The Acer S220 has a maximum contrast ratio of 100000000:1. That's over five times the contrast ratio of the most common dynamic contrast ratio of 20000000:1.
This PC screen's contrast ratio (100000000:1) is actually the best contrast ratio across all medium monitors that have been available for a similar time to the S220.
The worst contrast ratio across similar types of PC screen is Mega Contrast.
We think you might also be interested in some of the alternative PC screens that have a 100000000:1 dynamic contrast ratio currently available including the Acer V226 ($125.99) which has a better Rating; or the Acer G226HQL ($69.99) which is cheaper.