Just like the meme that you should change your oil every 3,000 miles or have your teeth cleaned every six months, the photographic retailers have their own meme going – you should buy a UV filter to protect your lens.
While I am sure many of you – maybe even most of you – have fallen for this, it’s not necessary. In this post I’ll give you my opinion as to why you don’t need such a filter and further, discuss a few pitfalls of filters in general.
Let’s work backwards. Filters in general cause several problems. They may induce flare, either the visible kind that results in small starbursts of light appearing on your image, or the more insidious kind – light refraction, which ends up reducing image contrast. These problems are caused by light leaks between the filter and lens, and the inner reflective surfaces of the filters themselves, as well as a few optical phenomena, the discussion of which would be beyond the scope of a simple blog post.
Scott Bourne at Photofocus hits the nail on the head again. I always fell for this, until a couple of years ago when I decided I couldn’t afford the really expensive UV filters, read about a bit and decided they simply weren’t worth the effort anyway.
One lens I own still has a UV filter—the Sigma 10–20mm. I’m not sure why, to be honest.