Nidelva river through Trondheim Norway

Nidelva river through Trondheim Norway
by Saaru Lindestokke                

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I meter a surface at ASA 100 and get F4 at 1/15 second. What is the illumination coming off that surface in Cd/square foot ?

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marked as duplicate by Itai, AJ Henderson, dpollitt, mattdm, John Cavan May 27 '13 at 0:43

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

1  
Probably best asking this on physics.stackexchange – MikeW May 26 '13 at 0:00
    
Maybe How to calculate Lux from EV? – mattdm May 26 '13 at 4:43
    
I think the linked question contains the information you're looking for. – John Cavan May 27 '13 at 0:44

This Kodak reference for estimating luminance and illuminance may help.

Your metering at ISO 100, 1/15th and f/4 would be equivalent to ISO 400, 1/30th and f/5.6 if I've done the math correctly. So use their value for f/5.6 which is 2.67 Cd/ft2

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