Keying out Green and Blue in the Same Shot

[Michael Gossen]

How about precomposing after the first key?

Michael Gossen
Helium Digital Media

[Eric Goldstein]

Hi Michael,

Thanks, precomping the first key solved the problem.

Eric

Eric Goldstein
Giraffe Film Company
Los Angeles
eric@giraffefilm.com

[Eric Goldstein]

Hey Michael and anyone else. Let me ammend my response. Precomping the first key helped, but didn’t entirely eliminate the problem. The Greenscreen and the blue tracking marks are well lit. But, even precomping the green key, the later blue key forces the edges of the main key to become rough in order to totally eliminate the blue tracking marks.

Any other ideas?

Thanks,

Eric

Eric Goldstein
Giraffe Film Company
Los Angeles
eric@giraffefilm.com

[Joey Foreman]

No blue in your subject, right? Give this a shot. Key the greenscreen, but lose the keylight for blue. Now duplicate the layer. On the top layer copy, delete keylight, and apply a Hue/Saturation effect. Switch this to blue channel. Now apply a Shift Channels effect. Solo this layer and change the comp view to alpha.
Now on the shift channels effect switch everything to Red. Now on the Hue/Saturation effect boost the blue saturation and decrease the blue lightness until the markers have vanished – turned pure black – in the comp window alpha view.
Unsolo this layer and turn on the Alpha Track Matte for the layer below. Switch the comp window back to RGB.
Did it work?

Joey Foreman
Editor/Animator
Nowhere Productions, Athens, GA

[Eric Goldstein]

Hi Joey,

Perhaps I’m not doing it properly. I followed your directions, but got a very transparent version of my foreground scene.

Any thoughts?

Thanks,

Eric

Eric Goldstein
Giraffe Film Company
Los Angeles
eric@giraffefilm.com

[Joey Foreman]

The idea is to have the blue markers in the top (matte layer) pure black in the Alpha view, and the subject pure white (except for edges.)
Solo the top layer again – turning off the track matte on the layer below first, then mouse over the comp window (in Alpha Channel View) and watch the info palette. The background area and the markers should read 0 – pure black, and the subject 255 – pure white. If you aren’t getting these values you can add a levels adjustment to the matte layer, and push the outer triangles in until you have pure black and pure white.
Then unsolo the layer, turn it off, turn the alpha track matte back on for the layer below, and switch back to RGB view in the comp window.

Joey Foreman
Editor/Animator
Nowhere Productions, Athens, GA

[David Bogie]

It’s usually easier to just put masks around tracking markers. They can be tracked if absolutely necessary but simple keyframes should be able to do the chore in most situations.

You can google using tracking markers and find interesting help. It’s a popular technique.

bogiesan

This is my standard sigfile so do not take it personally: “For crying out loud, read the freakin’ manual.”

[Michael Gossen]

Yeah,

Realistically, it would probably take you much less time to matte them out. Depending on your footage and the size of the trackers, you might be able to expand your key a little bit to overflow those areas…if they are too big in the frame, or you are lacking resolution, it might start to break down. I am sure it would be nice to key everything and walk away, I don’t know if I have ever had an easy key, just an easier one… Sometimes a little elbow grease goes a long way. Good luck.

Michael Gossen
Helium Digital Media

[Patrick Hearn]

What I’d do is duplicate the layer. On one do the green key, on the other the blue. Now alpha matte the green by the blue. Hopefully that should do it.

You might possibly have some specks left over. Do junk mattes before keying and perhaps blur the blue layer a little after the key.

[Eric Goldstein]

Thank you all for your thoughts. In the end it’s probably going to be a little of all the solutions mentioned. I’m going to try to avoid masking as much as possible. I’ve been playing around with multiple layers, but so far haven’t gotten a better result than using two keys on the same layer, but I’m still working on it.

The thing that’s hurting the key is that the blue tracking marks were made using blue tape. Even though it’s very slight, there’s a slight edge and therefore a very slight shadow around the tracking marks. It’s this shadow that causing what would otherwise be an easy key to be problematic.

Thanks again,

Eric

Eric Goldstein
Giraffe Film Company
Los Angeles
eric@giraffefilm.com