In what circumstances should I use a UV filter?

[KSeet]

My Hoya seems uncoated. Exactly like a mirror, only its see-thru. Reflection very very strong.

By the way, my UV filter is named UV GUARD. Any idea?

 

[Zerstorer]

I find that Hoya HMC/Ultra/SHMC/Pro1 UV has a yellowish tint, whereas B+W MRC does not.

Try overlay the filters on a white piece of paper, you will see what I meant.

Strange, mine is the opposite. The 010 Haze MRC has a warmer tint compared to the HMC UV that I have.

Anyway, just compared the reflections if anyone's interested. MRC and SHMC both have purple reflections and the HMC has green reflection. Purple sure looks a lot nicer and classier.