advanced chromakeying

DAZMAN · Post by **DAZMAN** » Sun Jul 03, 2005 8:47 pm

I know alot about the basics of chromakeying and can normally get a good key. but for a project i am doing i need to get an exeptional key. i am talking no green lines, and bleeding the outer edge with the backrop. it needs to look seemless. Using after effects. any tutorials?

Carnage7p · Post by **Carnage7p** » Tue Jul 05, 2005 2:28 am

well it sounds like what you described is a pretty good key, so if you were getting some green lines or spill before then you didn't have a pretty good key. however, it is not about the editing software that you have. it is about how you light it. now the solution does not lie in lighting the cr** out of it. that will make it bright but uneven. you need something to diffuse the light of the screen. a chimera can work wonders and you can even make your own rather than buying one. i just finished working on a film with a $500,000 but we didn't have any chimera's so we made them out of showcard (which in your case to save money you would just need a white posterboard) wrapped around the light like a megaphone. then we covered the front of the light with some opal. now you probably don't have opal either and its about $180 a roll. so you can use some very thin fabrics like silk etc. you can use different fabrics for different levels of diffusion. create a few of these to light the screen and you will have an excellent key. the lighting on your talent should be completely separate.

Raptor · Post by **Raptor** » Tue Jul 05, 2005 8:05 pm

The software capabilities do have some effect on the finished key, otherwise, why would TV stations spend the money on the systems they do to bring us the weather guy in front of the map

As far as tutorials, this one has produced the best reaults I've found in AE, or if the project has it in the budget check out Serious Magic's Ultra2
http://www.creativecow.net/cgi-bin/page ... index.html

windog · Post by **windog** » Sun Jul 31, 2005 2:31 pm

ultra is not as good as A Effects.

Raptor · Post by **Raptor** » Wed Aug 03, 2005 7:24 am

Minute for minute in time invested Ultra gives a better key than AE. With either the more time you can invest, the better the key you can produce. But I find Ultras selection, color correction and edge management tools to be much more precise and user friendly than AE. Particularly when you need to produce a quality key in a limited time frame. Here is an example of the quality of Ultra's keying. Ultra also seems to handle poor source footage better than AE. There have been a couple of shots that we should have reshot, but based on time constraints were unable to and still be able to meet our deadlines.
http://www.theundergroundtv.com/streami ... itle=Skell
Juast to give you an idea, the videos and interview were shot Saturday night January22, we left the venue about 3 AM Sunday morning. The host standup green screen was shot Monday night Jan 24th, and the green screen commercial for choking faith was shot January 25th ( and I really hate that commercial, but that was the concept they wanted!) The videos were 6 camera with an 8 track audio mix. All the mixing, synching, editing, graphics creation, and keying were done by Friday the 28th at 3 PM when we handed the master tape off to FOX for content review before airing on Sat January 29th. ( Gee, I wonder why they want to review it for content, I mean we never curse or anything LOL ) There is no way I could have gotten keys of that qaulity in the time I had with AE. The choking faith commercial was the worst with all that hair flying around LOL.... Anything with teh pipes background, and the choking faith commercial were the keyed scenes.
This one was some retty rough source footage, and would have been really tough to get even this quality of a key in AE...
http://www.theundergroundtv.com/streami ... itle=Flord

windog · Post by **windog** » Wed Aug 03, 2005 7:28 am

ah, i see. what are the render times like in ultra? I have not used it in years!

Raptor · Post by **Raptor** » Wed Aug 03, 2005 7:48 am

Render times are about comaparable to AE, the more color correction and edge manipulation you do, the longer it takes, I was seeing about 2 to 1 if it didn;t need a lot of color correction, but up to 5:1 on some of the stuff we really had to work over. The absolute worst went to about 12:1 LOL... in other words 2-5 minutes render for each minute of video. We always keyed a lot more than we used tho, any outtakes were keyed, and usually a couple takes of each segment.

padawanNick · Post by **padawanNick** » Wed Aug 03, 2005 9:41 pm

A lot of the improvements you can make are in the setup of your shoot.
What is your shooting environment like?
Do you have the ability bring a computer with capture functionality onset?

Raptor · Post by **Raptor** » Thu Aug 04, 2005 3:39 am

padawanNick wrote:A lot of the improvements you can make are in the setup of your shoot.
What is your shooting environment like?
Do you have the ability bring a computer with capture functionality onset?

Hey Nick, where you been hiding down east? You bring up an interesting point on teh direct to disk capture. I've been toying witht he idea of trying DVRack to get a good setup for green screen shooting, have you ever tried it for that, or for that matter ever tried it for any kind of calibration?

padawanNick · Post by **padawanNick** » Thu Aug 04, 2005 4:12 am

Hey man! Great to see you're still here.
Well, you know that seminar we went to in Pittsburgh ..... well ..... it's lead to a LOT of things for me.
I've been swamped busy all this year working on all sorts of FX heavy productions. .... Hollywood stuff (not feature films yet, but I'm aiming there).
Most of it I can't really share until it gets released, but I'll post as info goes public.

As for the greenscreens.....
Absolutely.
At PixelCorps, we're mainly using FCP as a DV rack setup .... even when shooting with a CineAlta, to get the waveform monitor.
A color parade monitor would be good too, but I don't see that on dvRack.

The waveform can be used to check for even lighting. See if it can be configured to show just green channel, or perhaps different color lines for each color channel. You want the green line to be up high, like over 200, and flat. If it curves at all, that means you have bright spots.

When optimizing, you should strive to have red & blue values be low on the greenscreen. At least a difference of 60, but more if possible. The scopes for measuring all this stuff are as valuable (or even more so for greenscreen work) than the ability to record to disc.

I did a whole video tutorial on how greenscreens work and some ideas on optimizing them for one of Sky's Inside Report shows last year. Not sure if it's still online though.

Raptor · Post by **Raptor** » Fri Aug 05, 2005 3:28 am

Pretty much what I was figuring could be done with DVRack, just wasn't sure how accurate it really was, price wise compared to a hardware solution with equivalent options LOL.... Glad things are going well! We did get the show up and on air, the first season is under our belts, second season in prepro now. We found a lot of things that worked, and a lot more that didn't LOL, so hopefully the second season will continue with the technical impovement we saw toward the end of season one, and the content improvement we now have the time to shoot for

. You can check out the first season episode s in wmv stream at http://www.theundergroundtv.com/streami ... player.php