Lux and lightmeters?

1. Is it possible to measure light output of up to 100,000 lux with a

photographic light meter?<br>2. How can I 'convert' the lightmeter

reading into lux?<p>I have searched the archives and found several

references, but none seem to answer my questions.<br>Can anyone help

please?

I'll quote what I read on the net. Can't remember who wrote it though.

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<I>Under restrictions of measurement-method and sensor-sensitivity, for 100 ASA and a direct (non-reflective) light reading:

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Light intensity (Lux) = 2.5 x 2^EV - Or vice versa: EV = log (Lux/2,5) / log 2

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Example: 10000 Lux => EV = 12, which equals 1/125s @ f5.6

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For those wanting to avoid EV, and get straight aperture/time combinations: Light intensity [Lux] = 2,5 * aperture^2/time

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Enter a preferred aperture or time, and with a given Lux you can calculate time or aperture.</I>

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I also found this explaination...

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<I>A foot-candle is equivalent to one lumen per square foot. A wax candle flame has a luminous intensity of approximately one candela. If you hold the candle one foot away from a surface, the illuminance of the surface at this distance due to the light from the candle will be approximately one foot-candle. It will be 1/4 fc at two feet, 1/9 fc at three feet, and so on in accordance with the inverse square law for point light sources.</I>

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The manual for a Sekonic L-408 lists the following:

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<I>Luminance (cd/m^2) = .125 x 2^EV"</I>

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After messing with this for a bit I discoverd that the "carrot" symbol is used to designate "raised to the power of." (Math is not my long suit.) Also these calculations are set for 100 ISO.

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Most light meters will give you an EV reading, so it's not too hard to figure it out from there. I just created a little EV to Lux chart that I need when checking lighting levels in offices. That was a lot cheaper than buying a dedicated Lux meter.

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I believe that 100,000 lux is a little over EV 15 at ISO 100. Well within the parameters of most light meters.