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by | Dec 22, 2013 | Publications. VIX is a measure of expected volatility calculated as 100 times the square root of the expected 30-day variance (var) of the S&P 500 rate of return. The variance is annualized and VIX expresses volatility in percentage points.
How to convert luminous flux in lumens (lm) to illuminance in lux (lx). You can calculate lux from lumens and surface area. Lux and lumen units represent different quantities, so you can't convert lumens to lux. 1  Lumens to lux calculation with area in square feet. 2  Lumens to lux calculation with area in square meters. The illuminance E v in lux (lx) is equal to the luminous flux Ï V in lumens (lm) divided by the surface area A in square meters (m 2): E v(lx) = Ï V(lm) / A (m 2). For a spherical light source, the area A is equal to 4 times pi times the squared sphere radius: