OT: New to greenscreen

UlfLaursen wrote on 6/8/2010, 11:17 AM

I am going to do my first music video very soon, and I am trying to find out how to shoot it.
One of the ideas is to shoot some green screen footage of the singer, and put her in front of some different clips.
My questions now: is it possible to make some decent green screen footage on a tight budget, and how would you do it? Green clothes? big board? inside / outside in the sun?
As far as I know you need very even light on the whole green board/clothes and of course no shadows from the singer to make the keying as good as possible, but besides that I'm a bid lost.
Has anybody tried this and have some advice? Thanks...



K-Decisive wrote on 6/8/2010, 2:06 PM
Some basics but keep goggling: Lots of articles out there.

The screen needs to be really really even ( no folds, light as even as possible) I have boards painted with Roscho chroma green. Getting a real green screen is much better because there is a much sharper color spike in the spectrum.

keep the actors at least 5-6 feet away ( the farther the better) and make sure they don't cast any shadows on the screen. The subjects and screen will probably need separate lighting sources, unless you are doing it outside.

Use a faster shutter speed on the camera ( 1/100, 1/250) , this will limit the edge blur somewhat.

You can try back lighting the actors with amber lighting to counteract green splash.
The lighting needs to match what ever you are putting in the background.

If you do all of this correctly, Vegas can pull a decent key, but key light in after effects works better. Adding a secondary color correction process after the keying can help with edge spill, you can also use a secondary color correction process before the key to even out the green.

Anyone else? Another sticky candidate if you ask me.
Dave_OnSet wrote on 6/8/2010, 8:21 PM
Just a couple of added suggestions --
If you don't need to go 'head to toe' then move your subject further in front of the screen (minimum 10') and put some green gel on the lights you are using to light the green background. I know it sounds stupid, but of there is any sheen or reflectivity to your backdrop, this will help.
Also, try a light magenta on your edges and back lights. (magenta is the oppossit of green). Amber works better for edging with Blue screen.
If you are shooting full body (including the feet) consider using a pola filter to minimize floor sheen from the backlights.
Also remember that reflective objects are your enemies - particularly things close to the green - like shiny shoes!
Try to run a test and check the key while you are shooting!
And beware of faded blue jeans - they often have a lot of green in their faded areas.
Color depth is your friend, so I've started recording all my green screen stuff with a NanoFlash at 100Mbps (when shooting with my EX1)
I still have an old copy of Ultra on an ancient laptop that I sometimes use to check the key, or to give clients an idea how a shot will work.
Good luck with it!
UlfLaursen wrote on 6/8/2010, 9:00 PM
Thanks, Guys for the good info :-)

Spot|DSE wrote on 6/8/2010, 9:29 PM
lite well. Lite weight.
Be sure you know the direction of the sun/key on the background subject so you can match it in post. Avoid busy clothing. Avoid flyaway hair......
Light the singer as though the key doesn't exist. Then work the key in to place.
No more than 4-5 liighs shoudlbe needed. Bounce a lot.
typing ins a bus is creazy.
UlfLaursen wrote on 6/9/2010, 4:00 AM
Thanks Spot :-)

jeff-beardall wrote on 6/9/2010, 6:37 AM
+1 for keylight. It rocks. I use lurid green spandex cloth from the fabric store for my bg. Pretty well any saturated green will work. Rosco is good for industry style workflow but not neccessary.

LReavis wrote on 6/9/2010, 9:12 AM
in addition to the above, I suggest:

1. Get a 3 chip camera. I bought a cheap ($750) Panasonic TM-700 and I got better chromakeys than on Sony HC1s.

2. Use AAV Colorlab (free) or other color corrector to saturate green to 100% before the keyer (but check to be sure it doesn't change colors on talent; Caucasian skin tones seem unaffected in most cases). Also apply 3% chroma blur with AAV Colorlab.

3. If possible, use the free smart smoother or New Blue's smoother before the keyer; this will smooth out any tiny variations in the green screen (sometimes important if you use fabric), and it will minimize noise from the camera. A smoother with post-sharpening will make some faces look better, too, without loss of detail for hair, glasses, etc.

4. Use New Blue's chromakeyer or other plugin that can suppress spill; much easier than endless tweaking using color correctors.

5. I've experimented with magenta gels to rear or side, but didn't like the results (but I do use some side/hair/back lighting in order to get a good contrast with green screen and to enhance talent).

6. If you get talent with frizzy hair, not to worry; I get good keys with frizzy hair by following the above steps.

7. Aim for about 70% as much light on the green screen as on the talent. Use plenty of light so that gain-up inside the camera won't be needed for achieving adequate brightness (again, you want to minimize camera noise). Use the scopes in vegas - RGB Parade & Histogram are helpful in getting good lighting. In my case, I use 45-watt CFLs spaced about 4' in front of the corners of a 7' x 7' green fabric, with talent about 6' in front, lit by four 45-watt CFLs nearby overhead and slightly to right, with various side/back/hair lights - and an eye light hard by the two cameras (one tele, one wide). I might be happier with brighter lights, but brighter lights = deeper depth of field, which means the screen itself will be more in focus - just what you DON'T want when trying to cope with wrinkles, etc., in fabric.

8. Use 5500-degree Kelvin color temperature lights. Most cameras have maximum sensitivity in that color range (again, yielding minimum video noise). But I do use 3500-degree side lights sometimes to bring out a warm skin tone to the rear-side of the head.

If you do all the above, you should need only zero to 3% softening in New Blue, plus a bit of shrink. You should see almost no dark halos (or none at all), no jaggies, and very clean keyed areas. Incidentally, I seem to get better keys with deinterlaced video, but I'm not certain of that. In any case, the TM700 gives progressive, and I deinterlace HC1 HDV takes and render to Cineform before putting them on the timeline for keying. Because the blur and saturation and smoother take so long, I also render these plugins to Cineform even from my TM700. Then, when I put those Cineform clips on the TL of my final project, they don't take nearly as long to render as would be the case if I tried to do all in one fell swoop; and preview framerates are a bit better (but not great). I also save any final color/contrast correction for talent, if needed, for a plugin placed AFTER the keyer.
kkolbo wrote on 6/9/2010, 9:21 AM

Tight Budget Chroma Key Lighting
Using Chroma Key and Chroma Blur in Sony Vegas


I don't know that I would trust the guy who wrote those articles.