bounceback on the window edges, try keeping the greenscreen 1 to 2 stops underexposed from your shooting stop. Ultimatte will probably be ok. I personally think Key Light in After Effects Pro is the best keyer I've seen, especially when using translucent forground objects like smoke and sheers.

 

But here's the most important thing. You'll need to have the camera locked off or you'll be forced into motion tracking your green screen element. If you don't it will look like crap. If that scares you, you should just tent it or put a flat or a brick wall or something outside the window.

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But here's the most important thing. You'll need to have the camera locked off or you'll be forced into motion tracking your green screen element. If you don't it will look like crap. If that scares you, you should just tent it or put a flat or a brick wall or something outside the window.

 

Thanks for the tips, although I somewhat knew most of them already. Well, it's nice to be reassured that I've though it through myself. I also have to check out that Key Light.

 

By the way, I was going for locked off shots, but was wondering about tracking. I'm under the assumption that duplicating the move on the greenscreen to a locked off plate video shot is impossible even though I'd have proper track marks on the screen? It's just not possible without motion tracking system, right?

 

I was just working as an electrician on a shoot where they composited computer generated graphics for moving shots. Then it's "simply" the case of duplicating the moves tracked from the tracking points, right? Maybe I should create some stupid looking, obvious cgi background in 3d ;) Well, just kidding.

 

Now I have to decide between tracking shots to that direction or showing a real background there, hmm.

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Then it's "simply" the case of duplicating the moves tracked from the tracking points, right?

 

Maybe that should be "$$$imply" duplicating the moves. ;)

 

To me, all this a big red flag. Sure, there are ways to do it, but I'm a firm believer that the solution to 90% of cinematography problems is to avoid the problem in the first place. Big window, small space, semitransparent signs -- each of these alone is a problem. Why intentionally take them all on if you can avoid them?

 

Try blacking the windows and do all your shots opposite the window during the day. Save the reverse angles for night, or even another location that can reasonably match.

 

OR, if you must do green screen try to limit those shots to tightly framed closeups, where you don't have to do the full 35x7 green screen -- just a reasonable 6'x6' or whatever.

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Maybe that should be "$$$imply" duplicating the moves.  ;)

:)

 

To me, all this a big red flag. Sure, there are ways to do it, but I'm a firm believer that the solution to 90% of cinematography problems is to avoid the problem in the first place. Big window, small space, semitransparent signs -- each of these alone is a problem. Why intentionally take them all on if you can avoid them?

 

That's true. But I think in this case by avoiding the problem *at all costs* I'm compromising too much. But I agree somewhat, the greenscreen is not going to work on this shoot.

 

Now I'm thinking of blacking the window out and maybe rigging some neon's inside the tent to emulate shop lights in darkness. And maybe lighting the street a little bit from high top angle, motivated by some streetlamps near by. I think it could look convincing enough, any thoughs? We could also get some extras to walk in the tented part of the street.

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