Different manufacturers play ‘Specmanship’ when it comes to the low light performance (LUX level).
The f-stop should be measured at F1.4. This is how wide the lens iris is open to let light in.
The IRE is often not stated at all, indicating that the specification may not be accurate and should be questioned.
A typical figure is 50 IRE IRE is a unit used in the measurement of composite video signals. Its name is derived from the initials of the Institute of Radio Engineers. A value of 100 IRE was originally defined to be the range from black to white in a video signal. A value of 0 IRE corresponds to the zero voltage value during the blanking period. The sync pulse is normally 40 IRE below the zero value, so, peak to peak, an all white signal should be equal to 140 IRE.
An IRE measured at 10 will give a much better LUX rating but the image will have no contrast definition between black and white.
