Miguel Bunster Posted November 1, 2005 Share Posted November 1, 2005 Hi is there any formula to calculate the Fc of a given light? I am looking into some fluorecents and cant find there Fc info all I know is that they are 40w. Is there a formula, or any way to get an idea? Thanks! Miguel Quote Link to comment Share on other sites More sharing options...
Mitch Gross Posted November 1, 2005 Share Posted November 1, 2005 Wattage won't tell you the answer because there are various coatings and gas combinations that can result in very different brightnessness. You also need to check the CRI (color rendition index) of the lights to see how well they represent the color spectrum. The bulb manufacturers usually have photometric data available either on their website or via mail. Quote Link to comment Share on other sites More sharing options...
Ozgur Baltaoglu Posted November 1, 2005 Share Posted November 1, 2005 the following is an approximation: 1 lux= 0,0929 fc 1watt= 58 cd (candels) 1 fc =(app.) 10 lux for instance 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 ;) Quote Link to comment Share on other sites More sharing options...
Dominic Case Posted November 1, 2005 Share Posted November 1, 2005 A fluorescent lamp will give you between 50 and 100 lumens per watt - depending on its luminous efficiency. 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 Answers.com Quote Link to comment Share on other sites More sharing options...
Premium Member Phil Rhodes Posted November 2, 2005 Premium Member Share Posted November 2, 2005 Hi, 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! Phil Quote Link to comment Share on other sites More sharing options...
Premium Member Laurent Andrieux Posted November 2, 2005 Premium Member Share Posted November 2, 2005 Thanks Dominic, BTW. This link gives me better translations for these terms than the ones I had... Quote Link to comment Share on other sites More sharing options...
Miguel Bunster Posted November 3, 2005 Author Share Posted November 3, 2005 Thanks for the info..I will meter it. It was just a tought but the info is great!!! Thanks! Miguel Quote Link to comment Share on other sites More sharing options...
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