Here we see a photobombing trick, used by Harley Davidson.

They achieve to incrust a logo on a photo you take. The logo is invisible with naked eyes and only revealed on the photo you take.

How does it work?

  • Tip: view the front of your remote control through your camera while pressing the buttons. You can check the batteries this way too. – Chloe May 21 '14 at 22:31
up vote 21 down vote accepted

The camera in a smartphone is sensitive to wavelengths of light that the human eye cannot see. Have a look at this picture from this article:

Spectral response

This is actually a Canon EOS 40D SLR, but the idea is the same. The human eye can't see any wavelengths longer than about 700nm, but the graph shows the camera can detect light out to 1000nm.

So if you project your message using light with a wavelength of, for example, 900nm your eye won't be able to see the message but the camera will, and it will appear on the photo.

  • 2
    “The camera in a smartphone is sensitive to wavelengths of light that the human eye cannot see.” A bit nit-picky, but lots of digital cameras—not just SmartPhone cameras—can see IR light. – JakeGould May 21 '14 at 13:02
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    As a practical test, use the "live view" on your favorite digital camera to look at the signal LED on any infrared remote controller as you press a button. The camera will show you that the LED blinks, even though you can't see it naked-eye. – rob May 21 '14 at 13:40
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    Another interesting question would be why digital cameras are sensitive to non-visible light, considering that the usual purpose of digital photography is to reproduce the perception of the human eye. – Philipp May 21 '14 at 15:53
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    I was always under the impression that all consumer cameras had IR filters explicitly for filtering out that light. I guess those filters are not as ubiquitous and/or sharp as I thought. – user10851 May 21 '14 at 17:25
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    An important but crucial (maybe obvious to most, but not some) detail here is that you see the IR message on your screen because the screen is emitting the IR message it sees in the visible (some people might ask "alright, well why doesn't the screen show the message's light in the IR also?"). – YungHummmma May 21 '14 at 17:53

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