White Light – What is It?
Ask someone what is white light and they’re challenged to provide an answer. No reason to feel alone for there is No clear definition. Organizations including IES, IALD, CIE, IEEE, ANSI and NEMA have not agreed upon a standard with no near term agreement in sight. This lack of consensus creates problems for engineers, architects, designer and consumers who benefit from a clear definition that supports uniformity.
White Light – Standards?
Current standards for defining white light are subjective and vary based upon the light source and even culture. We see color as reflected light where variations result from noticeable distortions. The distortions are the result of the human eye perception of a single color that is actually a vast array of light wavelengths and hues.
Although there is no one specific number in degrees Kelvin that corresponds to white light there is a general consensus in respect to a temperature range. A general rule is white light ranges from 3500K to 4100K which is the center point for commercial applications. LED lighting is capable of being fine-tuned allowing the tightening of this Correlated Color Temperature (CCT) range.
Hue, Value and Saturation are used to describe color. Hue refers to the pure spectrum colors i.e. red, blue, green, etc. Value is the relative lightness or darkness of a color. Darker values are shades and lighter values are tints. Adding black to create a darker shade or white to tint a base color modifies its color value. Saturation refers to color depth or purity. The HSV scale is derived by combining hue, value and saturation values. Lighting conditions shift hue, alter value, and distort saturation.
As LED lighting continues to advance the range of applications are endless. Light can be controlled to match up with circadian rhythms modifying behavioral changes such as feeling sleepy or mood altering perceptions. White light alterations enhance visibility and provide a range of contrasting values adding visual texture and definition.
White Light Standard in Time
Eventually a standard will be agreed upon that one day defines white light. Once available industry professionals and consumers will have a clear reference for a variety of light applications. With clarity comes improved understanding of how light will continue to be integrated into our illuminated world.