I was in to UV light long before I was in to hunting, so I had all the right tools when I began to experiment with it. I did a lot of reading on studies of the vision of deer and learned they see in a spectrum that we don't, so what appears to be dark to us can be very bright to a deer.
I bought my first UV flashlight to seek out and purchase Uranium at garage sales, nothing more than a hobby, my second one was a gift from a customer. UV flashlights can "charge" glow in the dark stuff up instantly, can be handy too.
UV lights are inexpensive and readily accessible, you do not need an expensive light to detect UV. As they get higher in frequency they get more expensive, and also become invisible to the human eye, a very dangerous situation. A persons pupil will not dilate to UV the way it does regular light, although it is the one that does the damage.
I use a small handheld UV flashlight to find my arrows at night, if I lose one I simply return at dark and the fletching is easily visible at 50-75 yards.
Here is mine:

And here is what it does to standard yellow/orange Blazers:

In my gun room I have a full 4' bulb, a novelty at best. I can lay all my hunting clothes on the floor and pick out which ones need to be dealt with, the treated clothes do not show up, the ones containing UV brighteners glow as we have all seen.

Deer see in this spectrum, at least that is what my reading has been telling me, and I did a lot of reading. The first thing that comes to mind is "why was Grandpa so successful hunting in his parka, Grandma never treated his clothes!" My thoughts is simply technology, we didn't have UV issues then, no such thing as a UV brightener when Grandpa was out there. Clothes today are made cheaply and contain fabric that never before existed, it isn't comparable to the junk we buy now and then the chemicals we wash it in.
Here are some graphs on deers vision I have always enjoyed:


UV isn't a make it or break it deal when it comes to hunting, but it is a very present factor that one should make themselves aware of as more and more fabrics are blended in to our clothing.
One more arrow shot:

If you are interested in purchasing a portable UV light, here is a link to a dealer I have been using for years, you have my word he is an honest businessman and you will be well taken care of. Lots of goodies here, like replacement cords for the bows too, every color.
http://www.lighthound.com/12-LED-UV-3xA ... _2578.html