Iph=Ev×q×Apd×QE×λh×c
Iph # current per pixel, so it is absolute value of the applied current devide by the number of pixel (1280x720)
λ # Wavelength
Ev # Input illuminance (light level)
QE # quantum efficiency (function of wavelength)
Apd # photodiode area (4.86 µm x 4.86 µm)
q = 1.6 10-19 C # electron charge
h = 6.64 10-34 J.s # Planck constant
c = 3 108 m/s # light speed
QE=IphEv×h×cq×Apd×λ
With the multimeter Iph is acquired (current divided by the number of pixels), then the ration Iph/Ev is calculated.