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Green Screen question

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Marc Lucas
Green Screen question
on Dec 5, 2012 at 5:00:25 pm

Shot a lady opening a window (from outside the window) the window was the main reason for the shoot. A green screen was placed behind the talent opening the window. The idea was to key in some kind of BG either a wallpaper texture or a room image. The problem I'm having is trying to create some space between the window and the BG image because if I was simulating a corridor or room is there any techniques that simulate the actual perceived 3D space? The window was shot at a slight angle not face on. Hope you understand what I mean


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Mark Suszko
Re: Green Screen question
on Dec 5, 2012 at 9:46:12 pm

Can you post a still, using the tools in this interface? This should be easy to composite in Apple Motion, assuming the green pulls a good key. I think what you're trying to describe for depth is the subliminal depth cue you get from controlled depth of field, where the background ( In this case the hallway) blurs by a specific amount. Am I getting warm?


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Mark Suszko
Re: Green Screen question
on Dec 6, 2012 at 7:27:25 am

That green screen is pretty tough. Too wrinkled and unevenly lit. Here's a quick and dirty "room" composited behind her using Motion. This is not nearly a final product, just a sort of place holder until you get the textures and things you want.

You import the greenscreen footage, then activate the 3-d camera option. Using the rectangle tool, you "build" a back wall, then switch to the top view and draw a rectangle for the floor, which you duplicate to make a matching ceiling. Switch to side view, draw one "wall", duplicate that, and use the x/y/z positioning "handles" to put the sides of your box into place. The virtual camera then can be moved around in the frame to play with the perspective. You can also distort the room surfaces to force perspective. Next add intermediate objects like the couch and adjust the amount of blur to suggest depth of field. Then you add virtual lights and light the imaginary room ( a step I didn't bother with here, and one reason the shading is so flat)

You can map actual photos to the wall and ceiling, if the perspective is good, and this will improve the realism quite a bit, along with the virtual lighting. This fast cartoon here is all I'm willing to do right now for no money:-)



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Marc Lucas
Re: Green Screen question
on Dec 6, 2012 at 10:23:01 am

That is a great little mockup I really appreciate the time and effort you have put in there!
What I didn't mention is that these clips are to be included into an existing TV ad that is all live action of the same kind of thing but at an actual house. The big problem is that they need to kind of look like they were taken at the same time as the original filming so to keep the realism up I was thinking just a narrow corridor for the BGs so the less you have going on the more possibility of blending in with the other clips etc.
I tried a Key in FCPX (same keyed as in Motion I believe) and I got really good results even though the crinkles and lightning wasn't that good. On the shot we only had very small spaces to work in thats why the lighting wasn't 100%

I'll have a go at the creating a 3D box scenario like you mentioned but just try it with a narrow corridor and see how that comes out. I was even thinking of having a go in C4D.

Again many thanks for you time I'll let you know how I get on.


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Mark Suszko
Re: Green Screen question
on Dec 6, 2012 at 3:29:10 pm

Probably your most important tool here will be these controls:



You get these controls when you invoke the 3-d camera in Apple Motion. Notice you can emulate a number of lens settings and then tweak the simulated depth of field, so when you place flat 2-d objects in the 3-d space, they will each blur by the proper amount, based on their distance to the virtual camera's focal plane.


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Stephen Smith
Re: Green Screen question
on Dec 10, 2012 at 10:09:33 pm

Looks like a fun project. I wouldn't bother with C4D. Still photos cut in layers like Mark talked about is cheaper and looks more realistic. If you have AE the keyer in that program is amazing!

Stephen Smith
Utah Video Productions

Check out my Motion Training DVD

Check out my Vimeo page


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Mark Suszko
Re: Green Screen question
on Dec 11, 2012 at 7:19:58 pm

So... did you make anything yet, Marc? We want pictures!


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Marc Lucas
Re: Green Screen question
on Jan 7, 2013 at 4:06:57 pm

Hi Mark

Here are a couple of grabs from the ad, the clips were only a couple of seconds long within the ad.

Window 1 was just a quick and easy flat wall in C4D and I added a 3D picture frame and an image I took in London. The second was a stock kitchen shot. The perspective makes the room look an odd shape but for the time the clip was on you don't really take that in.

https://dl.dropbox.com/u/2003727/Window_1.png

https://dl.dropbox.com/u/2003727/Window_2.png


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Mark Suszko
Re: Green Screen question
on Jan 7, 2013 at 6:46:03 pm

Those look great! I would make one small suggestion, either in C4d's render controls, or by using a filter in Photoshop or your compositing program, add some depth of field blur to the back end of the kitchen and to the painting on the wall. Right now you have every inch front to back in perfect sharp focus and that looks unnatural, more so for the deeper shot with the kitchen chairs etc.

There's a trick where you can imitate the tilt-shift lens effect by stacking two identical stills together, adding blur to one, and then sticking another layer in-between this sandwich, comprising an alpha mask made from a simple gradient.

Or find a DOF effect filter plug-in and apply just a whisper of it. I think that will really help sell your illusion.


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Marc Lucas
Re: Green Screen question
on Jan 8, 2013 at 10:36:00 am

Yes I over-looked that but will take that onboard for next time!

Thanks for your help and comments!


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