|Besides offering full 1080p resolution the LNT4665F also features a 15,000:1 dynamic contrast ratio for rich blacks and subltle tecture display
The key word there is dynamic. In other words, it is the difference between the brightest part of the screen showing all white, and the darkest part of the screen when showing all black.
In other words, you will never get that high a contrast ratio with a single image. In fact you probably won't even come near it(Don't count out a difference of a factor of 10:1 or more). I can't find any numbers that measure it without the dynamic contrast on.
To be honest the first thing I do on a TV these days is turn off dynamic contrast and similar technologies. I find them WAY to distracting when watching movies, and I am not really a videophile I don't think. I would much rather set up some decent settings by hand and not deal with the backlight turning up or down as the video dynamics of a movie kick in.