Anyone know a general way to calculate the f stop of a given light if all you know is the Lumens at a given amount of feet/meters? given a steady speed and iso rating?

I am trying to determine the ratings of some constant light sources and many only have lumen, or lux.

Thanks.

Stephen Eastwood
http://www.Stephen Eastwood.com

Stephen,

Take a look at this and see if it's what you want:

http://www.answers.com/topic/foot-candle?cat=health

It's a great question though for sure.