Perhaps the most important things to consider are:

1. The lighting should be as free of ultraviolet radiation as possible. Many modern LED lighting systems can provide lighting with no detectable UV. The UV component breaks down the structures that are essential to some color in moths and butterflies.

2. The essential ratio for vi light (the lighting that causes most fading of pigments) is intensity x time. This means that you can have a very low light level for a long period of time or a very high light level for a short period of time and the damage to the specimens will be the same. This means that the first question should be about the length of the display.  The second is then how low can you make the light levels and still allow people to see the exhibit well. Generally about 30 footcandles (300 lux) is more than adequate for viewers of all ages. If you create displays so that viewers have time for their eyes to adapt to lower levels, you can use lighting down to 5 footcandles (50 lux) and still have a good exhibit. Think of it as a challenge for the exhibit designer to create a "dark adapted eye" display.

5. Once you reach about 0.2 million lux hours of light (sans UV), just about anything that is light sensitive will sustain noticeable damage. That can help you define the extent of your exhibit, even at low light levels. For instance: 50 lux x 10hrs/day x ?day/year x ?years = ?

Your suggestion for viewer activated lighting is one of the best solutions! Minimizes risk while maximizing access.


Catharine Hawks
National Museum of Natural History, MRC 106
Research & Collections, NHB 394
Smithsonian Institution
PO Box 37012
Washington, DC 20013-7012
Office 202.633.0835
SI Cell 202.701.8458
CH Cell 703.200.4370
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From: Entomological Collections Network Listserve [[log in to unmask]] on behalf of Christopher Marshall [[log in to unmask]]
Sent: Tuesday, December 10, 2013 3:22 PM
To: [log in to unmask]
Subject: Butterflies on Display -- light levels

Hi all,

I've recently been asked about light levels for butterfly specimens being put on display in a public museum space.   I've been asked if there is an 'appropriate' light level that will not rapidly fade the specimen.  Has anyone in the museum display arena done a study or published recommendations for light levels that are appropriate.  My first instinct was to have lights that only come on when a viewer is in front of the exhibit or pushes a button.... so that the light was only intermittent -- but the exhibit director is not sure they can do that and so has asked if there is a lumen level that might be acceptable.

I quickly searched the ECN archives, but didn't find anything -- but if this thread was already addressed can you post a link?


Christopher Marshall
Curator & Collections Manager
Oregon State Arthropod Collection
Zoology - Oregon State University
Corvallis OR, 97331-2914
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