Using a special UV filter, a photographer shows people just how much cumulative sun damage adds up over time.

Just how much sun damage do you have? A video posted to YouTube last Friday still has millions of viewers wondering. For "How the Sun Sees You," photographer Thomas Leveritt taped people with his camera using the ultraviolet spectrum, which can reveal damage that hasn't yet surfaced on the skin.

One by one, participants in the video are treated to a view of their faces in this special camera filter. The results are shocking—even those with outwardly perfect and unblemished skin found patches of sun damage lurking beneath the surface.

"It's no gimmick," says Debra Jaliman, MD, a New York City-based dermatologist and author of Skin Rules. "You're seeing irregularity in the pigment of the skin you wouldn't see to the naked eye." In fact, some dermatologists have similar cameras of their own in their offices to educate patients about sunscreen use, she says.

The best part of the video: seeing just how powerful sunscreen really is. As the people smeared sunscreen on their faces, solid black warpaint-like markings appeared on their skin. "The sunscreen is filtering the UV and blocking it so that the camera doesn't work," Dr. Jaliman says.

Many of the people shown in the video weren't wearing sunscreen, but even those who spend very little time outdoors should wear it every day. "Just being out 10 minutes a day, you're still going to get cumulative sun damage that builds up over time if you're not protected," Dr. Jaliman says. And whether it's 5 or 10 years from now, that damage will eventually be visible on your skin.

Learn more about sunscreen strategies and formulas to help protect your skin from damage, and make sure you're not making one of the 15 most common sunscreen mistakes.

Watch the video: