how to remove dark edges around subject after keying in After Effects
by Patrick Saad
on
Jun 11, 2008 at 3:44:56 pm
Hi my dear Creative Cow users,
I have a question to ask you. Related to keying using Keylight Plugin and After Effects CS3.
I am building a tiny studio (home depot made) at work and I will be filming an interview which will have the background keyed out.
I am using a tradeshow booth that has a blue carpet in the background
(see screenshot at: http://screencast.com/t/MyctNfqxA )
After setting up my 3 lights (1 in the back and 2 on the front right and left with a diffuser), I managed to kill practically all the shadows and light up my subject correctly.
After filming I imported the footage into After Effects CS3 and used the KeyLight by Foundry Plugin to remove the blue background.
I made sure to set the Clip black and white accordingly to have a good balance of transparency for the background
(see http://screencast.com/t/fni3Yt44 )
I tried playing with the settings for the keylight plugin to soften the edges but it makes the subject look too soften and blurry on the edges, not the effect im looking for. No matter what I do its either too blurry on the edges or there's that badly keyed out edge. I don't know what to do in order to remove that dark edge? Could this have to do with not enough lighting on the subject during the filming? Did you ever have to deal with that issue?
Re: how to remove dark edges around subject after keying in After Effects by Dave LaRonde on Jun 11, 2008 at 4:28:49 pm
I'm sorry to be the bearer of bad news, but once I looked at the un-keyed picture of the subject and background, there was no question in my mind that you were in trouble. Then as I looked at the keyed video, I was surprised that you were able to pull as good a key as you did. The good news is this: at least you ran a test, so you can fix things before the Big Day.
You were in trouble from the start because:
• Blue carpet isn't an adequate substitute for a real chroma key background. The color isn't a pure blue, it isn't saturated enough, and it has texture. Ideally, a chroma key background is flat and featureless, but yours is far from that.
• The background lighting is inadequate. You're trying to get one light to do the job of at least four. The lighting has to be even with no hot or dark spots. You have plenty of both.
• The subject is way too close to the background. Judging by the picture, I'd say there might be three feet between subject and background. You don't have any leeway to light the subject and background separately, which is essential. Once you get adequate light on the background, the subject will be inundated by background spill, which will make your keying job all the more difficult.
So what are your options now?
• Come up with a Plan B which does NOT involve shooting an interview subject on your current chroma key setup. Find an alternate location to shoot so you don't have to chroma key. This is the ABSOLUTE BEST alternative given your current circumstances.
• Shoot outdoors, putting at least 8 feet between subject and background. Use reflectors on the subject. Mr. Sun is known to be a very even source of light. When I shoot outdoors with a portable chroma key background, I angle the background so that it's shaded. There will be pitfalls to this plan: Mr. Cloud can give you fits if he decides to dart in and out, and if the wind blows, your background will almost certainly take on the aerodynamic characteristics of a kite.
• Build a bigger studio
• Get a real chroma key background
• Get at least four more lights -- with diffusion filters -- to light the background
• Google "chroma key", "chroma key lighting", "blue screen", "bluescreen" "blue+screen+lighting", etc. Read up on the requirements for chroma key for NEXT (not this) time.
Sorry to have to say this, but if you pursue your current path, you're heading for disaster.
Dave LaRonde
Sr. Promotion Producer
KCRG-TV (ABC) Cedar Rapids, IA
Re: how to remove dark edges around subject after keying in After Effects by Kevin Camp on Jun 11, 2008 at 6:21:53 pm
here's detonation films' recipe for low budget chroma green paint. but, as dave mentions, you'll need adequate lighting and a large enough room to have a decent amount of space between the subject and the screen.
Re: how to remove dark edges around subject after keying in After Effects by Maciej Sarna on Jun 18, 2008 at 8:09:11 am
Hi! This too late for sure, but maybe for some people still strugling with this problem might be useful.
Did You try "matte choker" after keying? This should fix the problem and cut theese edges out. I,ve done it many times with badly lighted blue/green screen and the results were satisfactory (relative). O! and I'm using the bild in AE filter "linear color key" insted of "keylight" - don't know which is better - writing this just to note.
Re: how to remove dark edges around subject after keying in After Effects by Chris Wright on Jun 11, 2008 at 7:17:44 pm
Here comes the "if you are broke rebuttle..."
You can use hard lights from hardware stores then diffuse them. You can use amber gells to cut down light spill if you don't have a large keyer. Outdoors works fantastic at a 45 degree angle to matte if you have no lights but use green for matching outdoors, because blue being keyed outdoors and indoors doesn't match saturation to itself.
and...
Upload a TGA, TIFF or BMP at the highest quality to an upload site and post link. I'll try keying it as a single image with Primatte Keyer. I have keyed worse for clients b4.
Re: how to remove dark edges around subject after keying in After Effects by Dave LaRonde on Jun 11, 2008 at 7:47:25 pm
[Chris Wright]"Here comes the "if you are broke rebuttle..." "
...and here comes the CYA rebuttal.
Pursue a chroma key if you reeeeally want to, but be prepared to shoot it TWICE: once on the key background, and once with an appropriate part of the real world in the background.
That way, if the key doesn't work, you haven't hosed yourself. And who wants to hose oneself?
Dave LaRonde
Sr. Promotion Producer
KCRG-TV (ABC) Cedar Rapids, IA
Re: how to remove dark edges around subject after keying in After Effects by Chris Wright on Jun 11, 2008 at 11:09:09 pm
This is how good primatte keyer is. I got this with a few clicks of the mouse, no photoshop. And this is with just a thumbnail! The full sized video would be even better.
