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DV Green Screen Shoot

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Aaron Cadieux
DV Green Screen Shoot
on Dec 17, 2010 at 6:31:16 pm

Hello Everyone,

I am currently editing a commercial that was shot in a green screen studio. Depsite my objections, the commercial was shot in SD on interlaced DV. I would have preferred XDCAM or even DVCPro50 (as everyone knows DV is NOT ideal for keying). Just an FYI, I did not shoot this spot. I've been slaving over this footage for days tweaking it like crazy in an effort to make it as clean as possible. I've had good luck with the "color range" tool in After Effects. Keylight's results were too grainy, and Ultra CS3's results were sub-par. I've done as much spill supression that I can but you can still see hints of green in the shots. My boss (who insisted on shooting this in SD on DV) is complaining that the spot looks fake. I think the problem begins with the cartoon-ish virtual set he selected for the job. Do any of you guys think I will get results that look any better than this, or have I reached the end of the road for what keyed DV footage can look like? Any suggestions are greatly appreciated. Link to rough cut of the commercial below.







Thanks so much,

Aaron


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Michael Kammes
Re: DV Green Screen Shoot
on Dec 17, 2010 at 6:40:54 pm

Why not cross convert the DV footage to another codec before attempting to pull a key?

DV isn't that good for keying (as you know). DV50 is a bit better, and even 'fatter' codecs like Pro Res (if on a Mac) would work much better than DV.

I agree, the virtual sets do look cartoonish, plus the lighting of the subjects doesn't really match the 'set' lighting. The contestant shadows also look pretty fake, IMO.

Good Luck!

~Michael



.: michael kammes mpse
.: senior applications editor . post workflow consultant
.: audio specialist . act fcp . acsr
.: michaelkammes.com


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Aaron Cadieux
Re: DV Green Screen Shoot
on Dec 17, 2010 at 7:02:55 pm

Michael,

Thanks for your input. I have since removed the shadow effect. I was trying everything I could think of to try and make the keys look more "realisic", but obviously the shadows didn't do the trick.

Your suggestion about converting the DV footage to another codec is interesting. But detail that's lacking in the DV footage is still going to be lacking in another codec, correct? Wouldn't it be like if you took your favorite old TV show on a poor-quality VHS tape and then transfered it to DVD? The show is now on a better format, but the show will still look as crappy as it did on the old VHS tape. It's impossible to bring back detail that wasn't there to begin with, no?

If I do convert to another codec, do you think I will see that much of a marked improvement?

I wish people had listened to me to begin with, and none of this would have been an issue. My boss overruled both me and the shooter. Out of the three of us, he is the least tech-savy, and knows nothing about different codecs and formats.

Anyway, thanks for your advice Michael.

-Aaron



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Michael Kammes
Re: DV Green Screen Shoot
on Dec 17, 2010 at 8:06:52 pm

One thing to remember is color space.

DV has a color space of 4:1:1. DV50 & Pro Res are 4:2:2. Due to the low chroma resolution, DV is not very optimal for pulling a good key.

DV50, FYI, is a great alternative for broadcast quality, and many broadcast outlets who do SD still use it.

~Michael



.: michael kammes mpse
.: senior applications editor . post workflow consultant
.: audio specialist . act fcp . acsr
.: michaelkammes.com


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Mark Suszko
Re: DV Green Screen Shoot
on Dec 17, 2010 at 9:11:08 pm

AAron, couple things.

First, dude: you have GOT to stop bad-mouthing your bosses where they can google it. Frame the problem without the side-issue of your interpersonal problems, as it has no effect on what answers we can come up with for you.

Now, to your tech problem.

Those shadows were the wrong size and angle and didn't agree with the suggested dimensions of your set. Glad you already figured this out yourself, but maybe you should put them back, only, offset them way lower and fainter, and angle them to look like they are cast 180 degrees from the original key lights on your talent. On the very wide shot, you need to add a floor shadow effect to the floor around the host. Use his key matte or just blur an oval and warp it. It will "read" as his shadow just fine since he's not walking. One of the things that sells a chromakey is motivated-looking lights that are consistent in angle and quality between the new set and the green set.

Make that set softer in BG and imply shorter DOF by applying more gaussian blur to the set whenever you go to closeup shots of the folks, and less when the shots are wider. This effect mirrors the real-world physics of the shots.

Your contrast ratio doesn't match the set; the host particularly is over-bright compared to the backdrop. Bring up the levels on the BG and lower them on the talent, meet somewhere in the middle.

Your set design is hokey, but perfect for the context of the spot and copy. It has the right feel for a "The Price Is Right" cheezy game show aesthetic. But your host talent is over-lit and too bright. Try some 3-way correction on him.

I understand your metaphor about moving the project to a 4:2:2 color space but still being stuck with 4:1:1 footage. You put the same amount of water in a bigger bucket, so what's the difference? Well, same water, but now you can "swirl" it more:-). But believe these other guys when they say that the footage is going to key easier. Also your other graphics will be cleaner if you don't use DV.

Let's work on the keying. With DV green footage, it often helps to do multiple iterations of the keying process and stack up the mattes to build a better overall effect. This way each sub-matte can concentrate on one area and make fewer compromises.

I take it you already applied the spill suppressor filters that add magenta against the green. If not, try that now.

What I would do myself in this problem is, use the 3-way color corrector on the original green footage and deliberately accentuate the contrasts and the chroma values before trying to apply the key. The first goal is not a perfect skin appearance but a clean matte edge. When you have achieved the matte, you can stack that in the timeline as a masking layer and use blend modes. The matte will block for you and then you can make a separate layer with the 3-way color corrector used to make the subjects look their best, yet not affect the key. You can even turn that green screen blue with the 3-way CC and see if the keyer likes that better, just to generate the matte with.

When all else fails, you can always brute-force this by using photoshop as a rotoscoping tool. This is not as scary as it sounds, because photoshop has a great tool that speeds this up, plus you can create a batch action to treat a lot of frames in a short time. You will be able to roto an entire 30-second bit before you use up a 6-pack of Red Bull. Here's (roughly) how:

Take your green screen footage and export a .tif stills sequence to a folder. Bring the folder into Photoshop. Open the first still. Go to Filters> Extract. A custom workspace for the filter opens up. Find the teeny check box in it, top right, that says "smart highlighting". This next part is COOL. Make the brush relatively large, thick, and sloppy like a blunt whiteboard marker, and just freehand a quick and sloppy outline around the guy, the main point is to try to keep the line half in the green and half on the edge of the man's body. Now select the fill bucket tool within this filter's workspace (top left) and tap it inside the closed circle you just made. You should see a funky color outline and a contrasting color fill inside. Next hit the Preview button on the top right and call yourself a genius. You should be seeing a clean alpha matte of your guy. Sensitivity controls can be adjusted to detect the edge between subject and green backdrop. If the matte isn't perfect, you can still adjust it with the toolbrushes right in the filter interface, adding back edge or taking it away. You can even apply some other filter effects at this stage, like a border of soft magenta to counter the green spill. Save the frame.

Do these steps for 3,600 or so more frames. Hey, it's billable time to fix what the clients and boss insisted on. The results are good.

You can speed this up by creating a macro or automation within Photoshop. Learning how to make those is outside the scope of what I'm telling you here, you can look it up, but basically, you open up the first image in the stack, turn on the recorder function in photoshop, perform the steps you will be repeating a lot, all the way up to re-saving the treated frame over itself in the same folder. Turn off the recorder, name and save this as an *action*. Then apply the action in batch form to the images in the target folder. What I did the last time I had to roto a project like yours was, I built the Photoshop action to call up the frame, bring in the filter, let me apply it, then save and close the image and bring up the next one automatically. I churned thru a 30-second hunk of frames in about an hour. The way I did this before discovering batch actions, same job took three DAYS. You can save these batch actions and re-use them.

Yes, batch actions are your FRIEND.

Go try these and report back when you can; we'll all help you as much as we can.


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Aaron Cadieux
Re: DV Green Screen Shoot
on Dec 17, 2010 at 9:39:04 pm

Mark,

Thanks for the advice. I will try some of this when I get back to the office on Monday. An over-contrasty base matte is a cool concept, which will help big time. The photoshop rotoscoping sounds interesting, but due to time contraints on this spot, I won't have time to do it, but I'll bookmark this post for later work.

As for your first line of criticism, when I get canned, and when I can't get another job because of my Google history, I'll have only myself to blame. All of the people on the Cow can then shoot me a unified "I told you so".

Your advice and advanced expertise is greatly appreciated and admired.

Thanks again,

Aaron



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grinner hester
Re: DV Green Screen Shoot
on Dec 19, 2010 at 4:08:39 pm

Some folks just looove to save a tiny bit of budget shooting so they can multiply their budget in post. Keylight in AE will be your buddy in this case. A helpful hint for render times, if you use a regular color keyer first, you can remove much info that keylight would have had to do. Add it after the color keyer(s) and you'll save a lot of time.



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Dan Archer
Re: DV Green Screen Shoot
on Jan 3, 2011 at 11:12:29 pm

I think overall your boss is asking you to polish a turd. I have seen many time the boss come in and shoot on his DV cam and then wonder why it does not look like Avatar. Good luck

A cut is a cut & a dissolve is a disolve, and not just anybody with a system is a pro.


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