Any way to improve the night vision on these cams with a software tweak?
I'm not aware of any software improvements, but adding an external IR illuminator can improve the DCS-942L Night Mode brightness and viewable distance. I have a DCS-932L, which is of the same generation as the DCS-942L, and a DCS-5020L located in the same room. The light cast from the DCS-5020L IR illuminator significantly improves the DCS-932L Night Mode image brightness and viewable distance when the DCS-932L is pointing towards the DCCS-5020L.
BTW compared to the 5xxx series cams, the night vision on these seem horrible.
I'm not sure you're making a fair comparison. The DCS-5020L was released over two years after the DCS-942L, during which time D-Link made significant hardware and software improvements. These two models are several generations apart.