I've changed from a DS-2Cd2342WD-I (with latest firmware v5.5.82 build) set at highest quality, 15fps, H264+ ON, Bitrate of variable and with everything else at default (did a reset), which gave the following night time image
to a DS-2CD2385-FWD-I (firmware is latest at v5.6.5 build 200316)...