Color balance of UV filters.
It is true that today’s digital cameras can achieve white balance that is neutral in even extreme conditions. But white balance and a full range of color and subtle color relationships are not the same thing!
The yellow cast of one filter is evident below; this is why I recommend the B+W line from Schneider optics: their UV filters are dead-on neutral, both by eye and as measured using my Gossen Color Pro IIIf color meter. Shooting with a yellowish filter like that on a beautiful blue water or reflections of the sky are a really bad idea.
The image below was shot in sunlight, but tungsten lighting produced the same results: the Hoya Ultra UV(0) filter imparts a strong warm cast by attenuating (cutting off) deep blue. Compare the spectral transmission graphs of the B+W 010 to the Hoya HMC Super UV0, and observe how deep blue is attenuated by the Hoya.
The attenuation of blue might be OK when the goal is to cut atmospheric haze, but the rest of the time it means you’ll lose a chunk of the deep blue color you might be after; it’s a loss of intensity and a shift in color rendition of blue. It also means a loss of light (eg slower shutter speed): think about shooting in the shade or high in the mountains in the shade.
Even if white balance is adjusted, it is still an overall approximation which cannot restore the original color relationships: the attenuation of blue light subtly changes those color relationships.
If color is important, it’s probably not a good idea to mix and match brands of filters when consistent color is desired between lenses. That is why I have standardized on the B+W line.