My accountant told me I had to wrap everything up today to take the tax write off on business expenses so here goes:
Let's take an Avigilon 4K PRO camera, 35mm sensor, Canon glass;
It claims minimum illumination of 0.1 lux.
Then let's take a Canon(or compatible) SLR/DSLR 35mm sensor with TTL metering.
Point the camera at the subject and adjust the FOV to match the desired subject. Let's say for example this is a parking lot and we are interested in capturing cars coming thru a one lane choke point from some distance.
Frame a given subject using the DSLR, e.g. Gray mid-size car, during the low light period.
Set the metering mode to the whole FOV. Set the ISO to 100. Let the EV compensation adjust both aperture and shutter speed.
Using the cameras values calculate luminance using the standard photographic formula:
Luminance = 12.4 x fnumber^2/ (exposure time x ISO)
So for instance if the camera says f/2.8 and 1/30 sec that's ~160 lux reaching the sensor.
If the calculation gives you 1 lux, and the Avigilon spec is accurate, you will know that the Avigilon camera, with the same lens and FOV, is capable of detecting the car, at least in the best case scenario.
Honestly, it's just a theoretical stab in the dark, but you (possibly) have all the equipment, I would be interested in what the method yields vs the actual camera.