Treesmakemelag

i get about 30-60 fps(everything on very high) when running around but when i aim down the scope with an acog or just zooming in on trees my fps drops down to about 20 fps, Making aiming almost impossible. and thats even with Proper very low vegetation also. is there anyway to fix this? Even If i turn everything on very low i get like 200 fps but when i look at trees i drop with about 30-40 fps! Startup Parameters -winxp -cpuCount=4 -maxmem=2048 -exThreads=7 Game Version 1.57.76815 Nvidia Control Settings off off off off none off all 3 Singe Display Prefer maximum perfomance on allow perfomance on on off force off Spec Intel Core i5 750 @ 2.67GHz Quad Core 4 gig ram nvidia GTS 250 1 Gig