When you zoom in on grass with a scope (RCO for example) your frames drop instantly, instead, if you stand at the exact same spot and zoom with Mouse2 your frames are stable and accepteable.

Suggestion would be to change the way the scope works, instead of zooming, maybe render the image and it's surrounding when available but do not "unrender" the rest or it would take too much to render again. This would allow for precise shooting in less than 50m without lag from foliage.

The lag could be due to ATOC and PPAA or FSAA.