When it comes to 'hue' or color, lighting is everything. Without some form of light, we cannot see color. When lighting conditions are low, we only see ‘value,’ the lightness or darkness of an object, not the 'hue' or color.
Whether it’s yellow sunlight, blue light reflected from the sky or an orange candlelight, painters are always concerned with the 'hue' or color of the light.
Light temperature or 'chromacity' describes the 'hue' or color of light (or as viewed on a neutral surface illuminated by the light) whether it's warm, cool or something in between.
Light temperature is rated in Kelvin degrees, one of the seven base units in the International System of Units (SI), assigned the symbol 'K.' It can also be defined by using 'x' and 'y' coordinated against a standard chromacity scale determined by the International Commission on Illumination (CIE). Since 2012 all light bulb boxes are now required to tell consumers where the bulbs falls on the color spectrum so selecting the bulb color/temperature is now much easier.
Not all white light is the same, the lower the Kelvin number is the 'warmer' or more yellow the light. The higher Kelvin number is the 'cooler' or more blue the light will be. White light bulbs are usually in the middle of the scale, around the measurement of 3500K to 4100K. It's counter-intuitive, regardless of the light source because photons themselves have no heat. Not what you would expect if you were measuring a boiling pot of water or the temperature outside.
Not all white light is the same.
There's no substitute for natural light and artists love to have it in the studio. North facing windows are the preferred natural light source because these lighting conditions are the most consistent throughout the day and it allows them to get more work done using this natural lighting condition. If windows are east or west facing, the light changes dramatically throughout the day from morning until night. East facing windows see the rising sun (cooler). West facing windows see the sunset (warmer).
Too much light may be overwhelming and strain the eyes, especially if it is blasting on the white paper or canvas you are working on. You made need some blinds or curtains to control the amount of light coming in.
CRI, or color rendering index, is a numerical scale (0 to 100) used in lighting to indicate how a light source will make the color of an object appear to human eye. CRI measures the quality of light and is independent of color hue/temperature.
If you are looking to purchase lights to work with indoors, you need to determine your end goal before you choose which type of bulb. In many cases, this difference is not important. However, for certain applications such as illuminating art or comparing fabric in retail clothing stores, CRI can make all the difference. If you have gallery representation, use the same light bulbs that your representatives then you will be able to see your work in the same lighting conditions.
The higher the CRI number, the better the color rendering ability which reduces glare and will equate to sharper, crisper and more natural colored object. Light sources with a CRI of 85 to 90 are considered good at color rendering. Light sources with a CRI of 90 or higher are excellent at color rendering and should be used for tasks requiring the most accurate color discrimination.