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Possible to replace green screen without masking?

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Josh PigfordPossible to replace green screen without masking?
by on Jun 5, 2012 at 5:39:19 am

So here's what I'm working with:



What I ultimately need to do is replace that green screen with some video footage. But there are a few problems that make this not all that straight forward...

It starts off with nothing on top of it, but the photos are gradually placed around it (all while the camera is "swimming").

I'm tracking it in Mocha, no problem. And getting the corner pin data in there to properly place the footage is easy.

But what I'm having issue with is replacing that green screen footage so that the photos show up "on top" of the video. I've got the drop-in video on one layer, then the source footage on top of it and I key it out so the video shows up underneath it.

But if I just do a basic key on that top footage, I end up screwing it up because of all the tweaks I need to do to get a good key:



So, is there a way to do it, without creating a precise mask around all the green? The mask would have to be generated in Mocha, I assume, since all these photos are being laid on top of it...meaning I'd need to track them as well.


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Angelo LorenzoRe: Possible to replace green screen without masking?
by on Jun 5, 2012 at 6:44:18 am

Are you tweaking the key in hopes of keying the yellow tracking markers or are you using an inner matte/garbage matte? If not, give that a try and liberally dial down the strength of the key just for the green. That may give you a better automated key.

Yes, ideally you'd want to track holdout mattes for all the photos on top and then just concentrate on keying the edges of the green. What seems like more work now will probably be easier in the long run.


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Stefan HinzeRe: Possible to replace green screen without masking?
by on Jun 5, 2012 at 11:18:25 am

hey,

make a copy from the image and make a matte from that...
maybe using KURVE or COLORAMA to boost the colors (greens)
;)


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Roland R. KahlenbergRe: Possible to replace green screen without masking?
by on Jun 5, 2012 at 3:36:18 pm

There is no indication at all as to what the final framing looks like. There is also no indication how the photos will be placed - in post, on set and if on set how exactly will it be placed?

Your issue isn't difficult but unless you provide more details, it's near impossible to provide you with an efficient solution.

HTH
RoRK

Intensive AE & Mocha Training in Singapore and Malaysia
Adobe ACE/ACI (version 7) & Imagineer Systems Inc Approved Mocha Trainer


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Josh PigfordRe: Possible to replace green screen without masking?
by on Jun 5, 2012 at 3:39:34 pm

The final framing looks like that last screenshot I attached.

That's an actual shot from the footage I'm working with. The photos were placed on set as part of the shot. Photos were placed by hand as the shot progressed.

So, it starts off with nothing else on screen except that green card, then photos are gradually added to the shot by "actors" on set.


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Roland R. KahlenbergRe: Possible to replace green screen without masking?
by on Jun 5, 2012 at 3:54:52 pm

I doubt that what you've provided is the last frame of the shot. I am assuming that more photos will be placed onto the green plate.

I presume that the photos will be placed from top to bottom. Right now, I see a row at the top of the green plate. Will there be other photos placed further down the green plate? IOW, a hand will cross over photos already placed along the upper row?

Sorry Josh, but more info is required.

Cheers
RoRK

Intensive AE & Mocha Training in Singapore and Malaysia
Adobe ACE/ACI (version 7) & Imagineer Systems Inc Approved Mocha Trainer


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Josh PigfordRe: Possible to replace green screen without masking?
by on Jun 5, 2012 at 3:57:56 pm

No more photos will be placed onto the green plate. It is the last shot.

Photos are placed in random order and no hands cross over other photos.


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Roland R. KahlenbergRe: Possible to replace green screen without masking?
by on Jun 5, 2012 at 4:32:50 pm

Your issues are that the photos are not complete within the green plate. You should however be able to mocha-track each photo as it is placed into position.

A secondary issue is the shadow from a photo filling into a photo already on the green plate. Then again, it's not too tricky if you use mocha's edge width feature.

In terms of your Compositing Plan - the layer ordering, from top to bottom will be such -
1) photos
2) video insert onto the green plate area
3) original video (backing plate)

1) should be easy to track. can be enlarged by small amount to ensure that it covers the original video

2) track the green plate and then apply the corner pin data. if the green plate can be 'described perfectly via the corner-pin effect, then great. Otherwise, you'll need a mocha Shape Layer - which can be linked to the track.

No keying is required here.

3) Nothing to do here.

HTH
RoRK

Intensive AE & Mocha Training in Singapore and Malaysia
Adobe ACE/ACI (version 7) & Imagineer Systems Inc Approved Mocha Trainer


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Josh PigfordRe: Possible to replace green screen without masking?
by on Jun 5, 2012 at 4:38:14 pm

So on #1, are you saying I'd track the photos in Mocha, and then export the shape data to After Effects and key those layers just enough so I get the shadow data on the video inserts?


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Roland R. KahlenbergRe: Possible to replace green screen without masking?
by on Jun 5, 2012 at 4:49:08 pm

Do a mocha track. There is no requirement for a shape layer as the corner-pin data should be able to fully encapsulate each photo - shape layers are required ONLY if the area you want to export cannot be completely defined by four cornered points (aka corner-pin). This is the case if you do not need the shadows. If you do need the shadows, then the corner-pin will fall short because it lacks edge width adjustments. Use a Shape Layer and create appropriate edge width keyframes.

If it were me, I'd crop off the shadows and create all the shadows in post. Any photo with a shadow over it will be cropped, enlarged and shifted back close to its original position. Kinda extreme but then it's a lot faster.

HTH
RoRK

Intensive AE & Mocha Training in Singapore and Malaysia
Adobe ACE/ACI (version 7) & Imagineer Systems Inc Approved Mocha Trainer


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Jeff BrownRe: Possible to replace green screen without masking?
by on Jun 7, 2012 at 1:44:34 pm

I'd don't think this was suggested:

Use your keyed FG layer as a track matte for an un-altered, un-keyed FG layer. Still might have to fuss with some shadows, though.

-Jeff


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