External monitor = blurry fonts

Hi,

Im quite satisfied with my first OSX product, a macbook pro 13". But i want to use it mainly with my 27" external Samsung LCD, which is

quite frustrating as the fonts are totaly blurry compared to Win7.

Things of interest:

Macbook Pro 13" Mid 2012

OSX = Montain Lion 10.8.2

Adapter: Official Apple Adapter mini-dvi -> HDMI

Ext.Monitor resolution: 1920x1080 native

Tried changing the fonts with Tinkertool

Tried changing the font smoothing via System settings and Tinkertool

Tried changing my monitors settings (AV/PC, sharpness, etc)

On the macbook everything looks fine.

Any hint?

Thanks

Phil