Place your subject at least 9 feet (3 meters) in front of your blue or green screen.
Your camera must be as far away as possible. This will result in a narrow lens angle.
Important: green or blue screen is out of focus, irregularities will be less visible; a smaller portion of the green or blue screen is visible, which is far easier to light evenly; your foreground subject doesn’t cast shadows on your background.
When you do blue screen, you might want to use an orange/yellow toned backlight. Not too colored, half CTO or Straw will do. This will reduce possible blue fringing in hair or clothes, because the color of this backlight is complementary to the blue. The result after you have keyed will look like a normal white backlight.
If you use green screen you can use a pale pink or magenta correction filter (1/4 or 1/2 minus green).
A simple chromakey recipe:
- Set up a blue or green background of the type you are going to use in the shoot.
- Light it evenly
- Put your camera on manual iris
- Place a white card directly on your background (you can also write the f-stop that you use on this card for reference). Make a series of recordings, about 10 sec each, at different f-stops, starting at the underexposed side. So f11, f8, f5.6, f4, f2.8, f2.
- Capture the footage and put it in the timeline
- Apply a color correction filter to the clip
- In the effects palette click setup
- Turn on the scopes and choose vectorscope and Y (luminance)
- Locate that part of the clip where the white card just reaches 100% on the waveform monitor. It might be just below 100% at a certain f-stop and clipped to 100% in the next one. In that case it will be somewhere in between.
This basic steps will give you very nice kyes
