Tiffen makes good filters and bad filters. The good Tamron lens uses multicoated glass. Since you describe the filter as ‘glary’, I think the filter you originally had was not multicoated. With the newer cameras coming in above 5Mpixel, they are more sensitive the the quality of glass that you use. Non multicoated filters will have internal reflections between the glass-air boundaries on both sides of the glass. This will soften edges slightly, reduce the sharpness and reduce the contrast of the image.
Going from the clear glass to single coat makes a huge difference. To some extent, filters are a bit of a racket. There is considerably more coated glass, more expensive glass shapes and types of glass in a lens than the equivalent dollar amount of coated glass filters. Tiffen is not the least expensive for equivalent type/quality of filter. Other filter manufacturers:
Sigma, Hoya, Heliopan, B&W.
Sigma filters are hard to find, not many places seem to carry them, though when I find them, they are very good quality for the price.
Other aftermarket lens manufacturers(In order of the quality I have discovered in using them):
Sigma, Tokina, Tamron
When picking up Sigma lenses, only use the EX style, and only US market – not gray market.
NOTE: The camera manufacturer lenses by Canon, Nikon and Sony seem to have fairly good quality but I have also noted problems with some of the Nikons. I have less experience with the Canon, though I have heard good things about their ‘white’ lenses (and seen). Be wary of the ‘kit’ lenses on D-SLR cameras. They are generally not worth the money. If you look at the mount on most of them, it is a plastic mount, not a metal. These lenses are cheaply made. Buy the body only and pick a quality lens from aftermarket or from the camera manufacturer. NOTE: I don’t have much experience with Olympus and Pentax lenses so I can’t comment on these, though Pentax does have a good reputation going way back to the 60s.
APO lenses are always better than non-APO (APO = apochromatic). I would recommend always using an APO when going above 8Mpixel with an APSC sensor or 16Mpixel on a full-frame sensor D-SLR.
