Ultraviolet Safety

article by Ben Lincoln

One of the potential hazards of multispectral photography is that not only can you not see the light with your own eyes, but that light can actually cause you permanent harm.

Exposure to ultraviolet light (especially artificially-generated ultraviolet light), in particular, can result in permanent eye damage (or even blindness), sunburn, and skin cancer. It is very important that you take this warning seriously. This is not one of those ridiculous "water is known to the State of California to cause cancer" type of labels that devalue cautionary markings and/or make everyone afraid of everything.

Most people understand that extensive, unprotected exposure to sunlight can be harmful. Sunlight has already passed through many miles of the Earth's atmosphere, which filters out the worst of the UV. This is why if you find photos of hardcore mountain climbers, they often appear older than they actually are - they have spent a lot of time at high elevations, where there is less atmosphere between them and the sun^[1].

Artificial sources of UV are obviously much closer to both the subject matter and the photographer than the sun, so there is very little atmosphere acting to filter out the shorter-wavelength, more harmful ultraviolet (particularly ultraviolet-C). UV-C has such a strong ionizing effect that the main use for UV-C light sources today is for sterilization. I have read that in Russia, hospitals frequently use UV-C sterilization instead of bleach, and at least one department at the University of Washington uses it for this purpose.

UV-B and UV-A light can be almost as dangerous if not handled properly. Halogen light bulbs emit ultraviolet light in addition to human-visible bands, which is why every halogen lamp includes a glass filter over the bulb (glass blocks shorter-wavelength UV). Years ago, I read about a highschool whose gym used halogen lighting, and the glass filters had developed cracks. Even though the lights were mounted on the ceiling, tens of meters away from anyone in the gym, several teachers had developed eye damage as a result.

This article is not meant to be a definitive guide to how to work safely with UV lighting. If you are going to work with artificial ultraviolet light, do the proper research, and wear protective equipment at all times while the lighting is on. For example, this is what I look like when I'm using lighting of this type:

No Exposed Skin

Head To Toe Coverage

As a side-benefit, dressing this way means you are also ready to conduct night-time raids at a moment's notice.

Proper UV goggles are the most important piece of safety equipment. How well do you think you'll be able to continue with photography if you permanently damage your eyes? Make absolutely sure that the "UV goggles" you buy actually block UV effectively. When I first bought UV goggles, I ended up with two pairs - one made by Bouton (the Panagoggle 560), and the other made by US Safety. They appeared very similar, with both being made out of a plastic material that was the same shade of pale green in colour. However, as the following test shots demonstrate, their effectiveness at blocking ultraviolet-A light was anything but similar. I included a photo of a pair of cheap tanning goggles as well, to illustrate how poorly the US Safety goggles fared.

UV Eyewear

Bouton Goggles

US Safety Goggles

Tanning Goggles

Date Shot: 2010-03-06
Camera Body: Nikon D70 (Modified)
Lens: Nikkor-H 85mm f/1.8
Filters: Baader U-Filter
Date Processed: 2010-03-06
Version: 1.0

Bouton's staff were kind enough to provide me with transmission spectrographs of their goggles, which confirm that the Panagoggle 560 transmits essentially nothing at wavelengths shorter than 400nm. At 390nm, the transmission is 0.00071%, and it only goes down from there, staying at 0.00002% or less from 310nm to 280nm, and not registering at all from 270nm to 200nm. I got mine from Edmund Scientific for $6.95, which is a small price to pay for quality UV eye protection. In fact, at that price, do yourself a favour and buy a couple of pairs, so that if one fogs up while you are working, you can switch between them (with the lighting off, of course).

On the subject of fogged-up goggles, if you find this happening frequently (especially during marathon UV photography sessions), consider wearing a respirator under your ninja mask.

Be aware that all of this eyewear was completely transparent to near infrared light, so if you are working with high-intensity sources of that, you may need to take additional precautions.

Footnotes

The vacuum of space does not filter ultraviolet light. While the distance from the sun to the Earth makes a difference in the total amount of ultraviolet light reaching someone, it doesn't act as a filter. So the main factor in determining UV exposure is how much atmosphere (or other filtering medium) is between them and the source of that light.