Apologies if the title of this week's column is a little crude--it's attributed to Ken Rockwell, a no-nonsense photographer who gives very useful practical advice about gear and techniques on his site. In this case, Rockwell was referring to a UV lens filter for DSLRs, which he says doesn't have any optical benefits for today's cameras. It's a topic we've broached before--whether or not a UV filter is necessary at all. Photographers are split into two camps in this debate.
The first camp believes that UV filters not only are optically useless, but unnecessarily degrade the quality of your images. Putting a piece of flat glass, no matter its build quality, on top of a $2000 lens is going to affect the quality of light hitting the sensor. UV filters were originally designed to block out wavelengths of light that can't be perceived by the human eye, but affect film. Ultraviolet light on film can leave a haze effect and reduce contrast, but this effect doesn't apply to modern digital cameras, which compensate for UV in the sensor and image processor. So for DSLRs, the purpose of UV filter is now primarily to protect the front element of the lens from any potential damage. In fact, when you buy a UV filter from a company like Tiffen, the image on the box shows a cracked lens--the manufacturer doesn't hide behind the fact that UV filters aren't really for UV protection.
But damage protection is exactly what the second camp feels is necessary about using a filter. That extra insurance against dropping a lens element-first into the ground warrants what they consider negligible image quality loss, which makes sense if the camera is being used for web photos or is equipment on loan, like shared office equipment. UV filter users believe that lens resale value is higher with a UV lens, too. It's the photography equivalent of putting a plastic screen cover on your new smartphone.
With my two lenses, I wanted to see for myself not only if having a lens filter/protector significantly affected photo quality, but also if there were any noticeable differences between a cheap UV filter and a more expensive one. I bought two filters to test: a dirt cheap $9 Tiffen UV filter, and an expensive $70 B+W UV filter with "multi-resistant coating". But as of today, I'm ditching the Tiffen filter and going to use the B+W filter on new lenses.