shadows off-dubbled my framerate!

[David198502]

hey guys!maybe for most of you its common knowledge already.but for me it was very surprising.
since the very first day, i played with shadows on,because in the manual its stated,that turning shadows off,just leads to a minor increase in performance.
today i played with my video settings again,because i wanted to be able to fly a self made mission over london with ~30planes.before that,it was impossible for me because i got about 18fps over london sightseeing mission with the previous settings,so i decided to tweak them.
the more i turned my settings down,the more fps i got.but to really be able to have smooth fights over london,i had to turn almost everything on the lowest.....result=it looked like crap and far worse than il2 1946.
i became frustrated and turned everything back to high,except resolution, and decided not to "visit" london anymore.
but then i turned only the shadows off and left everything to high.
i was amazed how smooth it felt suddenly.so i tried my mission again.the result was that now i can play that mission with about 30planes with an average fps of 35.with the same settings and shadows on i get 11-15fps average.
didnt think that shadows have such an big effect on performance.maybe this feature is possible to optimize?!

systemspecs:
-Mainboard S1156 INTEL DH55TC,Micro-ATX,bulk
-Prozessor INTEL Core i5-650,3,2GHz,LGA1156,Dual-Core,Boxed
-2x 2GB DDR3 RAM,1333MHz,CL9,KINGSTON ValueRAM
-PCI-E 2.1 SAPPHIRE Radeon HD5570,Lite Retail,Low Profile
-Windows 7Home Premium 64Bit