greenscreen help please

[Chris Zwar]

Good keying is not neccesarily easy, but if you want to take the optimists’ point of view then working with difficult keys will give you a lot of experience.
I like Keylight and think it’s great, and if you haven’t read the manual that comes with it (as a PDF) then that’s a good place to start. It’s very helpful. And when you’re keying with Keylight, use the “status” setting- it is invaluable. Look it up in the manual.

If you’ve done all that, then it sounds like the next step is to play with the matte chokers. AE has 2 in the “matte tools” area- the simple choker and a more complex version called “matte choker”. They’re extremely useful and just this week the AE matte choker saved some footage I thought was un-usable. When you use them, try viewing the alpha channel in the main composition so you can see exactly what they’re doing.

Beyond that you start to get into more complicated territory and 3rd party plugins.

A really complex key might involve the following steps:

1- degrain the source footage, and if neccesary, de-interlace it too with a 3rd party deinterlacer like fields-kit.
2- use the HSL filter or another colour correction filter to enhance the key colour in the background
3- use something like Pinnacle Composite Wizard’s “smooth screen” plug-in to even out the background.
4- use masks to create a garbage matte around your main subject matter.
5- key using keylight, which is the best keyer which comes with AE.
5b- for very complex keys, masking the source into multiple pieces with individual settings tweaked for each piece.
6- removing specks or holes in the matte if keylight hasn’t done it for you
7- cleaning up the edges of the matte with a choker or matte feathing plug-in or both
8- hand painting difficult bits frame by frame
9- removing spill with a spill suppressor

Check out the “Composite Wizard” which is sold by Red Giant Software, there are other equivalents too by other vendors but I can’t think of any just at the minute.

Hope this helps, keying is unfortunately not as easy as it should be!

-Chris

Motion Graphics Designer
Will animate for food

[Kierra Parlagreco]

Thanks for your tips. Since greenscreen stuff seems so prevalent, clients think it’s a one click deal. And that begins to make me think that I just don’t know what I’m doing! I tried much of what you suggested but not all, so thank you very much for the comprehensive check list. I do have DV Garage as well and maybe will try with that again.
The footage, by the way, was shot on Beta SX and transferred to Beta SP. To the eye it looks very clean but in reality not so much.
Anyway, thanks again!
Kierra

[Annaël Beauchemin]

i’ve also experienced this edge problem with Keylight. Footage was shot digibeta, captured 1:1 in avid, then imported in AE.

In my opinion, either there is a problem in the avid to AE workflow, either Keylight has a tendency to give problems with edges. There are a few pos about this in the forum if you search.

The only real solution is to add chroma blur to your footage. For this, you either use a third party chroma blur plugin (Sapphaire has one, Magic Bullet a better yet slower one) or then you use a series of AE filters: Channel combiner (set to YUV to RGB), Channel Blur (on green and blue), and then another Channel Combiner (YUV to RGB). And then your keyer. This AE methode seem to me a bit less effective, but much beter than without any blur. Why does clean digibeta footage requires chroma smoothing, I don’t know.

I’ve had better luck with combustion’s keyer, even tho it takes more time to get the key done there. Keylight is great because i really find a good key on the first click and it despill automaticaly, whereas your need t do it manualy in combustion and it takes more time and experience. But the edges definately are more “stable” using other keyers than Keylight. I wonder if there’s a bug in the bundled version of keylight.

[Peter O’connell]

primatte is good

[Jonathan Alexander]

Chris,

Thanks for your lengthy list of directions. Just curious, how does one “degrain” their footage as you have said in your step 1? I want to fool around with some footage and test your steps, but not sure how to start off by doing the degrain thing. Please help! Thanks, I appreciate it, keying has always been that one thing that just frustrated me too much to really get down and dirty with it.

–Jon

[Chris Zwar]

Firstly, for the sake of discussion, I have 2 3rd party degrainers. There’s one which comes with Pinnacle’s Composite Wizard, which basically checks a series of frames and averages them together if they’re similar enough. This is called temporal filtering, because it works with sequences of frames over time. Although the Pinnacle one is very useful, it can be harsh and I only use it with very subtle settings. It can also introduce artefacts in footage with fast motion, although with talking heads in front of a bluescreen this is not a problem and it can be very effective. It’s very quick too.

I also have Tinderbox 1, which has a degrain filter that doesn’t work across several frames (it’s a spacial filter), only 1 frame at a time. The manual says it is based on a median filter, so I assume it looks at a group of pixels which surround each other and looks for pixels which fall outside the calculated average range. I’ve hardly used it, and once again it can do weird things to footage but in this case not with fast movement but fine details.

Finally, since AE 6.5 the great folks at Adobe have included a filter simply named “Remove Grain”, which you’ll find under the “Noise & Grain” menu. This used to be a very expensive 3rd party piece of software and getting it free with 6.5 was a huge bonus. It is a fantastic grain removal tool but slow. The best thing to do is read the help files, but it’s worth noting that the filter does both Spacial and Temporal filtering, but temporal filtering is turned off by default. You can manually set it up to analyse different areas of your footage and it will degrain the result accordingly.

The “Remove Grain” plugin is not a trivial filter, it will take a bit of effort to get to know it, and some playing around to get the best results. But it is a serious tool and worth the effort. A few years ago now I “rescued” a bluescreen which had been shot on 16mm film, largely with this filter. While film presents very obvious grain problems for keying, video footage benefits immensely too- especially dodgy DV footage or low-light high-gain stuff.

Hope you have fun playing,

-Chris Zwar

Motion Graphics Designer
Will animate for food

[Steve Roberts]

With the Remove Grain effect, you should switch on “temporal filtering”. I used to demo the product when it was a third-party plugin, and that’s one of the things I retained. 🙂

Steve