High quality & also cheaper UV filter and lens cover

One thing first: I use UV filters generally as a lens protector for the outer objective lens (front glass) to (scratches etc.) protect them from damage and dirt. The filter (technically correct: the filter) is therefore permanently screwed onto the lens.
The contrast-enhancing effect of a UV filter (if at all noticeable) is of secondary importance to me.
But now the Hoya HMC UV filters in 58mm version:

The filter is multicoated (HMC) and Hoya-typical meticulously crafted. The overall height (without lens thread) is 4 mm and shows on my standard lens (18-55mm) no vignetting (vignetting). Juicy charge on an extra-flat filter (eg Hoya Pro1 Digital MC) you can save this reason - except to use extreme wide-angle in 17 / 18mm.
According to a UV filter in comparison Internet cuts this filter from the test winner and at the same time price-value for money. Even more expensive filter from Hoya (eg HMC Super UV 0 - I have 3 pieces), B + W (010M MRC) etc. are not better, according to this test - why therefore pay more? The transmittance (light transmittance) is the visible light (wavelength 400-700nm about) more than 97%, UV light is almost completely blocked.
This also shows the practical test - a reduction in light intensity is practically not recognizable through this filter. The increase of contrasts is only minimally to recognize when shooting outdoors.
An indication yet for Product name: Under this order (. ASIN: B00009R9A1, Model No. 0690, No. Y5UV058; applies exemplifies the 58mm version) gives a Hoya HMC UV 0 filter. There is also a more economical version, namely the Hoya HMC UV-C filter. But these filters (according to label) not the entire UV light out, but only the range of 100-280nm (UV-C). The UV-0 version filtered according to test a wider range to 390nm. FYI: CCD / CMOS sensors operate in a range of about 200 to about 1100 nm). At the same price I would therefore be sure to buy the UV-0 version.
In conclusion, I can recommend this filter to 100% because it acts as a good lens protection, does not cause visible and significant limitations of Bildquälität and even increases the contrast with "hazy" visibility conditions at best. Therefore, a recommendation as basic accessories for each lens.

Addendum: A note still for cleaning up: So far I have yet to remove any contamination on my Hoya filters with special lenses / glasses cleaner and a microfiber cloth. So this "lack" of other reviewers I can not confirm. Of course, this depends greatly on the dirt and the type of cleaning agent to from: aggressive media can "eat" into the coating and this can not be removed then. As with many optical surfaces Again, less is often more clean, since every cleaning process additionally burdened the coating.

Update 23/10/2012: A note regarding cleaning. The cleaning works properly and quickly with the Hama Lenspen, which I describe uA in another review.

Update 9/12/2013: The surest, how to recognize the filter sold, the manufacturer Item!
For the UV (0) filter is this: Y5UV0xx (xx = diameter in mm); the UV (C) filter has the following designation: Y5UVC0xx. Please be careful especially in "suspicious" great deals! In most cases the UV (C) variant is sold! As a "rule of thumb" will cost the UV (0) variant 30-40% more than the UV (C) variant