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Monday, August 12, 2013

••◊ Exposure to Foot-Candle Conversion

I saw an interesting formula posted on Roger Deakins' forums yesterday and decided to store it on my blog for future reference.  The formula converts exposure parameters (aperture, ISO, shutter speed) to required foot-candles - a common parameter of professional lighting fixtures.

foot-candles = 25 x (T-stop)^2 / (ISO * shutter time)

So if I'm running at T4, ISO 800, and 1/48th shutter, then I require 25 foot-candles of light to get standard exposure.  For me, this really helps to know which lights I need to drag onto set to get exposure.

Credit goes out to David Mullen, ASC for posting this formula.

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