Article: What to look for in a painting light

Hi all,

Hansrainer here :)

this is probably more a of a beginners topic,
but across the different communities, the question with which light to paint keeps coming up regularly and  while most people have some idea what lamps to buy, they often don’t fully understand why.

Coming from a scientific and technical background, I think we will always be better at what we do, if we actually understand why certain things work and others don’t as well. So today, I will take a small excourse into lighting. This text is by no means exhaustive and just touches the surface of the topic, it should however provide a solid foundation for what to look for in lighting for artists.

To give a brief excourse: When buying a painting light, there are two major qualities that we have to look at: Light Temperature and the underlying colorspectrum of the light-source.

Light temperature:

The temperature of the light is usually provided in degree Kelvin (°K) (it actually corresponds to the color of a piece of iron (a black body) heated  to that temparature). Usual livingroom-lighting is between 2400 and 3400K, its spectral peak is close to the infrared part of the spectrum and light looks “warm” and yellowish. Studio lighting and “Daylight”-Sources usually have a light temperature of 5000k and above. It is perceived as “cold” and blueish compared to the warm light sources and its closer to the temperature provided by the sun throughout the day. Depending on light source the spectrum peaks usually in more than one wavelength. Actual sunlight can vary widely between the low 2000s and way above 6500 depending on the time of the day, suns inclination and weather conditions.

It’s pretty much common standard accepted amongst painters that a good painting light is similar to daylight of a neutral day (not high noon, lightly overcast etc.) and thus in the Range above 5500k.

The implications of light temperature on painting are easy to understand and visualised; If you look at something under a yellowish light-source, it causes the colors to look different compared to a whiter light source:

5500°K - "Daylight" 

3000°K - "Warm" Light

And of course - the same holds true if you paint under warm light and then display in daylight.

Light emission spectrum:

The underlying spectrum is a different issue. In order to understand this, we need to know two things:

What we perceive as white light, daylight, is a whole continuum of light of different wavelengths, the sum of which we perceive as white. That means, white sunlight contains light of all colors of the spectrum (red, blue, yellow, orange and whatever else you can imagine).

When we perceive an object to have a certain color, that is because it mainly reflects light of this specific color. E.g. If we see something red, this means the objects absorbs the vast majority of light frequencies, except red and reflects therefore only red light.

From that follows: In order to perceive for example red properly, we need to look at it using a light source that contains sufficient red light. If we were to illuminate a red object with monochromatic light, e.g. blue, the object would not appear red but rather a greyish blue, since there is little to no red light to be reflected.

Red light component reduced via photoshop

 Full spectrum light 5500°K

So, a good light source provides sufficient amounts of light of the color we want to paint with - and since we want to create a natural rendition and our object to look according in natural light, the closer the light source is to sunlight, the better.

Considerations for paint-lighting sources

If we are looking for an ideal light for painting (and taking photos!), we want both factors, light temperature and color spectrum to be close to natural (sun)-light.

For the color spectrum, this is usually determined using the value CRI (Color Rendering Index).(more details can be found here: https://en.wikipedia.org/wiki/Color_rendering_index). This value basically describes how close the spectrum of a given light-source is to the spectrum of our sun.

A CRI of 100 means that the spectrum is equivalent to a perfect black body (aka the sun, tungsten lamps), an average fluorescent tube is somewhere between 80 and 85, a run of the mill LED is below or at best close to 80 and full spectrum tubes and LEDs, manufactured for professional photographers, print-proofing facilities and art restauration labs are between 95 and 98. Usually the deviations are mostly due to a reduced red-component in the light. (Which makes sense energetically: Red light is actually warmer, more energy is "wasted" as in converted to heat instead of visible light, the reduction in the red, long wave spectrum makes a bulb brighter and thus more energy efficient).

The effect of a low CRI vs. a low color temperature is more subtle - its not like the stark yellowing observed in warm light vs. cold light but rather colors looking  slightly off by nuances, most likely colors in the red spectrum, where usually cheaper LEDs and tubes tend to have a weakness.

So, when shopping for a painting lamp, aiming for a daylight lamp is always a good idea, but if you are staying in the energy-saving area, springing the extra money (or just looking a bit longer) for an option with a high CRI is not gonna hurt your color-representation and photos either. At least in relation to regular daylight.

In addition to these factors, its important to also have ENOUGH light. The more light we present to our eyes, the better the quality of our perception. You will actually see more if you use strong vs. weak lights - this holds especially true if you use additional tools like magnifying lenses. These enhance the resolution of what we see, but to function properly, they need even more light than the naked eye.

One relatively cheap source of good lighting is bulbs for growing plants or terrariums, another but more expensive is looking into lighting for photography. In my next article I will present you with a simple tutorial on how to convert an old Tri-Tube Pro Painting lamp into a state of the art illumination device, using a video illumination LED-Panel.

I hope this article is of use to you and you found it interesting
- let me know in the comments below.

Yours,
Hansrainer