You may not want to spend days and tens of thousands of dollars to achieve a realistic key for your projects. Your entire project's budget may be less than one shot of a major blockbuster film. Yet you still want the final product to be realistic and believable without selling your car or house, or spending weeks to achieve that goal.
If there is one word for shooting green screens properly it would be: TESTING. The brand of camera and lens is important to the final result. But a poorly lit green screen shot with a great camera and expensive backdrop can be far more tedious and difficult to key than well-lit footage shot with more modest equipment. Testing your set-up can save hours or weeks of frustration. If possible, plan to shoot some tests BEFORE your actual shoot, and make adjustments where needed. Whether you are shooting with Red EPIC, HDSLR, P2, or other format, proper lighting is crucial to obtaining a good key quickly.
Please think of it this way: you must light two distinct areas, 1. the green screen, and 2. the foreground elements. The foreground may be an actress, dog, car, etc., whatever you want to key.
The key (pun intended) to lighting the green screen itself is to light it as evenly as possible. If you use cloth, make sure it's GREEN (not blue-ish or yellowish), and make sure that there are as few wrinkles visible as possible.
Look through the camera at your monitor. If there are 'hotspots', move lights around, remove or bounce lights, etc., to get the smoothest and most even green possible. Frame your first shot as wide as possible, and shoot some footage.
Load your image into After Effects, or save a still frame as a jpeg at high quality (100%), and import it into Photoshop, GIMP, etc.. We will be talking about RGB levels in 8-bit, where 0 = black and 255 = white.
Take your Color Picker and move it over the image. Inspect your values in the brightest and darkest areas of the image. You want the G (green) values to be ideally around 155, and R (red) and B (blue) ideally around 10. In reality, 135-175 for G (green), and R (red) and B (blue) values around 20-50 is acceptable. Do not overexpose the green screen (255), and try to make the values as consistent through the image as possible.
We have been sent "green screen" footage from people asking how to improve their footage. The footage was actually an over-exposed blueish-green screen. The G (green) values were clipping (255) and their B (blue) values were over 200 in bright areas ! That's more than bright enough to be considered a blue screen.
Next, light the foreground elements however you want. In past years, it was recommended to rim-light foreground elements with magenta filters to neutralize green spill on actors from the backdrop. That is no longer necessary with the Despill filter found in PHYX Keyer.
Check out the images below:
On the big day, plan to shoot a 'Clean Plate', which is simply the greenscreen background without the foreground elements. This short take can further help to smooth your shot with the ScreenCorrector plugin in PHYX Keyer. Check out the images below:
In the next image, we compare the mattes:
Other points to consider: We recommend using the highest quality camera, lenses and recording settings possible for shooting green screens.
PHYX Keyer supports After Effects, Premiere Pro, Motion, and Final Cut Pro (X). For more information about PHYX Keyer, click HERE.