The highest contrast ratio of the Acer S271HL is 100000000:1. That's over five times the contrast ratio of the most common dynamic contrast ratio of 20000000:1.
This PC monitor's contrast ratio (100000000:1) is actually the best contrast ratio across all medium monitors that are a comparable age to the S271HL.
The worst contrast ratio across similar types of PC monitor is Mega Contrast.
We think you might also be interested in some of the other flatpanel monitors that have a 100000000:1 dynamic contrast ratio currently available including the Acer B236HL (£139.98), or the Asus VN279 (£239.14) which has a better Rating.