To filter or not to filter, that is the question. Photographers will argue until they're blue in the face about the issue of using protective filters. Luckily, Lens Rentals is here with science to tell you exactly how good a slew of options are.
Many photographers swear they'll never put protective filters on their lenses, while many others claim a nice filter can save you from a much costlier repair should something go awry. To examine the quality of such filters, Roger Cicala and the team at Lens Rentals tested a wide-ranging set of them for their light transmission and surface flatness. While we all know the importance of light transmission, the inverse property, reflection, is equally important: the less transmission, the more reflection, and the more reflection, the more ghosting, glare, and loss of contrast you can expect. In addition, the team also examined the surface flatness of the filters: the less flat an optical surface is, the more the light that passes through it can be distorted, causing image quality issues. And while most of the more expensive filters performed well, you'll be pleased to hear that there are some more affordable options that performed admirably, so check out the full post for more and grab a protective filter if you feel so inclined.
I use them exclusively for protection.
I'm a fan of lens hoods, personally.
Lens hoods for me. Unless I'm shooting in a harsh, dusty etc condition or need a ND filter for an outdoor situation, I avoid. I wonder how many pixel peeper trolls who always pop their heads up on photo forums have filters on their lenses.
I quit using filters when I dropped my camera and the filter shattered and scratched the hell out of my lens. No filter is better than that. I'll use specialty filters but they aren't attached permanently.
I love Roger's work. He's the only person doing some of the things that old Modern and Popular Photography used to do when they disassembled cameras and lenses to tell us what they were made of and how they were built.
But in this case, he's only telling us part of the picture. We already know that for "protective" filters we're looking for filters that "first, do no harm." And it's always great to get more information about that on individual filters.
But just as important (maybe more important) in the concept of "protective filter" is if and when they do any good, what they do good for and what they don't do good for.
I got a significant bit of education from the guy on YouTube who ran tests dropping a calibrated weighted steel rod smack into the front elements of a series of lenses and discovering that the front elements of modern lenses are astonishingly pretty danged tough...and tougher than filters. Striking the front elements of even cheap lenses with the steel rod left them not only unbroken but even unscratched--but shattered filters.
His tests convinced me that protective filters are useful when I can expect a lot of ballistic crap in the air (like ringside at a rodeo--literally, ballistic crap in the air), but not so useful if I think I need protection from actual physical impacts. In that case, a hood still reigns supreme, and a filter might even be counter-productive.
Only put a clear filter on my lens for protection when the likelihood is something will be hitting the surface of my lens at high velocity. Almost always windy days at the beach, but occasionally when shooting street art festivals when I'll be getting right up in the artists business and spray paint is being used liberally... Or if people are throwing things... If I feel I need eye protection (or head protection) for myself, then a filter on the front of my lens is the least I can do. Otherwise my lenses go naked.