I've just bought a second hand (great condition!) KDL-40W3000 which is also my first LCD TV. Overall I'm very pleased with it except for the fact that gradations (transitions) don't seem very smooth

Here's a quick Photoshop example of what I mean where the first image shows a smooth transition from black to white:

However, the image below has a much more uneven transition, like I see on my TV:

It seems to be most noticeable in shadows where the unneven smoothness makes them "dirty" looking. I've tried changing all sorts of settings but haven't succeeded in fixing the issue. I also reset the TV after buying it in case the previous owner had messed things up.

I never had any such problems with my old CRT type TV (also a Sony).

So is this something I should expect from an LCD TV or might I have missed a setting (or rather a combination of settings it would seem as I've tried everything)?