bad performance with land graphics set to high

[HarryKlein]

gtx 285 here ( QX9650@3Ghz, 8Go ram, playing in 1920x1200 ).

Turn shadows off and land shading to low,
the landscape will not look so nice,
but with everything else set to High I can achive 40 fps avg a low alt over the land,
and 50 to 60 fps avg at high alt over the land.

I've noticed that only the shadows and the land shading settings affect the frames rate,
setting other parameters high or low have almost no effect.