The highest contrast ratio of the Acer 192HQL is 100000000:1. That's over five times the contrast ratio of a 20000000:1 PC monitor, which is the most common contrast ratio.
This PC monitor's contrast ratio (100000000:1) is in fact the best contrast ratio amongst all comparable spec LCD screens that have been on the market for a similar time to the 192HQL.
Amongst similar types of PC monitor the worst contrast ratio is Mega Contrast.
There are a number of alternative flatpanel monitors that have a 100000000:1 dynamic contrast ratio currently available which you might want to look at including the Acer V196 (£59.99) which has a better Rating; or the 206HQ, or the K192HQ both from Acer which is cheaper.