Greetings all,
A lot of interesting comments here. As professional lighting designer who specializes in museum exhibitions, I thought I would post a few brief comments:
First, to
Elin Lake-Ewald: The warnings you post about LED lighting have long been invalidated by research conducted by some of the most respected conservators working in light. There are a plethora of articles and discussions to search out but, in particular, I would point you to: LED Lighting: Fact and Fiction.In the early days of the LED revolution there was, understandably, great concern, skepticism, and opposition to deploying LED sources in the exhibition settings. But time and keen scholarship has definitely shown that, when properly executed, LED lighting sources pose no greater threat to artifact degradation than conventional incandescent sources.More recently there was an article published (see above link) about high color temperature LEDS (4-6000K) being very dangerous to artifacts. But again, research has shown that these concerns unwarranted.
Museum professionals should be concerned with three metrics when exposing light to sensitive objects:
- Be sure there is virtually no UV (ultra-violet) in the beam of light.
- Be sure there is virtually no IR (infra-red) in the beam of light.
- Limit the object to visible spectrum light to exposure.
And rather than saying an object should be illuminated to 'X' number of lux (or footcandles) the better consideration is lux hours. That means an amount of light over an hour of exposure per year. For instance, we recently completed the lighting design for a multimedia presentation focusing on George Washington's tent at the new Museum of the American Revolution in Philadelphia. The conservators identified the the right balance between current audiences enjoying the artifact vs. protecting the object for future generations was 50,000 lux hours. This metric meant that if we wanted to subject the tent to full sunlight on a very bright day we could absolutely do that--but only for about one hour per year! But if we dropped the exposure to around 27 lux, we could subject the object to light for 3 five minute shows/hour for ten hours a day for the entire year and still have a significant amount of time "banked" for unscheduled viewings.) By the way, it is an awesome presentation--don't miss it!
But I digress, the original subject of this string was "what is the best choice of color temperature for light sources for exhibition?" To that I must answer, drumroll please, it depends. As has been accurately discussed in this string, the higher the color temperature, the cooler or more white the light. The cooler the light the more vibrant become blues and greens to the human eye. Conversely, the warmer the light the more vibrant become the ambers and reds. So if you were lighting Van Gogh's
Study by Candlelight and you used a 5-6000K light sources. The green jacket would be AMAZING but the face and background would be grey-ish brown with little enjoyable hue or chroma perceptible.
So, unless you are a total lighting geek and have an endless supply of light bulbs in an impressive range of color temperatures sitting on a closet shelf, what the heck should you do? Well, I recommend you take the "Mama Bear" approach: use a color temperature that is not too warm and not too cool. To my eye that is 3000-3500K (a subjective opinion.) THEN be sure you are using track lights designed to be fitted with color filter accessories. Now, rather than having dozens and dozens of light bulbs at your beck and call, you can have a few color filters to insert. What's remarkable is how little tint a filter needs to posses for it to significantly alter color temperature. A very pale amber can easily shift 3500K to 2700K; a very pale blue filter can shift 3000K to the 4-5000K range.
But, dear readers, I am not quite finished with this dissertation. Maybe someday you can catch my "What Color is White Light" talk but for now I want to be sure you also consider
color rendering which adds two important words to the discussion: fidelity and gamut. OK, if I really get into this discussion I will wear the pads off my typing fingers so, suffice it to say that not all white light LED bulbs are the same; not only can they be different color temperatures but they can render color accurately, or not. We all have stories about how green or sickly things can look under light produced by compact fluorescent light bulbs. Now those bulbs all had a color temperature rating that would be familiar to you--but they also presented horrible color rendering attributes!
And then there is flicker to be concerned about. . .
Lighting and lighting design is fascinating and fun. But one can get stuck in the weeds. Now at least you know that a seemingly simple questions has no equal answer. Good luck out there, lovers of light.
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Steven Rosen, FIALD
President & Creative Director
Available Light, Inc.
Salem MA
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Original Message:
Sent: 04-20-2017 10:51 AM
From: Elin Lake-Ewald
Subject: Color Temperature for LED lighting
We have been informed by conservators and lighting specialists that LED lights are destructive to artwork. Perhaps you should consult with knowledgeable conservators about long term effects. We are not experts on the subject, just conveyors of comments in the field.
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Elin Lake-Ewald PhD
President
O'Toole-Ewald Art Associates, Inc.
New York NY
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Original Message:
Sent: 04-19-2017 07:58 AM
From: David Higgins
Subject: Color Temperature for LED lighting
We are currently changing our lighting to LED lights we have discovered that a 5000k bulb is the best all around white light. It is bright and does light up the rooms very well and it does not hurt yours eyes like the old CFL and Florescent bulbs tend to do. Hope this helps.
David Higgins
Facilities Manager Ah Tah Thi Ki Museum
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David Higgins
Facilities Manager
Ah-tah-thi-ki Museum Seminole Tribe of Florida
Clewiston FL
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Original Message:
Sent: 04-18-2017 09:34 AM
From: Elizabeth Neucere
Subject: Color Temperature for LED lighting
I'm the Exhibits and Collections Manager at the Museum of the Coastal Bend and am working on replacing our LED bulbs in our temporary exhibit to a "whiter" light. Our current lights are 3,000K which is a warmer light. I was wondering if anyone has any suggestions on what color temperature range they'd recommend for a cooler white. I know that generally 4,000-6,500 will get you a cooler white with 6,500 being at the extreme end of it with daylight. I'm just hesitant to invest in a certain color temperature to find it to be too intense of a white.
Thanks in advance!
Elizabeth
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Elizabeth Neucere
Museum of the Coastal Bend Victoria College
Victoria TX
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