Matching north light with fluorescent bulbs

[Marvin Mattelson]

Sun-a-lite makes a bulb that is 6500 degrees Kelvin with a CRI of 98.

Actually Sun-a-lite sells the bulbs. They are made in Germany and Sun-a-lite is a dealer. I have ordered these bulbs and will post the results when they arrive.

[Timothy C. Tyler]

Sounds like none of us are ready to trust those selling to judge how true their product is. The trouble is that we can't easily compare "stereo A" with "stereo B" which is always very informative when comparing other products. Holding a white card up doesn't really do it either.

I wonder if the curve here is lower than we suspect. When you wish to insulate your home once you pass R-value of 38, any improvements are moot and certainly a poor investment. North light in Iceland in April is very different from North light in Madrid in June. I rather think that if we can get from 5500-6000k, even if this involves mixing of bulbs, then that is likely as good and certainly more constant than northern light which we all concede varies.

On a related subject, too much light in a studio is wicked. Photograghers measure "how much" light all the time. Seems we painters should ask this question too.

[Marvin Mattelson]

Tim I am happy to report that your theory doesn't apply to light bulb manufacturers. I just received the bulbs I ordered on Friday. The name on the bulbs is Lumichrome made by Lumiram. They are spectacular. In comparison Ott lights are too green and Ott true color are too yellow. They are not precisely the same as true north light but are so close that the difference is negligible, to my eye anyway.

In addition I've never seen any lights that are better.

Here is the description from their site:

Lumichrome

[Timothy C. Tyler]

I bought some too. I like them. Two things though. Imagine one room lit by 5500k lights and one lit by 6,000k lights. Without seeing the print on the bulbs can you walk from one room to the other and tell one from the other?

Our eyes adjust like digital cameras and declare "okay, this is white etc. What's that feature called on a digital camera where it reads the light source and adjusts? Secondly, and more important, what happens to the work when it's sold? Maybe (at best hope) 4000k halogens or worse if it goes to a museum with really weak light from 30 or 40 feet away. The museums sometimes use good light color but it's often to far away.

[Marvin Mattelson]

Tim, the fixture I use in my studio uses six bulbs on two separate circuits so I can flip on three of one type of bulbs and then flick them off and flip on the other type.

The difference is very discernable.

I don't worry about the light my paintings are eventually going to hang in. If it harmonizes in my studio and my values hold it will read wherever it hangs. Also, if you paint a painting geared to a particular color temperature of light what guarantee do you have it won't be moved? The old masters painted their pictures in their north studio light, which is one of the primary reasons for my quest to find a better bulb.

However, since I want to insure that my paintings look good on the wall, I recommend a great picture light made by fineartlight.com. They custom design their fixtures for each painting. Another fabulous product and definitely worth every penny.

[Valerie Warner]

Hey Marvin,

My concern here is not only my paintings but my health. I was using regular ol' fluorescent bulbs. I found that they offset the gold, pine wood ceiling I have. But then, I remembered the health effects of those lights when used alone for long periods of time. I was wondering if you still like the afore mentioned lights and do you think they have close to the full spectrum of color in them which is said to be very beneficial to our health?

I'm hoping if I have enough of them and they are positioned advantageously I will not have to worry about that yellow ceiling or even my gray-green walls. What do you think?

Thanks for your help!

[Marvin Mattelson]

Val, the lights I use are full spectrum. There are many degrees of color rendering accuracy in the full spectrum area. There is a designation called color rendering index or CRI. If a bulb is rated over 90 CRI it's considered full spectrum. The Lumichrome bulbs I use are rated at 98 CRI, the very highest available. Daylight is rated at 100 CRI.

The color of your ceiling and walls shouldn't matter as ling as the bulbs are in white fixtures. If the lights are reflecting directly from the ceiling you would need to employ some sort of reflector housing to eliminate this since the color of a reflective surface will compromise the color temperature of the bulbs you use.

Hope this helps.

You might want to bring some photos of your studio to Atlanta and we can discuss this further.

[Valerie Warner]

Oh you are the bomb! That makes it very clear. I was not giving any credit to the housing/reflectors that the light is mounted in and I will make sure they are white and wide to throw lots of the CRI 98 light.

I will bring pictures of the studio to Atlanta, thanks!

[Tom Edgerton]

Marvin--

I've always understood the temperature of a north light to be around 6500K to 6800K, approximately in the middle between a regular fluorescent light and 5000K.

I've used the Lumichrome tubes in the ceiling of my studio for years, supplementing my northwest window, and found them to be generally very good. However, a complicating factor for me is that when I paint under any single overarching wavelength of light all day, my eyes get tired, especially at night--to the point where color discernment goes completely South. So I've used a cheap reflector on a stand and bounced another wavelength--sometimes regular tungsten household bulbs, sometimes the Sunwave corkscrew bulbs, sometimes blue-coated bulbs (whatever feels right)--off of the ceiling into the overall Lumichrome illumination. It's really just a "trace" of another wavelength, but the mixture helps immensely in avoiding the eye fatigue over long sessions.

Thanks as always for your thorough research and generosity in sharing it.

Best--TE

[Marvin Mattelson]

Tom, I haven't experienced the eye fatigue you describe, but if I do I'll certainly apply your remedy. I'd never have known about this solution if I hadn't shared my knowledge first. What goes around comes around. Thanks!