There's an option to scale 1:1 instead of Fill fullscreen, so it wont stretch the image. 

^^ woops. i dont think it was possible. are you sure its 1080 config?
as far as i can recall there's no 1:1 for 1080 resolution.. only 720p (on dell 2407)

plus only 2405 can do that 1:1 properly.. the newer 2407 cannot perform this feat. and on the bad side is 2407 is using various panel providers (its not single sourced from one vendor). so your quality can be hit/miss depending on the source.

again i could be wrong as im not using dell.