Check out the C|Net HDTV Picture Settings forum here:
You might try doing a search using PN42B450 or PN42B451 (the U.S. equivalent, since that's what the reviewers typically post).
If none exists, you can start one. Unfortunately, "optimal" settings have variables, including room size, color, amount of ambient light, etc.
I have a samsung ps42b451b2w t.v and would like to know what are the best picture settings for my t.v