Calculating Fc from W
Posted 01 November 2005 - 03:18 PM
Posted 01 November 2005 - 05:51 PM
Posted 01 November 2005 - 06:26 PM
1 lux= 0,0929 fc
1watt= 58 cd (candels)
1 fc =(app.) 10 lux
1K @ 10 meters @ ISO 500 gives little over
50 lux = T 4.2 / T 4 (@ 24fps / 170 Shutter ANgle)
Ofcourse the formulae don't guarantee good cinematography
Posted 01 November 2005 - 06:58 PM
But to convert either watts or lumens to ft candles is a bit like converting feet to pints. They are different units that measure different things.
Foot candles measure illuminance - how brightly something is lit. That's not the same as how much light is coming from a light source. How far away is it? Where is the light directed?
Here's a link that might be useful
Posted 01 November 2005 - 10:00 PM
That rough guesstimation formula would be OK if you knew the absolute luminous efficacy of the tube and any reflector, which you don't. Manufacturers don't tend to publish the spec because it's too hard to measure and meaningfully apply; a fluorescent tube has an obscenely complex radiation pattern when considered mathematically.
Get a meter, and meter it!
Posted 02 November 2005 - 09:46 AM
This link gives me better translations for these terms than the ones I had...
Posted 02 November 2005 - 09:49 PM