Green screen jaggies

dlang

dlang

Well-known member
Ok I've read and watched all the incredible benefits of the ol' green screen shots, so I"ve finally decided to give it a shot. There probably is no real easy answer for this but, if any experts wanna give their advice.....First I'll tell you what's happening, then I'll tell you what I've tried to do to fix it. When I key I can get all blue gone accept for the hardest part around the edge. I know there is matte's etc to rid of the rim, but even when I tweak and get the blue rim almost gone there is still those funky jaggies happening. I use fcp and the keying filters, have read the article on ken stones site (good article) and it said to use the 4:1:1 color space filter first, so I've done this. OH I skipped some important details. I am using the bluest fabric I could find, have lit it up with a 1000 watt light with soft box, as even as i can. fabric has no wrinkles (had the wife iron, she's a pro) and my subject is sitting about 6 feet in front of the screen litt seperately. I must be missing something, so does anyone know how to get rid of the jaggies, or can explain why they're there. Thanks alot

D
 
try shooting as flat and pale as possible on camera. The more color bleeding you can avoid, the better. Also, from my own personal experience, blue is a lot less forgiving than green on DV. I've never actually worked with keying in FCP so I can't really help you on that front. Hope this helps.
 
due to the nature of what happens during anti-aliasing you're going to get an edge no matter which color you use. being that what's being recorded is being knocked down to 4:1:1 then the edge becomes a little more pronounced.

how to avoid it to some extent...

first don't light your screen brighter than your subject. a real bright light will cause a glare and make the bleeding more pronounced. i've seen some setups where they really didn't light the screen, but more so to even out the light that was hitting it from the other lights involved in the shot.

one thing that will truly benefit you is to light your subject with a strong kicker with an amber gel or amber color. that will suppress the green spill and reduce the edge around your subject.
 
I'm curious it there a lighting ratio for Green screen stuff. Or better yet at what IRE should the screen be lit, if the subject is at 80 IRE?
 
You are probably using a single 1/4 inch CCD camera. Once-upon-a-time I had the same problem. No matter how well I lit the blue/green screen, the final edges around the rim were a pain to remove since they left jaggies. I had to rotoscope almost five minutes of footage of my first short by hand!

Get a 1/3 inch 3ccd camera atleast. It wont elminate the problem, but make it easier to deal with. Keying DV is a pain anyway. HD is much easier.
 
novelt said:
one thing that will truly benefit you is to light your subject with a strong kicker with an amber gel or amber color. that will suppress the green spill and reduce the edge around your subject.
Click to expand...

He said blue screen, yes? So a magenta gel, rather than amber?
 
Get a 1/3 inch 3ccd camera atleast. It wont elminate the problem said:
Nope I've got a dvx100 and as we all know I'm sure that it has 1/3 inch chip. This has to be able to be done, I've seen some really well done green/blue screen done with the dvx. Keep em' coming folks I'm determined to figure this out. Thanks for all the replies so far

D
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Yes, but I think "green screen" has gone generic on us, easier to say than chromo-keying. :)

Like the "green room" back stage. Not necessarily green anymore.

From the original post: I am using the bluest fabric I could find, have lit it up with a 1000 watt light with soft box. . .
 
Where does ULTRA 2 fit in to all this and do the same lighting techniques apply? Is this a good or bad software for this?
 
genjerdan...i apologize :grin: :grin: :grin:

just re-read the post and that is funny. title "green screen"...post "bluest fabric"...funny that i missed that and tried correcting you when you were right or are we both right? :)

jon oskar...

the screen should be either the same as the key or one-stop under. i'm not familiar with Ultra 2 so i can't answer that.
 
Funny that Ultra 2 came up cause I just happened to demo it due to my frustration with FCP. I have to say it is a really impressive program. I was able to do a pretty good key, way better than what I had going on in fcp, and I did it literally twice as fast. Go to www.seriousmagic.com and download the trial you'll be glad you did. I think this is gonna be the way to go for me. Too bad I have to fork out more dough just to get a decent key, maybe I'm throwing in the towel too soon on fcp...time is money though.
 
dlang said:
I think this is gonna be the way to go for me. Too bad I have to fork out more dough just to get a decent key, maybe I'm throwing in the towel too soon on fcp...time is money though.
Click to expand...

From discussions on the topic of chroma-keying and 'inexpensive cameras', industry friends have indicated the most significant problme is with the fact that the colors are not represented identically. Blue is the least best represented, not only is it spacially 'compressed', ie given less resolution, but also in intensity quantization, ie there is less sensitivity to blue values.

So the recommendation was to go with 'green', rather than some other color, because green gets treated 'best' of the colors.

If on the other hand you find a software tool that does 'good enough', then clearly that's better than having to buy a more expensive camera...

Later on this summer I have a project which will need some chroma-keying technique so I'll be verifying this 'industry wisdom', using the DVX100A.

As a note, a chroma-key example that I have on my AfterEffects install disk, has green chroma halos and requires a certain amount of dedious parameter tweeking to minimize the unwanted effect. It still doesn't elminate it completely, and the cutout figures have a 'cut out' look. So, I'm going to have to really take care on the lighting and matching what is chroma-keyed in to really minimize this problem...

On a lighter note, on one of the Star Wars movies... I think it was number two of the old series, when they 'updated' the video release sometime in the mid-90's some of the processing was to eliminate 'bleed' problems that were not done in the theatrical and early video releases... One example where the processing was re-done, or fixed up, was in shots from the 'in the cockpit point of view' out to the snow fields. The early version one can see a small band or gap between the window and field of snow, and the frame of the window.
 
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