Question of Keying green screen in FCP

[Craig Whitaker]

Hi,

When pulling a key for a shot, the best two tools are time and patience. You already have the right software, just need a different approach. First, one instance of one keyer node isn’t going to work. Look at your shot. Where does it make sense to break it up….head, body, hair? Most likely, you will need to use at least two or more separate shapes for the final shot. Also, try thinking about one matte for the core of your object and another for the edges. Take the results of each and combine them together to make your final matte.

Best,
Craig

[George Mizzell]

Well, this might seem like a novice question but I know about the garbage mattes and set them up first thing and do some basic color adjusting to get it looking as good as I think it needs to look (I am not making a Disney movie). Then I use the basic color keyer with FCP and start adjusting the tolerance, thin line and feather. This usually results in about 90% acceptable. I tend to still see green tint in the hair and a dark line around the outline.

Are you saying that in addition to the garbage mask I can create more than one key or more than one mask and is it possible to create more than one key? I know I can just drag more keys into the viewer but I have not seen cummulative results. Please add a little more info.
Thanks
George

George Mizzell
The SupermagnetMan

[Mark Suszko]

What would really help is if you can use the Apple “grab” tool and the little photo icon on the COW page for your reply to snap a jpeg of the work in progress off your FCP screen, upload and post it here.

What codec are you working in? DV25 is a poor codec for chromakeying in, but most keying software has a handle on it by now. Still, you may find a codec with more resolution provides less aliasing and thus smoother key edges.

Have you tried using the “enhance” slider to add some magenta to counter the green edges? And the spill suppressor? Without seeing a still shot of the problem, my first guess is you have the green too bright and too much spill on the talent from being too close to the wall. In your small studio space, if you have enough room, put the talent at least their equivaelnt height, plus a foot, away from the green. If you don’t have that kind of room, hang a backlight with a magenta filter gel aimed at the head and shoulders of the talent, to help suppress green reflected spill.

Keying depends on very even lighting of the background. Assuming you have done that, chromakeying does not need the green to be neon-bright to work; instead, the more important thing is the amount of color saturation in that green. I have had amazingly good results in the standard FCP keyer for most of my jobs. The trick, for me, has been even lighting and enough chroma saturation to make it obvious and unanimous to the program which pixels we don’t want. Maybe try to over-saturate using the color corrector, just to generate the matte.

Failing that, a trick that sometimes can help with a bad key source is to do an extra step using luminance keying. Use the 3-way color corrector to deliberately exaggerate the image contrast so as to make your talent look like a black silhouette over bright green or white. Choke that key down by a pixel or two and use it as another masking layer thru use of blending modes.

You also got very good advice about combining multiple instances of the keyer to different areas.

[Craig Whitaker]

George,

If you have access to Shake, use it. Keying is FCP is fine if you have one shot to do, aren’t worried about detail and have great conditions.

Inside of Shake, you will be using multiple instances of Keylight (or whatever keyer you want)

The reason for this is that a subject in front of a greenscreen is going to have very different edges at different parts of their body. Focus on one part at a time. Take the head for example. Draw a rough shape around the head and focus on getting a key JUST for that. When you’re doing this, make sure you’re looking at the alpha channel in the viewer. Your goal at this point is to make a beautiful black and white image. Keep that in mind as you’re working on keys…black and white. Once you tweak the settings so you have a great black and white image for the head, move on to another body part.

At the end, you’ll have a bunch of black and white images that will need to be combined to make one master matte. In Shake, I think the best node to use would be a Max node? What that’s looking for is the maximum value of each pixel on the screen. If you’re dealing with black and white, obviously white will win. You’ll take the white parts of the head, combine them (Max) with the white parts of your body matte and so on and so forth.

The other aspect of this is the core/edge matte approach. Sometimes when pulling a key (often when pulling a key) you will get better results tackling edges and cores separately. Still think about black and white. Pull a key on someone’s torso for example. Just try and get the edges clean…don’t worry about the core. Ok so now you have a matte with beautiful edges but it’s probably full of holes. Black and white. Pull a second key and this time only focus on the core. The edges will look like crap but who cares, you already have an edge matte.

I hope this is all making sense, it took me a long time to get the concept of just making a black and white picture (some days I feel like I’m still getting it….I probably am, haha)

Would love to help if you need any other tips…my knowledge is limited but considering I acquired 90% of it on forums, I’ll help anyway I can.

Best,
Craig

Craig Whitaker
MFA Candidate
New York University
http://www.craigwhitaker.net

[George Mizzell]

Well I went through the steps for the uploading and have not received anything yet. Do you know where it goes or how many hours it usually takes for the site to send the link that I am to paste in the message?

Thanks again for your help. I can post the images on a web page if that helps.

George Mizzell
The SupermagnetMan

[George Mizzell]

1216_greenscreenedit1.tiff.zip

I think this is the link to the file. I brought this into FCP using the Apple Pro Res 422 HQ preset. I had been using the generic HDV preset. I was just trying it to see if there was a difference but I could not tell much difference.

George Mizzell
The SupermagnetMan

[Mark Suszko]

You need to get the embed code:

Malkovitch!

[George Mizzell]

Did you see the message with the link that I posted earlier today?

George Mizzell
The SupermagnetMan