Lighting the Green Screen and Subjects

Lighting is probably the most important part of proper blue/green screen production. If either the screen background or the subject isn't properly lit, then the composite will be a disaster. Following a few simple guidelines will save you hours of frustration in compositing or possibly prevent you from scrapping your footage and starting all over. Even as forgiving as several keying plug-ins can be, you want to eliminate as many potential % problems before you shoot to get the optimum results and save time in compositing.

EN You must make sure that you evenly light your background screen. If there are

/GR hot spots or shadows or even heavy wrinkles in the cloth, they will create problems in

LU your composite. Unless you are shooting outdoors with natural light, you should always

N use separate lights to illuminate your background from those used on your subjects. On professional sound stages, banks of special fluorescent light fixtures (usually Kino Flos)

A are placed all around the edge of a large wall, providing a soft, even, true-color illumi-

IN nation of the background. In smaller sets and on location, a couple of wide halogen lights

OO can be used to light the background, with the subject well in front of the lights to avoid

~ any light spill or edge glow (Figure 8.3). A separate light is used to illuminate the sub-

^ ject, usually with an additional fill light through a soft box or a reflective umbrella to

" eliminate shadows on the subject's face. If you need additional contrast, as in the case a of a subject with flowing blonde hair, you can use a small back light aimed at the sub ject's head to provide a soft glow and create more contrast from the background.

If you're working with a cyc wall or have a long length of fabric for shooting full-length subjects, you'll need additional lights to light the back wall and floor behind the subjects (Figure 8.4). The best way to do this is to use a bank of fluorescent fixtures along the top edge of the cyc wall and two side lights shining against the wall. This will light the background evenly and "hide" the transition of the wall to the floor. The subject's shadows on the floor should come only from their light source and not have multiple shadows from back light spill.

Note: You can learn more about professional lighting methods and lighting blue/green screens by visiting the Kino Flo website at http://kinoflo.com. Make sure to visit the FAQ list and the product catalog.

Figure 8.3 Positioning your studio lights correctly will provide the cleanest background key.

Figure 8.4 When using a cyc wall, light the floor for a seamless background.

Figure 8.4 When using a cyc wall, light the floor for a seamless background.

To better demonstrate this kind of simple studio setup, I created a virtual environment in After Effects, using 3-D layers and a mock green screen stage. I placed one subject, the guy in the straitjacket, back in the green screen light (Figure 8.5). Notice how the green spill and oversaturation is washing him out. This is what happens when your subjects are too close to the background screen.

Figure 8.5

Positioning subjects too close to the background screen and in the path of the screen lights will wash them out and cause green light spill.

The other subjects are positioned well in front of the screen lights—at least 10 to 15 feet from the screen. They have their own lighting source that correctly illuminates them for the composite scene (Figure 8.6). Notice their shadows on the ground in natural positions that softly fade back.

I rendered the scene (without the background character) with a composited background environment and put it together in another 3-D composition in After Effects (Figure 8.7). You can also view the virtual stage and the composited movies in the Chapter 8 folder on the DVD.

Figure 8.6 m m

The correct positioning of the subjects is O

far enough away from the screen so there z is control of their lighting exposure with- u out spill or hot spots. E

Figure 8.7

The composited scene with the foreground subjects and a background environment.

Figure 8.7

The composited scene with the foreground subjects and a background environment.

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