Ahh hi! Nice to see you here too

As for filters, if you want to use best to use a multicoat filter. Any single coat filter even from Kenko, Hoya and B+W (do they have single coat filters?) will not be good and just introduce additional flare. IMO the best price/performance ratio would be the Hoya HMC series, its a multicoat and is pretty decent.

I always heard of f/1.8G being much sharper than f/1.8D. I purposely buy a 1.8G to carry around during Super GT, but performance was not what I wanted . I decided to check the focus with a focus test chart and decided to do a comparison with my f/1.8D as well. Surprised the outcome is similar in terms of sharpness! My DSLR was mounted on a tripod while doing this comparison side by side.

Below are some samples 1:1 cropped. D700 mounted on tripod, shot in JPEG L fine AWB. Guess which is 1.8G and which is 1.8D?