The highest contrast ratio of the VB198TL is 50000000:1. That's over two times the contrast ratio of the most frequently found dynamic contrast ratio of 20000000:1. Across all flatpanel monitors that have been around for more than a year the contrast ratio ranges from Mega Contrast to 100000000:1.
It may also be worth considering one of the alternative LCD screens that have a 50000000:1 dynamic contrast ratio currently available including a cheaper flatpanel monitor such as the Asus VB178D or you might consider a higher rated flatpanel monitor such as the VB199 (£122.84), or the VB198T (£130.87) both from Asus.
If the contrast ratio of this flatpanel monitor is too low for you then you might also want to look at the Asus VX207NE (£65.98) (100000000:1 and cheaper).