Green/blue/red screening, also known as Chroma Keying, is the process of removing a certain target color from the image, making it transparent.
In my years of experience, never does green screen just work like everyone claimed it did. THEY LIE. They use masks and such, which I'll explain in other tutorials.
Each color has its purpose, blue is for low motion, TV and film. Red, which most people dont realize exists, is for shooting dark objects and placing them into a night or dark scene. Red should never be used with people, because the human flesh tone contains red. Scenes from Independence Day use red screen for the spaceship scenes. Green, is for fast motion, miniDv, DV, BetacamSP, photos, and is generally much easier to work with because humans do not have green within their skin or body, therefore removeal of this color is much cleaner and easier.
Green Screen on a budget
Alright, if anyone has ever looked at professional green screen, you'll find its damn costly, even on ebay. A 6'x9' would start at 60$, and a small paint can would run you 30$. Why it costs so much is because it is in every way non reflective. If you take a peice of neon green posterboard, yea you will get quick results, and loose half of your subject, because it will reflect on his or her skin.
But, there are simpler things in life that will suffice. I explained to my girlfriend once after a failure blue screen shot on how this works, and that i needed a better fabric ( i was using a blue felt horse blanket). She knew right away this store Joanne's Fabrics would help. Low and behold, they had neon green felt, cost me 14$ for a large chunk of it. I beleive its a 6'x12' sheet, they charge 7$ by the yard.
Now in this pic, my digicam doesnt do the screen justice, its actually a healthy neon green:
Key factors in a green screen
In theory any shade of blue or green will do. Neon or flourescant is the best. Something i failed to illustrate, is the importance of REMOVING ALL WRINKLES. Wrinkles are bad, as they cause shadows, which causes a darker shade of green, which causes problems later. I'm using the family bookshelves here, and normally what I do, is use tacks and keep it pulled tightly.
Lighting
Shadows are a no no here. Any shadows can and will cause you problems. I have done many experiments, and I have found incandescant to be the WORST form of light. Those handy little clamp lights? Yea almost completely worthless.-ALMOST.
What i did find works great, is 1 flourescent light fixture directly above your subject. Now in my basement, I only get half of my screen lit up correctly:
The tripod will be my model since its late and no one else is up. Notice how the left half is nicely illuminated, yet the right is dark and spotty. Well you COULD shine a light on it, but direct lighting is terrible, since it directly places shadows. You can use those cheapo 5$ clamplights, and get the flourescant tubes that go into a regular lamp. They dont do as great as an effect, but it definently is an improvement. Make sure its placed above the subject.
The Blacklight Trick
We wanted neon green for a reason! Neon or flourescent colors glow under the use of a black light. This technique, was totally original by me, I thought of it after a night of garbage picking. What we need for this is FLOURESCENT black lights. Incandescant ones simlpy do not have the same effect.
Full 24" blacklights cost alot at your local head shop or Spencers or whatever. I've seen the entire kit go for 29.99$ at Spencors, and 15$ for the tube. Now why buy that when theres a much cheaper, more effective alternative?
Home Depot to the rescue! A blacklight tube at Home Depot or Lowe's is generally around 8$ or 9$. The fixture can be bought for anything from 3$ to 8$. I'm talking about your cheap white shop light fixture. Spencer ones wont work because of their highly reflective mirrors.
So once you get your tubes and fixture, we must paint it. Simply spray paint the inside of the fixture a gloss black. If we keep it white, we will get a blue/purple reflection, and thats just too powerful. Paint it like so:
I only have 1 tube, the other burned out. Luckily you only need 1 tube to start this fixture.
Angle the fixture so its about in the middle of your subject, but lying horizontally and close. Standing it vertically for some reason casts shadows. The end result will look like this:
Ok, when i took the picture, you couldnt see the purple reflection, obviously i did something wrong. Idealy, one would place the blacklight behind the subject so this exact thing doesnt happen.
Final Thought
My personal preference would be the flourescant bulbs in the clamp lights. Most buildings have flourescant lights in them anyway, and using an incandescant bulb just wrecks the whole composition.
