The Lenovo T2324 has a maximum contrast ratio of 3000000:1. That's 40% less contrast ratio than the most frequently found dynamic contrast ratio of 5000000:1. Medium monitors that are a similar age to the T2324 dynamic contrast ratios range from Mega Contrast (worst) to 100000000:1 (best).
It may also be worth also looking at one of the other PC monitors that have a 3000000:1 dynamic contrast ratio currently available including the HP ProDisplay P221 (£129.99) which has a better Rating.
Flatpanel monitors with a higher contrast ratio that might also be worth considering include the 23MP57 (5000000:1), or the 24MB37PY (£140.34) (5000000:1) both from LG which is also cheaper.