I will try my best to answer this. I will first explain that there is a difference between LV, EV and Lux.

LV: Light Value is a simplified figure of Lux and is an industry standard. Please refer to the table below:

LUX     LV
10240   12
5120    11
2560    10
1280    9
640     8
320     7
160     6
80      5
40      4
20      3
10      2
5       1
2.5     0

EDIT: It seems I had this very wrong. I have updated it.

Camera manufactures generally use a light box at the value of 12 for adjustments. So, the light value for 12 is 12,000 Lux.

Lux: Lux (as quoted above) is a unit of measuring light, or luminance. Please refer to the table below:

Examples

Illuminance        Surfaces illuminated by:
0.0001 lux         Moonless, overcast night sky (starlight)[3]
0.002 lux          Moonless clear night sky with airglow[3]
0.27–1.0 lux       Full moon on a clear night[3][4]
3.4 lux            Dark limit of civil twilight under a clear sky[5]
50 lux             Family living room lights (Australia, 1998)[6]
80 lux             Office building hallway/toilet lighting[7][8]
100 lux            Very dark overcast day[3]
320–500 lux        Office lighting[9][10][11]
400 lux            Sunrise or sunset on a clear day.
1000 lux           Overcast day;[3] typical TV studio lighting
10000–25000 lux    Full daylight (not direct sun)[3]
32000–130000 lux   Direct sunlight

EV:

Exposure Value is really Exposure compensation. If you change this value, you are not changing the Lux being shone into the camera. The only way to change the Lux is to change the lighting.

Above, you saw before that the Light Value and Lux are related. Now I'll go into more detail of the LV.

For a camera to be exposing correctly, it is said that it must have the following consistencies:

   LV       = 12 (or 10,240 Lux)
   ISO      = 100
   Aperture = f5.6
   Shutter  = 1/125

For repairing and adjusting cameras, the light boxes are valued at LV and temperature. LV is just an industry standard to simplify the Lux value. If you want exact measurement, a lux meter would be your best bet.

While the above table is also a standard, it may vary camera to camera (probably not more than a stop. I haven't done enough testing, though). If you're trying to calculate the LV/Lux, it'll be best to look at the Lux table above.