Suzanne,

This is a complex question with many variables as even the type of wood and
how a fire is stacked and built can have a profound effect on how much light
is emitted. And translating the foot candles into watts is tricky. Because
the watt in a light bulb is a measure of electrical energy and does not
translate well for luminance. I checked on this and 1 foot candle equals
0.0000015759751708 watts per Cm squared. Already too much math for me!

Your best bet is to build a fire, ask a staff member or friend who has a
photo meter to take a reading off of a surface in the room that you want to
illuminate (and yes, that can be a face!) - this should give you a
semi-quantitative read on how much light energy you are looking at, based on
photographic exposure parameters.

It depends on what sort of fixtures you are thinking of to replicate this
period lighting effect -  but I would simply get a fixture and try several
different bulbs until I approximate the "mood" - you will probably have to
use incandescent bulbs if not more on the red side of the color temperature
to approximate illumination by fire. Then once you have that dialed in then
double check it with the same photo light meter and that should give you an
approximate value to compare.

Cheers!
Dave

David Harvey
Conservator
Los Angeles, CA

PS - I once did a whole run of installing digital candle systems in 18th
century chandeliers - a great resource for lighting in historic houses is
still the 1999 APT Journal on the topic.


On Tue, Jul 15, 2008 at 12:49 PM, HHSDIRECTOR <[log in to unmask]> wrote:

>  To Museum-List
>
>
>
> Does anyone know the range of foot candles that would be given off by an 18
> th 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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