I have a greenscreen question

[wildstorm]

Hello, I'm new to the baords so I'm still finding my way around. I am in the process of setting up a greenscreen in my garage. I have a 10ft wide by 8 ft tall wall dedicated for this. Now reading through some of these articles on the forums, I have the option of either using a cloth or painting the wall green. The wall itself is OSB board. (I think thats what you call it) You know the stuff they use when constructing a house. Would it be ok to paint on that? I tried some cans of spray paint earlier. I sprayed 3 coats of primer and after that I applied green paint over the primered area but it seems the paint soaks into the wood. Maybe its because I'm using spray paint instead of getting a gallon of paint and brushing or rolling it on. Anyone got any suggestions? Thank you in advance.

[redkorn]

paintwould be awsome cause im pretty sure it would reflect the light more then a cloth screen. I myself used a cloth green screen so i could move it or take it down, it take about 10, 500watt lights to get it lit up decent.
http://snyder.cjb.cc/greenscreen.jpg

[wildstorm]

Right now, I have a green cloth on the wall. I'm currently doing some experiments in getting the greenscreen lit evenly. Is it better to use a digital video camera or an analog one when doing stuff like this?

[Kentertainment]

It probably would have to depend on the kind, most 1-2 ccd digital camcorders tend to wash out colors a bit more than 3ccd's. What editing program do you use, If Vegas, I'd just stick with the sheet. You can easily use and eyedrop tool to take out the color you want...I don't know about Premiere.

[redkorn]

o premier is easy to do green screen, what i use is the color key option and select the color in the bg with the eye dropper and take out as much as you can of the green without losing what you want to stay in. If there is any green left then use the 16point garbage matte to take what left out. I am using adobe 1.5 pro lower version may not have these options. But adobe does a great job with green screening!

[wildstorm]

I use After Effects to do the keying. The camera I use is a JVC vhs-c video camera. I have one shop light that is hanging above the green cloth and its postioned about 4 ft in front of it. Its lighting the cloth evenly but I'm not getting good keying from it. Here is a picture of the my greenscreen set up: http://wsfilms.net/green.jpg There's a little wrinkling but its not bad at all. I think part of my problem was that I was standing to close infront of the screen. It didn't cast a shadow or anything but I was under the light also, so when I started keying out the green, part of my skin would get keyed out also. And what is the 16 point garbage matte?

[maj_barnes]

I'm making a blue screen. I'm just using a blue tarp, a big blanket is like $10.

[wildstorm]

Doesn't the tarp reflect the light?

[Raptor]

Believe it or not, the analog vieo will probably key better, getting it into the PC without dropping frames at full size is a bit tougher, but you avoid the DV jaggies. That being said, Using a good DV cam can produce great results. Personally I use Serious Magic's Ultra for all our keying. The control is a lot simpler than the methods with AE to produce similar results, and I like the color correction in Ultra better. Here is an excellent article on creating a matte for AE, and it works well, a bit more time consuming that Ultra, but a hell of a lot cheaper if you already own AE
http://www.creativecow.net/show.php?pag ... index.html
Your keying problems are probably two fold. A single lamp will never be able to evenly light the screen. It may look that way to your eye, but to tet it, turn zebras on on the cam and then adjust the exposure and watch how the zebras move across the screen, when the entire area comes up to zebras at the same exposure, THEN you have even lighting. Also, separation of your talent from teh screen will eliminate some of the color bleed you get, minimum of 6 - 8 feet. And teh talent should be lit by a separate set of lights, preferable diffused or bounced to reduce any shadows on teh screen. The best thing to do is play with your lighting till you get it right, lots of tet footage, record your light setup for each test, then pick teh best couple and try to tweak them. We normally shoot with 3 200W scoops lighting the screen, Two bounced rom white ceiling, one bounced from floor using white foam core. Talent is light by 2 x 150W scoops bounced, with 2 40 watt pin lights for hair lights, or fill lights as the scene dictates.
If you watych the episodes of The Underground at http://www.theundergroundtv.com/streami ... player.php you can pretty much asign a chronological order to the episodes that feature chroma scrrens as the season progessed and we refined our lighting setup.

[ct_bullet]

i've done blue and green screening before but nothing of that scale, what are you planing on using it for?

[jcdenton]

Hi. In fact your question about analog and digital cameras is a very important question! If you have a good analog camera, use that one for greenscreening! This is the reason why: MiniDV Cameras will store their movies in the formats 4:2:0 (PAL) or 4:1:1(NTSC). This means, for a block of 4 pixels the format stores only ONE color tone. the undefined 3 pixels will then use an interpolated (mixed) tone, using its defined neighbour color tones. This may look ok for the human eye, but as soon as you try to chrome-key a fine contour, you'll end with ugly, blocky artefacts, forcing you to blur the outline, but even then there will be massive artifacts, especially when the contour is in motion (burring will then produce a flickering contour).
So use the analog camera, if it's SuperVHS or Hi8 (ordinary VHS is not good enough, of course). If your want to do greenscreening with Digital media, you should buy a DigiBeta Cam, but that's an other price range.

An other solution would be to film things in a big, closeup format and then downscale it in the editor. if your downscale it to 50%, you will virtually get 4:2:2 color information (means every pixel has its true color tone) and thus result in much smoother contours.

A further advice is. make sure your greenscreen is as far from the actor away as possible, this will make it easier to light it evenly and prevent green refelctions on the actor (global illumination).

[UFProductions]

Well, tossing my two cents in here on greenscreens; I've found that nothing surpasses green poster paper in cheap, effective screen material. It's cheap, completly matte, smooth, and easy as hell to set up and take down, you just need tape. The only important thing is to ge the right kind (electric neon green poster paper, it's a perfect match to chroma-green, and it uniform in colour, not the cheap construction paper stuff you get handed out in kindergarten), and to make sure your seams overlap nicely, with no shaddowns. (Double sided tape works well for this.) Best of luck whichever route you chose!

[rep22]

I use the exact same routine as UFProductions. Bright greet poster board works well. I bought about 16 of em when they were on sale 4/$1 at a hobby store. Best deal I've gotten on movie stuff. Its something to consider...

[wildstorm]

I have the back wall painted in green. Now its just a matter of getting it lit evenly. I also bought me a new camera. Its a Sony Hi8 CCD-TRV138. During my preliminary tests, I was able to key out the majority of the greenscreen. The problems I ran into was that it wasn't evenly lit and I was positioned 6ft away from the wall when I should have been at least 12ft away. So I was actually keying part of myself out. I'm not doing full body shots because my garage isn't big enough. I found that using this new video camera was better than using the older VHS-C camcorder that I previously had.

jcdenton said:

An other solution would be to film things in a big, closeup format and then downscale it in the editor. if your downscale it to 50%, you will virtually get 4:2:2 color information (means every pixel has its true color tone) and thus result in much smoother contours.

I use DVD Xpress to capture my video into the computer and I do the keying stuff in Adobe After Effects. When I capture video, the screen resolution is at 720x480. If I shrink that down to say, 320x240 I should get smoother contours around myself when I key out the green? Because I noticed that the edges are kind of pixelated and then I end up feathering the edges to make them smoother.

[jcdenton]

Yes, scaling down will give you a better matte line. Of course, you cannot scale everything down. Especially not when your garage is small. Scaling may also mess up interlacing. Deinterlacing will blur the picture, but since you scale it down, this doesn't matter that much.

The best solution that I know would be to buy the cheapest HDV camera, preferably a 1440 one and then scale that down to full NTSC or PAL. There is one HDV by sony, pretty cheap since it uses a one-chip CMOS solution. Unfortunately it can do only 1080, seen for 1770$. It has some silly features like a touch screen menu (horrible), but basicly it would be the cheapest solution for something "near-4:2:2" that is required for proper chroma keying (like TV stations do with their news speakers).
Of course, you still can use your analog hi8 camera. You only need to make sure your digitizing app will save it on your computer using a codec that saves in 4:2:2. If you don't care about that, it could be saved in 4:1:1 by accident (it's even likely since it's standard) and you would get pixelish outlines again.
Im not sure right now what codec could be used, you may ask in some video maniac forum (eg. die doom9.org community). I think when you use a codec that i saving in RGB (instead of the common HSB aka YUV2), the problem will be solved. I guess the Huffyuv codec can save RGB, but since it's lossless it eats a lot of diskspace.

[Bodysnatcher]

I have placed this post elsewhere but this seems to be the right place so sorry if you have double read this, but how do I scale my actors in green screen? If I wanted a shot of my actors walking up a gangplank, the only way I can think of would be to have a green screen of epic proportions and sett the camera back far enought to make them small? this seems silly so is there a way of filming them at a more appropriate distance and then scaling them down to match my back ground??

[jackbauer24]

you dont even have to use green. Just have them walk in front of a white wall or something and just color key it out. White walls are easy to find, and if you dont have one at your house, there is probably one at your school or something