How to convert between lux and exposure value?

Question

How to convert from an exposure value to lux? Thanks!

i.e. what's the formula behind this chart?

Answer 1

Forget the math on Wikipedia. By inspecting the table to which you linked, it's possible to see a pattern:

EV      Lux
-1      1.25
-0.5    1.75
0       2.50
0.5     3.50
1       5.00
1.5     7.00
2       10.00
2.5     14.00
3       20.00
3.5     28.00
4       40.00
...

1 EV is 5 Lux. 2 EV is 10 Lux. 3 EV is 20 Lux. So, it looks logarithmic:

lux = (2 ^ ev) * 2.5;

(2 to the power of EV, times 2.5)

C-like:

#include <math.h>

double evToLux(double ev) {
    return pow(2, ev) * 2.5;
}

Update

Wikipedia has this formula:

Update 2

It is important to point out that EV is dependent on the film speed (ISO). All above is true only for ISO 100. It is easy to convert to other speeds, though: EV(at ISO 100) == EV(at ISO 200) - 1

(H/T Nikolai Ruhe)