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Sunday, March 29, 2015

UV Photography

Exploring light wavelengths beyond what our eyes can see constitutes an interesting domain, because in a scientific perspective it can reveal characteristics of the imaged objects, that our eyes and/or visible light based cameras cannot see.

For example UV photography can reveal the story of our skin. Solar UV burns leave scars that are practically invisible to the naked eye, but through long wave ultraviolet these are clearly distinguishable from untouched skin (for example see http://www.huffingtonpost.com/2012/06/22/cara-phillips-ultraviolet-beauties_n_1606131.html)

While not having specialized gear for UV photography I decided to give it a try with a UV power LED that I had laying around:



Given that the LED puts out a not entirely eye safe ammount of UV light (275 mW - see http://www.led1.de/shop/lng/en/prolight-power-led-uv-ultra-violet-275mw-13-watt.html), I have not neglected the shades:


These are regular sunglasses, which normally do a good job at attenuating UV light. Empirically I could verify the shade produced on a UV fluorescent material, providing good evidence that UV light would be blocked by these:


While I did not have the necessary filters to block visible light and let just the UV light pass, nevertheless I managed to achieve interesting photos with the characteristic contrast on the surface level details of the skin (UV light does not penetrate the skin like visible light does). There is always stray visible light from multiples sources of fluorescence, that help soften the image, effectively countering the high contrast result that we are interested in:










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