Learning to see as an artist is perhaps a lifelong task, requiring countless hours of observation, comparison and reproduction of our real life subjects. This is a particularly critical process when it comes to analyzing and matching color, and the practice over time can’t be shortcut. If one is going to invest a great deal of time and energy in learning how to work with color and paint, it only makes sense to get the lighting in the studio correct right from the outset.
Daylight is considered to be the best light, especially north light (in the northern hemisphere). However, north light doesn’t remain perfectly constant throughout the day, only more constant than light from any other direction. So, artists often augment their natural window light with artificial light, and this is where things get complicated. There are many types of light bulbs sold as “natural” or “balanced” (e.g. like daylight), but not all of them deliver the color rendition quality and brightness that artists need. In our studios, we have twin banks of incandescent track lights plus twin Velux skylights, plus twin Luxo type combination lamps which can be fitted with incandescent and fluorescent type bulbs. While this is enough “horsepower” to provide adequate brightness for painting at night, the color rendition from a night of painting has always been disappointing during the light of day and has required repainting. Thus began our search for a better lamp bulb. But first, we needed to educate ourselves and understand some of the technical terms used to describe and measure artificial light.
The color temperature of lamps is measured on the Kelvin (K) scale, which is based on heating up carbon to extremely high temperatures to produce different colors. For example, carbon heated to 2426.85 degrees Celsius equals a Kelvin rating of 2700 and is yellowish-white, while 5126.85 Celsius equals 5400 K, is bluish-white and approximates noon daylight. The higher the Kelvin, the cooler the light. Household incandescents are 2500-3000 K, regular fluorescents are 4000-5000 K, and north light (blue sky) is anywhere from 7500-10000 K.
However, if one wants balanced color rendition, simply buying the right temperature bulb may not work, exactly. The reason for this is that different bulbs render the color spectrum in different amounts.
Color Rendering Index (CRI)
CRI indicates a bulb’s ability to illuminate the full color spectrum accurately to our eyes. Natural daylight has a CRI of 100, so that is what we are trying to get near to in a lamp. Bulbs with a CRI over 90 and a 5000-5500 K temperature rating are ideal for an artist’s studio.
Unlike wattage, which only describes how much power a bulb consumes, Lumens describe how bright a light actually is – its output – and are the best measure to use for brightness. The higher the Lumens, the brighter the light. Compact fluorescents and LEDs consume far fewer watts, but produce an equal or greater amount of Lumens as compared to standard incandescent bulbs. (A 9-watt LED produces 450 Lumens, the same as a 29-watt Halogen bulb).
Lux or Footcandles
Lux is the level of brightness at a particular distance from the light source, and is what really matters where the level of light on our easel or subject is concerned. (One Lux is equal to one Lumen reflected off of a square meter of surface.) Of course, the further from the light source, the lower the Lux level, but more important, light intensity (Lux) decreases faster than the distance from the light does (the inverse square law). So it is important not to place your lights too high up in the ceiling or too far away.
To read more about studio lighting and get our recommendations for which bulbs or fixtures are best for artist studios, be sure to check out Seeing the Light, Professional Lighting Solutions for the Artist’s Studio.
–John and Ann