With the rise of self-media and virtual chroma-keying technology, more schools, institutions, and companies are adopting virtual studios. These studios use limited physical space to create limitless virtual scenes, allowing for dynamic scene changes. Many virtual studios now use green screens as their chroma key background. However, a common issue arises during video keying where subjects’ faces appear green-tinted. What causes this issue? Many might wonder. Based on our experience in studio lighting, here are some possible explanations:
Firstly, video keying commonly uses green and blue screens. In terms of color characteristics, green is brighter and prone to “spill,” which causes the green color to reflect onto objects and people. In contrast, blue is generally darker, so it exhibits less color spill.
Secondly, improper overall lighting setup can lead to uneven light distribution. Since green is more sensitive to light and prone to reflectance, while blue absorbs more light, reflection issues are primarily encountered with green screens.
So, how can we address the issue of green screen reflection in virtual studios?
1. Adjust Lighting Brightness: It’s crucial to reduce the background light brightness and then adjust the key light brightness according to the light ratio. A typical setting might be Background Light: Key Light = 1:1 = 1000 lux:1000 lux, Back Light: Key Light = 2:1.5 = 2000 lux:1500 lux, with a central illumination of 1500 lux-2000 lux.
2. Employ Ring Lighting Theory: Given the uniqueness of virtual studios, we use chroma key technology to process green screen keying. The host moves around a certain area in order to enhance the interactivity and authenticity of the program. So it is inappropriate to use traditional three-point lighting commonly found in news studios. To minimize green spill on the host, ring lighting should be applied. This includes background light, back light, top light, side light, and key light, ensuring overall lighting uniformity.
3. Use Black Drapes at the Ends of the Screen: To absorb excess light, hang black drapes at both ends of the green screen. If the chroma key still results in a green tint on the subject, consider laying black cloth on the floor of the green screen area as well.
