Chroma is an important technique in our virtual world. Let us discuss what is CHROMA before discussing about “Lighting in Chroma”. Chroma also known as keying, is a process of creating transparency in a single image or in any sequence of images by a single colour value or by brightness or lightness value. In this process a certain range of pixel is hidden to make the area transparent so that any background which is placed beneath is visible. Chroma can be done on single image as well as sequence of images. There are many types of Chroma according to requirement.
Earlier for shooting any movie or footage, huge sets were made according to the requirement of the movie. Nowadays maximum characters are shot in front of a blue or green background, also known as Chroma screen. Hence the Chroma is just a colour information which is pure and there should not be any variation in it. This single colour background is made transparent with the help of some options in compositing software.
There are some reasons to choose green or blue colour for Chroma background-
- Green and blue colours are not present in the human skin.
- Less light is needed to illuminate green Chroma
- Blue is used when the foreground objects consists of green colour.
- Blue and Green colour channel consists of less noise.
- In digital cameras are most sensitive to green colour.
Let us discuss about the importance of lighting in Chroma. Lighting is the most important phase of any type of shooting, whether it’s a still camera shoot, live shoot or a Chroma shoot.
When shooting in front of a Chroma screen following measures should be taken:
- Separate lights should be used to light up the foreground character and background screen.
- Chroma should be lit up evenly.
- There should not be variation of light in Chroma. It should look over exposed when it is seen through camera.
- The character can be lit up according to the requirement of the scene but the lighting done on the character should not affect the Chroma light.
- The edges of the character should have a back light effect, to avoid this effect due to blending of edges with the Chroma screen.