Forget Visible Light! – Let’s Talk Infrared and Ultraviolet

In this post, I explained how the light spectrum that is detectable to our eyes runs from around 400 to 700 nanometers. The sensor in your typical digital camera can detect light waves from around 200 to 1,000, but it has a hot mirror filter to block out the light waves at the extreme ends of the range. Then, in this post, I showed what happens when you remove that filter from a point-and shoot. I also told you that I ordered some ultraviolet and infrared LEDs. On my last post, Mark comments that perhaps I could use a cellphone board camera or a I2C camera, as these seem to register the infrared light in a remote control. Let’s explore that a bit.

The ultraviolet LEDs I ordered are claimed to be 395 to 400 nanometers in wavelength. Lights in this wavelength should produce very little visible light if any at all. I think the manufacturer fudged the wavelength specs just a bit, as these shine quite purple to the naked eye. I have no doubt that they are producing quite a bit of UV light though. Without the proper tools to accurately measure wavelength output, I’d guess that the range on these is more like 395nm to 405nm. When I take a test shot of a UV LED shining on my wall with my unaltered AW100, you can see a blue hot spot but the rest of the frame reflects visible light.


The same shot with the full-spectrum Olympus comes out in a neon purple bath:


I have a little glass horse that sits at my workbench. This is a reproduction of a design that Jennifer’s family came up with generations back. This one was cast in vaseline glass, which is a bright green, uranium filled glass that emits a bright luminescent glow under an UV light. Here’s how it looks with the visible light camera with the UV LED on it:


And again, through the unfiltered eye of the Olympus:


The visible light green glow is rather shocking against all of that UV light! As Matt mentioned, a digital camera can ‘see’ the light emitted from the IR LED in a remote control, but it can’t see much of it. Check out this side by side between the modified and unmodified cameras:

The infrared LEDs arrived today, and here is one shining on my wall through my stock Nikon:


Clearly, there’s not much going on there. Near the center at the bottom of the frame, note the faint red glow of the LED itself. These are even less visible to the naked eye. Through the UV-seeing Olympus though:


We get quite the wash of fuchsia. Just for giggles, what effect, if any will the IR light have on the vaseline glass horse? Here it is through my Nikon:


It wasn’t completely dark, but it was dark enough in the room that the camera didn’t want to focus. But through the Olympus:


Here is a picture of the view screens of both cameras, pointed at the horse, with the IR LED trained on it:


Microcosm Overlord and I are going to build a dual IR/UV light array that I can tote around for some further testing instead of being stuck at the bench. I fully expect to have some fun results to share. With any luck at all, perhaps I can have the array usable in time for Phlegmfest!

5 thoughts on “Forget Visible Light! – Let’s Talk Infrared and Ultraviolet

      • Things like this are why when my eight year old daughter came up to me and said

        “Dad, I want to build a potato cannon”

        my response was “You came to the right parent!”

        $30 later shes got a nice 6′ spud-zooka (that she named the potato-inator) that chucks those things around 2-300 yards burning isobutane and di-ethyl ether.

  1. I have a business and have looked all over for a light like you have is there any way you can tell me where you got it.

    thank you

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