One of the biggest technological benefits to lighting designers is the ability to create a multitude of different colors from a single lighting fixture. Most automated lighting fixtures allow for color mixing capable of creating millions of different hues. This is achieved via two different methods known as Additive or Subtractive color mixing.
Subtractive color mixing uses white light source with a series of filters to eliminate certain wavelengths of light. Typically, these systems are known as CMY (Cyan, Magenta, Yellow) color mixing and consist of dichroic filters. Each of the three filters removes colors from the white source to reveal only the Cyan, Magenta or Yellow wavelengths. Because the filters are not solid, but instead incremental in terms of saturation, they can be combined to create a multitude of different hues. For instance, combining magenta and yellow produces a red color. Similarly, a half saturation of magenta combined with a full saturation of cyan creates a beautiful sky blue color. If all three filters are combined with full saturation at the same time, the output is nearly black.
On the other hand, Additive color mixing uses multiple sources of colored light that combine together to create a white output. Most of these systems are based on RGB (Red, Green, Blue) and are very typical with LED products. Each LED emitter outputs a specific range of wavelengths (color), and since the intensity of each can be adjusted, so too can the amount of saturation. By combining different color LEDs, one can create many different colors. For example, to create a magenta output the red and blue emitters must be combined. To create a deep blue output, only the blue emitter must be used. Because colored LEDs are very limited in terms of the wavelengths of color they output, many fixtures also include a white LED to ensure a perfect white output. This is often referred to as an RGBW system. The white LED can also be combined with colors to create pastels, such as pink (red and white) or lime (green and white). Some more complex additive color mix systems also use additional colors such as lime, amber and various shades of blue or green to allow for a greater spectrum of color. This also aids when combining all sources to produce a true white output.
There are, of course, pros and cons to each of the color mixing systems. CMY systems use filters and mechanical devices, where RGB systems typically involve electronics and LEDs. More importantly, saturated colors tend to output less lumens with a subtractive CMY system, as it filters out more wavelengths. Alternately, with an additive RGB system, you are using the full output of emitters to produce the saturated color. For this reason, a deep blue or red is brighter with an additive system than a subtractive system.
Lighting designers must choose carefully when considering lighting fixtures. The type of color mixing selected has a direct result on the output onstage and the programming within their console. Martin Professional lighting fixtures, such as the MAC Viper Profile and MAC Quantum Profile, utilize subtractive color mixing, while LED-based products such as the MAC Aura XB and MAC Quantum Wash are based on RGBW additive color mixing.
Do certain types of color mixing fit better in particular applications? Let us know your thoughts in the comments.