In this third and final installment of a series, we’ll delve into the world of ultraviolet (UV) photography.
In part one we discussed the light spectrum, why “full spectrum” is a misnomer (I call it wide spectrum in these articles) setting your wide spectrum camera so that it can again be used as a visible light (VL) camera, and band pass filters.
In the second part, we discussed using long pass filters and infrared (IR) only filters.
UV photography is as different from IR photography as IR is different from visible light (VL) photography. It’s much more complicated and a bit more expensive. And UV photography is simply not as easy as IR photography. The main difficulty with UV photography is that for the last few decades, photographic equipment manufacturers have done their best to reduce, or entirely eliminate UV light from photographs. UV light causes haze and reduces sharpness in a photograph and that’s generally not appreciated.
When you photograph with IR or VL with a wide spectrum camera, you usually only need to put on an appropriate lens filter for your lens of choice and you can begin snapping away. That does not work with UV. For example, B+W sells their 403 filter that is advertised as one that passes UV light. This is true, it does. However, it also passes IR light while blocking VL, where as a typical lens with multi-coating blocks UV light only. If you simply mount the 403 filter on your lens, you end up with what amounts to a black and white IR image. This was my original idea when I first tried UV light photography. But, it did not work and it turned out to be the very first step in a long learning process. There are various issues involved in getting UV light photography to work, and hopefully some of the things I ran up against, which I will discuss here, will alleviate some frustrations that might cause some to walk away from what can be rewarding photography.
As you may recall from part I, UV wavelengths run from ca 10nm (nm=nanometers) to ca 400nm, whereas VL wavelengths run between 400nm and 700nm. We humans can see light at wavelengths down to about 380nm, more or less (some individuals with an eye condition called aphakia can see even further into the ultraviolet band, and it’s been described as a “blue-violet glow”). Some birds and insects can see light at about 300nm. UV goes opaque to the atmosphere at 200nm.
There are two basic types of photography that can be done with UV lighting. The first type people often think of is fluorescent UV. This is usually done in a dark room, with a “black light” type device, and the glow off the lit subject is visible and can be photographed as such. This is recording visible light. The second type is reflective UV. With reflectography, you light things the same way, but you put filters on your lens that block VL and IR. Reflective UV is the usually invisible light that the wide spectrum camera can record.
The best light source for UV is bright sunlight. Failing that you can use specialized lighting. Maxmax.com has a wide variety of UV lighting supplies. They are very specialized, but you can also buy simpler ones from other vendors such as Amazon.
UV light is a bit on the dangerous side. It can cause sunburn, and it can cause eye damage if you are careless. So, if you are going to work with artificial light sources, you should always exercise caution and use eye protection. Figure 1 shows some simple light sources and a protective pair of glasses that you must use if you are going to be working with UV. These types of glasses are not expensive. Never look directly at any UV light source.
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