Own there spec pages it says.
DS-2CD2385FWD-I has a 1/2.5" Progressive Scan CMOS
DS-2CD2142FWD-ISB has a 1/3" progressive scan CMOS
DS-2CD2342WD-I has a 1/3" progressive scan CMOS
So some of the cams that are now 4MP have the same size sensor as before but some are listed at 1/2.8"...