The Acer B193 has a maximum contrast ratio of 100000000:1. That's over five times the contrast ratio of the most frequently found dynamic contrast ratio of 20000000:1.
A 100000000:1 dynamic contrast ratio is actually the best contrast ratio amongst all PC monitors of a comparable spec and age to the B193.
The worst contrast ratio amongst comparable types of PC monitor is Mega Contrast.
It may also be worth considering one of the other PC monitors that have a 100000000:1 dynamic contrast ratio currently available including a cheaper LCD screen such as the Packard Bell Viseo 193DX or you might consider a higher rated LCD screen such as the Acer 196L ($98.99).