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Issues with Keylight

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Jason Mann
Issues with Keylight
on May 2, 2010 at 3:26:51 pm

Hi all. I'm hoping someone out there can help me figure out if I'm shooting my greenscreen footage wrong or somehow screwing it up in the FCP Keylight plugin. (I can't make it look good in Motion either...)

Here are three sample shots of our interview setup. (Details: HPX-170 at 720pN, KinoFlos lighting a fabric screen and the subject).

As soon as I pick a screen color in Keylight, I get nasty jagged edges and dark outlines around the footage. I've used Keylight in AE as well (unavailable to me on location, where I need to do this work), and had the same issue.

So, is this screen too dark/light? Not saturated enough? Is the subject not backlit enough? (God, I hope not!) I'm trying to go very easy on adjusting the screen matte settings in Keylight, to avoid crunchy edges, but I can't seem to find a winning combination. Help!

Here's an example of the bad edges:

All I've done at that point is picked a screen color (from right to the right of subject's face.) ARGH! Those edges look horrible!

Setup 1, (screen is fairly dark)
Setup 2
Setup 3, boosted the level of the screen, thinking that would help. (It does seem to be more saturated on the HPX-170's vectorscope, but I'm still getting crunchy edges immediately on picking a screen color.)

Just for the record, in AE I always try to use multiple instances of Keylight to get a good key. And I realize that's better. But shouldn't I be able to get something halfway decent from this footage in one pass?




--
Jason Mann
Compass Light, Inc.


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matthew bradshaw
Re: Issues with Keylight
on May 3, 2010 at 6:43:28 am

This is what I got with one click in AE using your version 3 ... http://www.beermattonline.co.uk/3_00040.jpg Your jpegs are pretty noisy so it is hard to tell. What format is your footage?
Matt



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Jason Mann
Re: Issues with Keylight
on May 3, 2010 at 8:33:11 am

Thanks Matt. It's DVCProHD, 720pN, shot on a HPX-170. I don't really know why it seems so noisy. Other people don't seem to have this much trouble getting keys from that codec.

I think I may have underexposed the subject slightly, maybe that is contributing to it. (But that's just a total guess.)

Also, I'm using daylight balanced Kino tubes on the screen and subject. (Hopefully that isn't the problem, because I'm on location now, and can't easily get tungsten tubes.)

Detail level, vertical detail level in the camera are all the way down. Detail coring is at 0. I'm thinking of cranking that way up, but doubt if it will make much impact. (According to the Barry Green book, coring is more noticeable at controlling noise when detail level is set high.)

The vectorscope in the HPX-170 shows the dot that represents the screen right in line with the green target. Not that far out toward it (meaning it's not that saturated) but it's at least halfway out.

I'm at a loss.

--
Jason Mann
Compass Light, Inc.


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matthew bradshaw
Re: Issues with Keylight
on May 3, 2010 at 9:24:33 am

Hi again. Are you keeping it in that codec when you put it into AE or FCP? I know we had problems keying dvcpro 50 green screen that came from digibeta and had much better luck in other codecs. If you wanted I could have a bash at a short clip. You can contact me direct through my site ... beermattonline.co.uk
Matt.



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Jason Mann
Re: Issues with Keylight
on May 3, 2010 at 9:32:22 am

I am keeping it as DVCProHD (or have been so far). Just using Log & Transfer to bring the footage into FCP, then straight DVCProHD sequences.

If I understand you right, I should try:
1. Making a new sequence, setting it to ProResHQ or Animation or something like that, at 1280x720, square pixels.
2. Adding clips to that sequence
3. THEN running Keylight on those clips.

Did I get that right?

I will give that a shot, anyway... Thanks so much for helping with this.

--
Jason Mann
Compass Light, Inc.


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matthew bradshaw
Re: Issues with Keylight
on May 3, 2010 at 9:48:40 am

I don't think you will get any benefits from converting it to another codec. You want to make sure that you aren't compressing it any more than it already is and if your sequence format is the same as your capture format then I don't think you are. Feel free to send me a short clip, I'm grading a short film today and could do with a break!
Matt.



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Dave LaRonde
Re: Issues with Keylight
on May 3, 2010 at 4:24:57 pm

I'm not trying to be disrespectful here, I'm just trying to eliminate a potential cause of your problem.

I have never, EVER had problems getting a good key from DVCPro HD footage if it's well lit, and your Setup 3 looks fine. So I have to ask: are you trying to use Keylight intuitively without having run the tutorials?

There are a TON of adjustments you can make in the plugin, and they can help you if you know what you're doing or hose you if you don't.

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


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Jason Mann
Re: Issues with Keylight
on May 3, 2010 at 4:32:06 pm

No offense taken, whatsoever, Dave. In fact, I'm assuming it IS user error (or lighting error) on my part. I have read and re-read The Foundry's user manual many times. I've also used a great Keylight tutorial from Toolfarm (the name escapes me) that helped me learn the basics of using multiple instances, core mattes, etc in After Effects.

The only disappointing thing is that I thought I had lit this greenscreen better than my previous attempts.

That said, after some help from Matt via email (see above, and thanks again Matt!), I'm having a little more luck. And I think maybe my idea of what does and does not constitute a good vs. a perfect key was a bit off.

--
Jason Mann
Compass Light, Inc.


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