If you’ve purchased a camera or lens in the last fifty years, there’s a decent chance you’ve been urged to add a UV filter to your purchase. Buy online, and you can expect instant discounts on filters as add-on items. Buy in-store, and you’ll find them bundled with everything from cleaning kits to memory cards. However, many question whether there’s any actual science behind these recommendations—or if they’re due merely to the insane profit margins to be had from a piece of glass.

The truth, of course, is hidden behind some hazy myths and misconceptions.

A History of UV Filters—What the Film Era Left Behind

Believe it or not, ultraviolet (UV) filters weren’t created as a point-of-sale item or a clever way of profiting from melted-down milk bottles. Rather, they were created based around a very legitimate need: while human eyes aren’t very sensitive to detecting UV light, photographic film remains highly sensitive to it, making outdoor footage susceptible to haziness and bluish tints.

(Note: human eyes aren’t sensitive to actually seeing ultraviolet rays, but they are quite sensitive to being burned or blinded by them—so do invest in UV protection for your eyes, particularly when filming at high altitude, where ozone protection thins, or around reflective surfaces such as snow or water.)

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To prevent the ruin of our precious film reels, the UV filter was introduced as a means of blocking ultraviolet wavelengths—and all was well up until the turn of the century, when digital sensors began to rise.

Ultraviolet Light in the Era of Digital—Pixels Versus Film Cells

You’ll likely find a lot of people who insist UV filters are necessary to protect digital sensors from the same haze and tint that used to plague film cameras, but you won’t find a lot of scientific proof to back these claims. The truth is that the sensors in today’s digital cameras are not tangibly sensitive to ultraviolet light, which makes threading a UV filter onto your lens about as necessary as handling your memory cards only in darkrooms.

In fact, it’s possible for these filters to do more harm than good nowadays, particularly when using inexpensive filters. Tinting and softness are hardly an issue with premium filters. However, any material you place in front of your lens can still theoretically degrade your image quality, merely because you’re adding another layer between your subject and sensor. If you’re paying for premium glass and coatings in your lenses, you’ll want to do the same when it comes to filters; otherwise, you stand to handicap your equipment by shooting through inferior glass.

The larger issue has to do with reflections; the more surfaces you have between your sensor and a subject, the more opportunities you create for flares and reflections, particularly when that subject is backed by strong direct light. Of course, chances are your lens has close to a dozen internal elements as-is, so adding a filter doesn’t add risk where it doesn’t already exist; it merely adds a little more—which might actually be desired. (See below.)

If not, you can always lessen that risk by stopping down (increasing your f-stop number) in the presence of direct light.

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Filtering Visible Harm—Why Filters Are Still Handy

While there are clearly reasons against putting a $50 filter in front of a $2,500 lens, there are also reasons in favor of this, most of which revolve around protecting not your images, but your actual lens.

A built-in benefit of filters is that they act almost like an invisible force field to protect your lens against environmental dangers, and you’ll find it’s far preferable to accidentally smudge a lens filter than it is an actual lens. Filters are much easier to clean and many, many times cheaper to replace. Plus, they protect against more than just liquid and fingerprints—but also slight impacts.

Finding Clarity—Filtering the Pros and Cons of UV Filters

At the end of the day, it’s probably best to look at UV filters more like shoot-through lens caps than actual light filters. They won’t affect your images much, if at all, for better or worse; however, they might protect your lenses—and your sanity the next time you shoot out in the elements or film near children with wandering fingers extended in the direction of your precious lens.

Matt Siegel writes about stock footage, film myths, and the pros and cons of UV filters for VideoBlocks.