Additive color synthesis involves superimposing lights of different colors to create new ones. The three primary colors are red (R), green (G), and blue (B). Their mixture at maximum intensity produces white. This is the principle used by all screens.
Discover FizziQ
How to measure it in class
With the FizziQ app, the colorimeter allows analysis of additive synthesis.
Steps:
- Open FizziQ and select the “Colorimeter” instrument
- Analyze different colored areas of a screen with the magnifier
- Observe the R, G, B sub-pixels that make up each pixel
- Measure the R, G, B values of different colors
- Verify: R + G = yellow, R + B = magenta, G + B = cyan, R + G + B = white
Scientific activities on this topic
- Study of screen pixels: https://www.fizziq.org/en/activities/additive-color-mixing-rgb/
- Creating colors with RGB LEDs
- Comparison of additive and subtractive synthesis
Learn more
Primary mixtures:
| Mixture | Result |
|---|---|
| R + G | Yellow |
| R + B | Magenta |
| G + B | Cyan |
| R + G + B | White |
| None | Black |
Why RGB?
These three colors correspond to the maximum sensitivities of the three types of cones in our retina. By stimulating these receptors in different proportions, any perceptible color sensation can be recreated.
Digital encoding:
Each R, G, B component is encoded on 8 bits (0-255), allowing 256 x 256 x 256 = approximately 16.7 million colors.
Additive vs subtractive synthesis:
- Additive (lights): light is added, the mixture brightens
- Subtractive (pigments): light is removed, the mixture darkens
Formula
Hexadecimal encoding: #RRGGBB where RR, GG, BB are in base 16 (00 to FF)
Examples:
- Pure red: #FF0000 (R=255, G=0, B=0)
- White: #FFFFFF (R=255, G=255, B=255)
- Black: #000000 (R=0, G=0, B=0)
- Yellow: #FFFF00 (R=255, G=255, B=0)
Application examples
- LCD and OLED screens use RGB sub-pixels
- Video projectors superimpose three RGB beams
- Stage lighting creates atmospheres by mixing RGB LEDs
- The JPEG image format encodes each pixel in RGB
FAQ
Q: How can you see sub-pixels with FizziQ? A: Use a magnifying glass or loupe in front of the screen, then the FizziQ colorimeter to analyze the colors.
Q: Why does mixing all paints give brown/black and not white? A: Paint works by subtractive synthesis (it absorbs light). The primaries are then cyan, magenta, yellow, and their mixture absorbs all light.
Q: Is screen white really white? A: It is perceived white. By analyzing with FizziQ, you see it is a mixture of R+G+B, not all wavelengths like sunlight.
Q: Why don’t screens have yellow pixels? A: Yellow is created by R+G. Three primaries are sufficient to recreate all perceptible colors. Adding other primaries would not add new colors.
Related concepts
Visible spectrum - Primary colors - Subtractive synthesis - Colorimeter - Color perception - Pixel