And it's not even technically an ad.
Artist Thomas Leveritt used a specially equipped video camera to demonstrate the UV-blocking power of sunscreen to passersby in Brooklyn, New York. The effect was dramatic. A UV filter, it seems, can make you see sunscreen in an entirely different light [Update: Leveritt has stopped by to talk about his video – look for him in the comments]:
The science at play here is relatively straightforward. The filter on Leveritt's camera allows him to capture ultraviolet radiation, which is of a higher energy and shorter wavelength than that typically visible to human eyes. There are three varieties of UV light: UVA, UVB, and UVC. The sun emits all three, though the latter two are mostly absorbed by our planet's atmosphere, which is a good thing. UVC is the highest in energy, and the most dangerous, from a carcinogenic standpoint. UVB is less energetic, but still powerful enough to damage DNA. UVA is the least energetic, and the least dangerous, of the three, but can still cause skin damage; in large enough quantities, all forms of UV radiation can lead to increased risk of skin cancer.
The association between sun exposure and cancer risk is mirrored by that between sun exposure and the formation of freckles, including – as the video so clearly demonstrates – freckles that are imperceptible to the naked eye. Freckles, after all, are just patches of skin where concentrations of the pigment melanin are high. Like sunscreen, melanin has UV-absorbing properties. Areas where UV light is absorbed appear dark when viewed through a UV-filter, which is why patches of melanin-rich skin are set in such stark contrast here. It's also why sunscreen – which absorbs UV light so your skin doesn't have to – appears black as oil.
I do have one issue with the video: I think the association that it draws between freckles and "unhealthy" skin is a touch too simple. Yes, fair skin that freckles and burns easily IS a risk factor for skin cancer, but freckles, themselves, are almost always harmless. What's more (and this, I think, is a point that always needs emphasizing): Just because you have a dark complexion or are freckle-free doesn't mean your skin is "healthy," per se, or that you needn't worry about skin cancer.
The fact is that people with dark complexions are more likely than their fair-skinned counterparts to die from skin cancer once they have it. The statistics supporting this claim can be bit confusing at first, but I'll do my best to summarize them here. First and foremost: Data from the CDC clearly indicate that white people are far more likely to develop melanoma that any other ethnicity, and more white people die of skin cancer every year than any other group. The following graphs illustrate these points rather clearly:
Look closely, however, and you'll notice that the ratio of rate of death to rate of incidence is higher in ethnicities with dark complexions. Only about 1 in 100,000 black men is diagnosed with melanoma every year, but roughly 50% of those diagnosed with the disease die from it. Compare that to the roughly 25/100,000 white men diagnosed with melanoma every year, around 4 of whom die.
All this is to say that dark skin may provide a greater natural skin protection factor than relatively lighter skin, but this should not lull those with dark complexions into a false sense of security. /pedanticsoapboxing
That minor gripe aside, the video is a powerful reminder of the UV-blocking power of sunscreen, and its utility as a weapon in the fight against cancer (for people of all complexions!). As Jennifer McWhirter – whose doctoral research centers on visual communication about health and skin cancer in the media – so eloquently put it, "[Leveritt] has unknowingly summarized my entire body of research into one very beautiful, motivating film."
BONUS: For the "super hard core," Leveritt has a longer, four-minute rough cut of the video posted on Vimeo: