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Green Screen question

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Marc Lucas
Green Screen question
on Mar 28, 2012 at 3:25:52 pm

Keying some recent green screen footage. The greens were not lit as well as they could of been but still not bad results. I'm using dvGarage DV Matte to do the keying. I'm getting on well but one of the problems I'm having on one of the clips is that after I use screen fix to get the key as good as it can be and then putting on Matte pro plugin. I'm finding traces of white lines around the talent. After the initial key and tweaking the black & white points then adjusting the high & low points I get a quite convincing key. Then playing through the footage I see short white lines around the edges of the talent can't seem to get rid of them. I have tried adjusting the V & H blur controls but if I go to far on the setting then I see the white lines. I'm also seeing jagged edges around the talent. I am using 1920x1080i footage in FCP6. Any pointers to getting this better?
Thanks


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Mark Suszko
Re: Green Screen question
on Mar 28, 2012 at 7:09:23 pm

Can you use the grab tool to capture a screenshot of the problem, and post it here?


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Marc Lucas
Re: Green Screen question
on Mar 28, 2012 at 9:51:57 pm

Hi

You can see the problems here http://www.marclucasmedia.com/mattes/

Many thanks for any advice!


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Dave LaRonde
Re: Green Screen question
on Mar 28, 2012 at 10:00:41 pm

Oooh, the stinky color resolution of HDV or long-gop codecs rear their ugly heads!

You may want to consider masking this shot off into pieces like Head, Shoulders & Torso, etc. and pulling the key on each separately. That way you can choke the shoulders a little bit more without affecting the head.

Dave LaRonde
Sr. Promotion Producer
KCRG-TV (ABC) Cedar Rapids, IA


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Marc Lucas
Re: Green Screen question
on Mar 28, 2012 at 10:08:19 pm

It's XDCAM footage.

I'm using dvGarage matte suit so when you say 'choke' do you mean blur the edges to try and blend the hard edges more? Because I have horizontal and vertical blur controls.

Is the footage problematic because it's also inter-laced? We usually shoot progressive but for this job we had to use 1080i because of the camera the shooter shot on. For the future whats the best footage for keying?

Many thanks


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Dave LaRonde
Re: Green Screen question
on Mar 28, 2012 at 10:15:40 pm

That plugin has to have more control than just blurring, there ought to be a way to pull the shoulder edges in a bit, making them smoother. That's called choking.

I've pulled fine keys on interlaced footage; interlacing isn't the problem.

Do you happen to have Keylight by The Foundry? Does a fine job.

Personally, I like a camera that shoots in the DVCPro HD codec: it has better color resolution than most cameras, but doesn't break the bank.

Dave LaRonde
Sr. Promotion Producer
KCRG-TV (ABC) Cedar Rapids, IA


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Marc Lucas
Re: Green Screen question
on Mar 28, 2012 at 10:29:38 pm

Yeah I have Keylight 1.2 as part of AE but was doing this project in FCP6 so might have to do the whole thing in AE now then. The software hasn't got a choker but have just tried a Nattress choke plugin and hasn't done that much to be fair. I think I will have a go in AE to see what I come up with.
Many thanks for your comments!


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Chris Tompkins
Re: Green Screen question
on Mar 30, 2012 at 10:15:05 pm

+1 on Keylight in AE, will do wonders for you.

Chris Tompkins
Video Atlanta LLC


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Marc Lucas
Re: Green Screen question
on Mar 30, 2012 at 10:20:30 pm

I will give the Keylight a go over the weekend. Would it make any difference in converting to ProRes first will it make the footage more keying friendly (losing the jagged edges a little?)


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Chris Tompkins
Re: Green Screen question
on Mar 30, 2012 at 11:00:41 pm

I wouldn't, you can't rez up. You'll loose a generation actually, albeit slight.

Chris Tompkins
Video Atlanta LLC


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Dave LaRonde
Re: Green Screen question
on Mar 31, 2012 at 4:50:24 pm

I'm with Chris on this. For keying, there really isn't a way to improve the footage once it's shot.

It tough to overcome long-gop codecs plus bad lighting. Two terms come to mind: "silk purse" and "sow's ear".

Dave LaRonde
Sr. Promotion Producer
KCRG-TV (ABC) Cedar Rapids, IA


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Marc Lucas
Re: Green Screen question
on Apr 2, 2012 at 10:03:22 pm

I'm using Keylight to key the footage. All the tutorials I've seen have the Screen gain at the default of 100% and when they select the green to be keyed the back ground disappears and the e.g the talent or foreground element keeps all its colour and tonal quality. When I do the same thing I seem to be getting noise in my subject (gain noise I think??) With that I'm losing definition in colour and contrast detail. Why is this is it just because the default gain is to high?
If I then drop the screen gain I start to lose the transparency of the green.

If I go to screen matte view I can see clear contrast between the white & black areas but then going back to the final result view my talents clothing has lost the detail.


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Dave LaRonde
Re: Green Screen question
on Apr 2, 2012 at 10:12:52 pm

Sounds like the background was too hot for the subject.

Tell you what: If you're in After Effects, use Keylight to pull what should be a good-looking key, according to the Status view: white at the core, black on the background, grey around the edges. Change the view to final output.

Now duplicate the layer and REMOVE Keylight from the lower layer. Use the upper layer as an alpha matte for the lower layer. Got spill? Use AE's Spill suppressor, perhaps multiple instances.

With all the grief this shot has given you, I bet you never, EVER take proper green screen lighting for granted again.

Dave LaRonde
Sr. Promotion Producer
KCRG-TV (ABC) Cedar Rapids, IA


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Marc Lucas
Re: Green Screen question
on Apr 2, 2012 at 10:24:45 pm

I'll give that a go and report back!

Just out of interest I tried the footage in FCPX and it pulled a great key right off the bat, well impressed! Even the harsh edges have come out quite clean! I have also seen a technique for putting a 'light wrap' around the talent to help with blending into the BG so I might just export the keyed footage from FCPX and do the rest in AE.

The lighting was done by someone else on this occasion BUT yes I will definitely make sure that is sorted properly in the future. So I take it that because the green screen was lit to bright that the brighter colour information has affected and spilled into the talent thus resulting in the key not performing as it should?

Really appreciate your help on this one!


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Dave LaRonde
Re: Green Screen question
on Apr 3, 2012 at 8:15:41 pm

[Marc Lucas] " I take it that because the green screen was lit to bright that the brighter colour information has affected and spilled into the talent thus resulting in the key not performing as it should?"

Correct.
In still photographer's lingo, Keylight likes its backgrounds 2 stops under the brightest part of the subject.
In TV engineer terms, keylight likes its backgrounds at about 65-75 IRE on a waveform monitor after you've irised the camera properly.

A certain amount of spill light is virtually inevitible. You can invisibly negate bit of it with a very light magenta gel on the subject's back light.

Dave LaRonde
Sr. Promotion Producer
KCRG-TV (ABC) Cedar Rapids, IA


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Tom Sefton
Re: Green Screen question
on Apr 20, 2012 at 10:22:19 am

+1 for Dave's Keylight advice about using the source monitor and clipping the black and white levels.

If this doesn't work try masking off quadrants of your subjects body and keying each individually.


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Chris Lehmann
Re: Green Screen question
on Apr 13, 2012 at 8:26:29 pm

I can't see the video anymore but I have to say that DVmatte Pro is actually a very good keyer and is exceptional at handling less than ideal codecs and lighting. Are you dropping your background into the plugin or just as a layer underneath it in the timeline. You will get much better results doing it in the plugin.


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Marc Lucas
Re: Green Screen question
on Apr 29, 2012 at 4:34:08 pm

Thanks for the advice on this thread!

I tried with both Keylight & dvMatte pro and ended up using dvMatte.

The situation I was in was less that ideal the original footage had the green screen lit to bright ( I later found out that this was a result in there being to different shades on 'green screen' so they had to light brighter to compensate for this??)
I wasn't happy with the 'edges' I got originally with dvMatte so when Dave suggested Keylight I gave that a go to. When I initially tried Keylight the first key I was getting was taking way to much detail from the talent and making things difficult. I also tried Dave's suggestion of duplicating the layer and matting out the keyed footage with the original. That kind of worked but I wasn't getting the results I wanted/needed.
I thought why not give dvMatte another go, I perservered and actually got a really good key right out of the box....way better that the Keylight key! My main problem was the edges I had but with some tweaking and patience I got a good end result.

In retrospect I like the ease of use that dvMatte has it is a very simplified way of working with only a handful of options/controls that make the keying process really quite easy. I on the other hand would assume that the deeper I get into keying and the like the functions of Keylight with enable more flexibility for more complex workflow.
This was a great learning curve and can't wait to have another go! I think I'm going to download some stock green screen footage now and get more accustom with Keylight but for now dvMatte did a very good job for me and got me out of a hole!

Thanks for the comments and advice really appreciated!


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