Outputting 1920x1080 iMac to a 720p tv

[Color09]

I have an HDMI cable connecting my 21.5 inch 2010 iMac to my 42 inch plasma 720p Samsung tv. the picture looks slightly pixelated on the tv, is there any way to fix this? I get these two windows when I go to the displays settings:
http://imgur.com/3DZqXEB

Whenever I change the "optimize for" option it changes on both windows. Is there something wrong with the tv maybe?

 

[Dandu]

Try to optimize for the Samsung, and use 720p. But what's the real definition of the TV ? Many Samsung plasma TV use a 1 024 x 768 panel withe rectangular pixels and a scaler to accept 720p or 1080p content.

Try to use the native definition, it's the best way.

 

[26139]

Mirror?

Try not mirroring?