Josh,
in your OP, you are writing "considering to
buy" a light meter. You have got already some answers, and there
are more in the recent history of the list. Let me turn to some
remarks near to your subject. Conversation tables should be
found in literature.
First of all: It makes sense to buy a light meter only when your museum collection (including loans) consists of object types which, for preventive conservation purposes, have to be protected against sunlight resp. UV light, in permanent exhibition, special exhibitons and storage, frequently. If you want to use a light meter only in just a few cases, you can ask a colleague from a museum in the near. Most museums owning a light meter do not use it each day, in some cases the ownership of a light meter turned to be a status symbol - like documentary cards or the worldknown outdated hygrometers.
The next importing matter after measuring
is: what are your consequences? To my personal experience, wrong
consequences hurt the objects more than the good intentions. If
you you dim down the lights continuously during daylight in
exhibitions near to nothing, visitors get angry and use the
torch function of their iphone flashlight or even the fotoflash
- and even the keenest museum warden stops prohiting that after
a few days. There are better technical solutions than dimming
down near to nothing, like light barrier sensor solutions or
modern museum LEDs.
Next: If have seen many exhibitions where
light-sensitive objects like paper documents or textiles where
exhibited in the same room together with stone or brass objects.
Of course, luminated near to nothing. For an exhibition
specialist, one of the important rules is: all light
sensitive objects belong to a special light controlled room. Do
not spread them over the exhibition.
Next: Put a signpost at the entrance (!) of
the photosensitive room that using torches or flashlight is
forbidden in order to protect the objects. This is forgotten by
museum specialists in many cases because they trust on their
wardens.
If you have to dim down the light in a light controlled room, lay much attention o the readability of explanatory texts! There are lamps without dangerous UV emittance, even small backlit texts are possible nowadays.
These are my tuppence on this.
Christian
Absolutely, Al! Measuring visible light is inexpensive and relatively easy. But measuring UV light in a museum setting (needs to be in micro-watts per lumen), as opposed to cheap sunburn meters, is a different beast. My Hanwell UV meter designed specifically for museum applications cost $1,700 for example, and there are not any that are suitable for museum purposes that are much less than that. My study was of inexpensive visible light meters costing less than $35. BTW, to convert from lux to foot-candles, simply divide by 10. This is not exact, as the actual number is 10.? but it gives a good enough approximation except for the most critical applications. So if a reading is 150 lux, it is 15 foot-candles. Or if it is 50 foot-candles, it is 500 lux. No need necessarily to have both scales on a meter.
Marc
From: ALLEN NOFTZ
Plus, do you just want to know how strong the light is, or do you want to know how strong the uv light is. Makes a difference in the kind of meter you buy. Al Noftz
On Thu, May 17, 2018 at 3:07 PM, Marc A Williams <[log in to unmask]> wrote:
Josh,Recommendations depend partially upon what your intended need will be. Are you just wanting general readings with sunlight/daylight involved, or are you wanting very precise readings inside a display case with sensitive objects? Is the light natural daylight or incandescent or fluorescent? I did an informal study of various inexpensive light meters and I can send you a copy if you email me directly at [log in to unmask].Marc WilliamsAmerican Conservation Consortium, Ltd.
We are interested in possibly purchasing a light meter for our museum. I am wondering if anyone has purchased one and has any feedback or recommendations? I wonder if there are models that measure using different units, such as lux, lumens, footcandles, et cetera? Thanks!
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