Grainy/Filmy Green Screen Results?

KRyan wrote on 12/7/2009, 3:57 PM

I'm new to video and have been working on doing chroma-key with a green-screen background for music videos. I'm getting pretty bad quality and am wondering what I'm doing wrong.

This video: http://kentheriot.com/videos.htm is a clip of one I'm working now. I have 2 vid tracks, one a bunch of stock footage that gets used as the background, and the other is me in front of a green screen.

Issue #1: I can't seem to get myself to look clear after I've applied The Chroma-key FX (saturate greens, follwed by Choma-Keyer with channels fine-tuned.

Issue #2: The background always looks really grainy when the foreground video is superimposed over it.

I used a mini DV Camcorder (Canon ZR-85) for the video. I shot against a green sheet in my bedroom studio. The sheet was designed for "green-screen" use, but I don't have much in the way of "video lights" for it. I just used natural light from the windows.

Does anyone have any tips how I might make the quality better?

Thanks!

Ken

Comments

farss wrote on 12/7/2009, 4:54 PM

"I just used natural light from the windows"

That's where your problems began. Invest in some proper lighting for your screen. You do not have to spend much money. Even some four foot fluro fitting that you can find on cleanup days or junk piles will do. Get some "cool white" tubes for them. Lash the lights to some stands, old pedestal fans are a source of usable stands. You need TWO, one from each side of the screen.

Now you need some lights for the talent. Again you can find fittings from the same sources as above. Reading lights, the ones with tall stands are the best, just fit them with "cool white" compact fluro lights. If you have some cash Cinefoil (black heavy aluminium foil) can be used as barn doors etc to control spill. As none of these lights get hot you can use gaffe tape, plastic pegs, anything to hold things in place. Just take care of the electrical hazards. These lights done use much power so you can get enough watts out of any domestic socket to run everything.

Bob.

KRyan wrote on 12/8/2009, 6:49 AM

Thanks Bob! Great info. I've got a lot to learn.

Ken

JohnnyRoy wrote on 12/8/2009, 8:34 AM

> I've got a lot to learn.

You might find Keith Kolbo's excellent article Tight Budget Lighting for Chroma Key a good starting point. Keith gives very practical advice that won't break the bank.

~jr

LReavis wrote on 12/8/2009, 12:51 PM

the "tight budget" approach is good, and I used to light that way. However, in my new cramped space, I decided to try smaller green-screen lights. I now use 4 45-watt CFLs with a color temp of 5500 degrees available on ebay (http://cgi.ebay.com/4-Daylight-CFL-Photo-Video-Light-Bulbs-45W-150W_W0QQitemZ390127837282QQcmdZViewItemQQptZLH_DefaultDomain_0?hash=item5ad56e6062). I've read that that's the color for most "daylight" presets on prosumer cams, and it allows use of keys and floods of the same color, so that any spill won't much affect the green color of the green screen.

I position the 4 about 3.5' from each of the corners of a screen that is about 7' x 7' - and waveform monitor shows pretty even illumination. I once made a small square crop in Vegas and moved it all over the screen while watching the waveform monitor. There was some variation, but not bad.

I ironed the green screen with a steam iron while hanging in order to get rid of most wrinkles.

The talent stands about 6' in front of the screen and gets a key light consisting of 4 27w 5500 degree CFLs in a row in a horizontal fixture about 3' wide, hanging above and slightly to one side of talent at a distance of about 3'. I've found that an eye light isn't needed with this arrangement, and no fill is needed. Black kraft paper supported on wires provides barn doors to keep their spill onto the green screen to a minimum.

Usually I put a 27w 2500 degree spot just below the talent's head to the rear, very close. It gives a nice bright yellow outline of hair and some light on shoulders. It also gives a bit of reddish tone to some of the planes on cheekbones, etc. Placing it a shoulder level, with the cameras a little lower, allows talent to move a bit without the light coming into the camera's view.

The talent light is a bit strong for the green screen light - giving a green screen level that is perhaps 55% of the brightest level on the talent (not counting the really bright tips of hair, which get clipped on the whites). I've read that a 70% level for the green is ideal; but I'm getting pretty good keys.

For keying software, I start with the free AAV colorlab software and use it to one-click white-correct both cameras. I also use it to saturate the green to 100%.

I follow that with Pixelan's BlurPro, choosing a gaussian blur of about 40 with a "preserve edges" style set to 86. This gives a nice smooth green and gets rid of some talent wrinkles too, while preserving edges.

If Pixelan is an expense you'd rather avoid, I get about the same result with the free Mike Crash Smart Smoother.

I pull the key with NewBlue's chromakey, mainly because of it's remarkable spill suppression. I purchased some red gels, but never could get rid of all the green in the talent's frizzy hair even with a lot of red light shining on the hair. I paid about $80 for NewBlue's Essentials II, and it has been worth every penny. You may have to pay more, as I bought it when Vegas 9 arrived as a special offering from New Blue.

While in New Blue, I usually set Sensitivity to 0, color range to about 40, Spill Suppression to 100, Soften to 2, and sometimes with a tiny bit of Shrink. I find that the Soften eliminates the need for chroma blur preceding the keyer in most cases; otherwise, animated edge artifacts may appear when playing the video wherever there is motion in the images.

Last in the effects chain is a Sony Unsharp Mask, or else Sony Brightness and Contrast. Setting the Unsharp Mask at any level above zero often gives a good bit of contrast enhancement. If not, then I beef up the contrast just a bit with the Brightness and Contrast, for the final destination of my stuff is web delivery - requiring a bit more punch than, say, DVD delivery.

I'm really liking shooting talent against a green screen now that I've got the hang of it. Rendering is slow (about an hour for a minute of video on my Q6600 @ 2.7 gHz), but it gives a lot of artistic freedom - not only the ability to change backgrounds at will, but also where to place the talent on screen. Simply leaving the background black or deep blue yields some interesting options, and low-bitrate of solid backgrounds works will on the web where bandwidth usually is an issue.