I don't have the best computer, so I have to play on low graphics settings. (everything on POOR, and at 720P)
When I use optics, and scopes with illuminated reticles, the reticel becomes all blurry and hard to aim with! Especially with the M4 Acog. (also, Kobra, M68 optic, but not PSO, or PU)
This seems to be very bad, until you go up to medium graphics settings, in the SCENE COMPLEXITY settings. Where it is fixed, and okay.
*also* this is also extremely bad when using iron sites, because of the depth of field on iron sites, the blurriness makes it almost unusable.*