It seems that the varifocal has a bigger (when number goes down, that means bigger right?) aperture than the fixed lens S3 cameras. From what I know (not much) that is the opposite of the predecessors.
5442H is special version of bullet where 5442 is inside bigger chassis and optics with F/1.2 from Ultra line (7442H)...
Normal bullet is 5442E - where chassis is smaller, designed for Pro 5xxx line and optics with F/1.8 for varifocal (F/1.6 for fixed lens).
Both variants are with IR lighting.. Difference between F/1.2 and F/1.8 is almost 2x more light per pixel.
Models with aperture F/1.0 and white light were always named as 5449 (last digit is sensor/optics/lighting spec).
Yes I known - there was 2-3 models with F/1.0 named as 5442 in the past.
Dahua for some time didn't quite follow their camera model coding rules.
But it looks like they want to fix this mess.
At this moment 5449 line is based on old S2 WizMind series (Volt chipset)..
Dahua didn't presented a new WizMind-S 5449 line for now...
The new S3 WizMind-S is based on a new chipset which gives more power / functions. There is much better minimal Illumination spec for new F/1.8 5442-S3 WizMind-S (0.0007/0.0004lux) cameras comparing to old F/1.8 5442E-S2 (0.003/0.0003lux) ones . Question is they used a new better image sensor or there is only difference in image processing?
F/1.0 creates a problem with shallow depth in fixed lens cameras (bokeh effect). A new F/1.6 or F/1.8 WizMind-S S3 have better minimal illumination spec that old one (even with F/1.0) - so they didn't needed to use F/1.0 with a new model. And fixed problems with shallow depth.