Stephen Eastwood , Jul 11, 2007; 01:18 a.m.
Is there any way to determine the F stop at a give iso and given speed and given
distance of a continuous light source based on the lux or lumens or footcandle
rating?
Thanks for any help on this.
Rainer T 
, Jul 11, 2007; 05:52 a.m.
Here's a little table to convert Exposure values to Lux.
From the EV, you can easily work to a speed and f-stop pair.
Sam Thompson , Jul 11, 2007; 06:09 a.m.
Couldn't you just use a meter built into the camera?
Here is a wiki article on foot candles that shows you the aperture values at a given foot candle.
http://en.wikipedia.org/wiki/Foot_candle
Here is a chart on what EV values are given a foot candle or lux.
http://www.fredparker.com/ultexp1.htm#evfclux
As I understand it. A 1000 lumen lamp has the intensity of 1000 lux at 1 meter, and at 2 meters 250 at 4 meters and at 4 meters 62.5 lux using the inverse square rule.
So at 4 meters from the light source it's 62.5 lux which is about a 4 or 5 EV value.
From there you can find a EV to iso/aperture/shutter speed calculator and find out that its f/2.8 at 1/30 at iso 800.
Helen Bach , Jul 11, 2007; 12:50 p.m.
"A 1000 lumen lamp has the intensity of 1000 lux at 1 meter..."
One lux is one lumen per square metre. Converting from a lamp's output to lux requires some information about directionality and about the properties of any reflecting or diffusing surfaces as well as distance information.
Is it worth mentioning that EV alone is not a measurement of brighness? You need a combination of EV and ISO for example, such as the commonly used 'EV at ISO 100' (as used in the tables that are linked to above).
