Green screen question

[jfirma1]

I have a question concerning using a green screen.


I'm planning on shooting this short film soon and one of the scenes requires the use of a green screen. The idea of the shot is to have one of the characters look out a window and see a city scape with missile trails coming closer to the city. The window will be this:

The approximate size of the green screen will need to be 6 feet by 4in height and 4 feet by 1/4 inch width.

A few questions:

• Should I cover more than just the window with the green screen?

• Will it be better outside the window or inside?

It is pretty much impossible to cover the outside as it is on a second floor office. As you may be able to see, there is a tree in front of it as well.

• What type of material should I use for the green screen?

• There will be a person in front of the window at exactly that angle. Will this affect the green screen much and if so, any tips on how to get around this?

 

[Nathyn]

If the Greenscreen covers the whole window, just replace the whole window. Use the "Magic Glass" tutorial on Videocopilot after you've done your effect. Also, I've found 10 x 20 greenscreens on eBay for a very good price. You have to find them though.

-Nate

 

[msorrels]

It will look more realistic if you can put the green on the other side of the glass. But if you can't you could try using roll paper/large sheets (from an art/craft store) cut to fit the window exactly. Mount it to the window with clear double sided tape(clear so it doesn't shadow through the paper). Any bright green color should work ok. You'll have to fake the glass as well as what's behind it.

If you go with a large cloth green screen set up in front of the windows you might as well just pick a different room to film in. Lighting a large cloth greenscreen in front of those windows during the daytime is going to be a challenge. Replacing the whole wall is no walk in the park either. The paper on the window will be difficult to get lit right as well though. No short cuts there. Lighting the room with the outside daylight is always going to be the tricky part. You're going to have a hard time lighting it right, especially with light and shadows coming from the back side. Might be easier to film it at night.

If the camera moves you're going to need to do some tracking. Even if the camera doesn't move you may still find you need to do some tracking to stabilize the replacement. Might want to add some slightly different color green tape on top of the paper in L-shapes or crosses. I suspect the room will provide enough tracking detail, but it can never hurt to have more.

You technically only need to green screen the windows where people/objects move in front. The other windows could just be replaced(corner pinning) in whatever software your using(though having them all green may help cut down on the roto work, depending on what's in the foreground and how the camera moves). If you plan your shot right you may only need to green a small area of one window.

For something like this you need to get with whoever is doing the compositing and work out what will work best. There are always a few dozen ways you could do an effect, a couple of ways you personally could do it that would work, and maybe one or two ways that are actually best for you and your production.

 

[Nathyn]

In fact you can simply GS a wall versus the window. I mean it would be easier and you'd get to decide how big you want the window and how you want it to look. Lock down all the shots in front of said window and try to shot all the scenes that need to take place in front of that window in the same day or group of days. And I know we all love the idea of the green screen but you can also mask the window out.

-Nate