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Keeping a darker shade of green in the foreground while green screening

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Steve Newnham
Keeping a darker shade of green in the foreground while green screening
on Jun 1, 2010 at 6:18:55 am

Hi to the keying experts out there,
I've been given some footage to key which is a green cereal box held up against a slightly lighter green screen. (Yes, I've requested them not to do this again-we have a perfectly good blue screen!) I want to keep the green product box but lose the screen by showing the hospital ward freeze in the back - predominantly beige and white. I have dvgarage's suite of keying apps-matte pro,match,screenfix & wrap - as well as everything in FCP 7. I can almost get it but the box is still semitransparent. http://i1.creativecow.net/u-upload.php#'>http://i1.creativecow.net/u-upload.php#http://i1.creativecow.net/u-upload.php# I've tried to upload screengrabs of the settings and result so far for your ref. - hope they work. I also have Color but haven't explored keying possibilities there yet. Grateful for any help you can give.

Cheers,

Steve

Steve Newnham
Knowledge Media Division
Deakin University
Final Cut Studio, Xsan, EX3/DSR450


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Shane Ross
Re: Keeping a darker shade of green in the foreground while green screening
on Jun 1, 2010 at 7:10:00 am

Color isn't a keyer.

Sorry, but whoever thought keying a green box against a green screen was a good idea is an idiot. No pulling punches here. I can't believe that the DP did it. Producers, I can see them not knowing the difference. But the DP also shows that he knows squat.

The only option you have is to rotoscope the shot. IN FCP, you can use the 4 or 8 point garbage matte and work frame by frame. In After Effects, gonna have to use mattes and rotoscope. Motion, AE, Shake...those are keyers. If you are a keying novice, then hire a pro, and be prepared to spend a lot of money.

Or reshoot. And this time, do it right.

Green on green... man that's laughable.


Shane



GETTING ORGANIZED WITH FINAL CUT PRO DVD...don't miss it.
Read my blog, Little Frog in High Def


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Shane Ross
Re: Keeping a darker shade of green in the foreground while green screening
on Jun 1, 2010 at 7:17:22 am

And before you get all bend out of shape about my attitude, I have seen seasoned professionals blow a hundred thousand dollar shoot day by shooting "white screen", thinking we can key out the white. Yeah, we did. Well, I hired someone who could, and it took a week and cost them quite a pretty penny, but less than a reshoot. And it looked OK, not great, but a lot better. But it took a pretty hefty FX house to do the work.

So even pros can be morons. Which is why you have a VFX supervisor on set when shooting, even green screen. Unless you know what you are doing. And anyone who wants to key green, and puts a green object in the shot...sorry, they don't know what they are doing.




Shane



GETTING ORGANIZED WITH FINAL CUT PRO DVD...don't miss it.
Read my blog, Little Frog in High Def


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Richard Sanchez
Re: Keeping a darker shade of green in the foreground while green screening
on Jun 1, 2010 at 7:37:28 am

You're definitely going to need to use a combination of roto and a darn good keyer. Fortunately, After Effects should be able to handle this. Unfortunately, if you've never used After Effects, this is hardly a first project type of project though you're welcome to give it a shot.

Even with the roto brush in CS5, you'll need a decent amount of contrast for the tool to roto out your foreground. First off, is there a lot of motion in the shot? If shot, a simple mask should take care of the bulk of it. Depending on how different the green on the box, and the green on the matte are, you might get away with using two or three instances of the built in color keyer, some spill suppression (though not much, so you don't affect the green on the box) and a matte choker.

Pete O'Connell, in the After Effects forums has some great DVDs and tutorials on roto techniques that might help you too.

Richard Sanchez
North Hollywood, CA

"We are the facilitators of our own creative evolution." - Bill Hicks


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Christopher Targia
Re: Keeping a darker shade of green in the foreground while green screening
on Jun 1, 2010 at 1:51:52 pm

A simple trick I use, (if the object does not have green edges) is to copy the video track and put it ontop of the keyed track, then crop out and/or garbage matte everything but the green part of the object. This works well if someone decides to be a pain and where a green tie, or a product has a green part of its label, however if your are trying to key out a watermelon you will be in trouble.


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cowcowcowcowcow
Mark Suszko
Re: Keeping a darker shade of green in the foreground while green screening
on Jun 1, 2010 at 3:57:13 pm

I've thought about this, and you already got the best conventional advice... and while roto or garbage masking is your best bet, there may be one other thing to try. Deliberately skew the overall contrast and color to an extreme, see if that enables you to pull a key, take the matte saved out from that key and apply it in between the good tracks.

If you exported a string of targas or tiffs to photoshop, you could use the color selection/replace tool in that to selectively change the green screen to blue screen, (or orange or any color but green), re-export it back to your timeline, then chromakey as normal. Might not be any faster than matting a rectangular object, unless there is a lot of motion in the scene.

Please try again to re-post a still grab of the shot; it would make suggestions easier.


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Jeremy Garchow
Re: Keeping a darker shade of green in the foreground while green screening
on Jun 1, 2010 at 5:17:48 pm

Your link does not work.


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