The trick here is that
foot-candles (or lux, an alternative light intensity measurement) depends upon
the distance from the light source. Intensity falls off with the square of
the distance. Thus, if the intensity is 100 foot-candles at 1 foot, at 10
feet the intensity will be 1 foot-candle. It will be 10 foot-candles at
just over 3 feet from the light source. So, the answer to your question is
nonsensical unless it also specifies the distance away from the chamber
fireplace. Of course, as you are aware, fire intensities vary greatly
depending upon their size and the stage of burn they are in. You will need
a light meter to replicate this within reason, but you can often find them very
inexpensively. A bought a few a while back for $19.95 each - cheap
Chinese made units, but they worked fine for needs such as
yours.
Interestingly, these
issues are not a factor when considering sunlight. The distance from the
sun to your building's window (how many millions of miles is that?) is
statistically the same as that distance with the extra 30 feet added to it that
the sunlight has to travel reach the interior of the building, thus the light
levels are the same (ignoring the loss created by penetrating the glass).
93,000,000 miles = 93,000,000 miles + 30 feet within many, many decimal
places.
Marc
American Conservation Consortium,
Ltd.
4 Rockville Road
Broad Brook, CT 06016
www.conservator.com
860-386-6058
To Museum-List
Does anyone know the range of foot candles that would be
given off by an 18th century chamber fireplace? The historical
society I work for does not have a light meter and we would really like to add
some appropriate lighting to a program we are developing. I realize that it
will depend on the size of the fireplace and room, but a general estimate
would be fine. Additionally, if anyone knows approximately how many watts this
would be, I would be very grateful. Thank you in advance.
Suzanne
Buchanan, Director
Hingham
Historical Society
P.O.
Box 434
Hingham,
MA 02043
Phone:
781-749-7721
Fax:
781-749-0091
http://www.hinghamhistorical.org/
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