Hi there!
Wandering through MD screening options i've found strange dot shape: HDM_DoubleDot.

I've played with it a little and discovered that it literally reduces the size of the halftone dot, thereby doubling effective LPI value. Am i correct?

The second question is - what it is for, for god's sake? I think maximum of 300lpi, that can be selected in output plan options, is enough for every imaginable task