UV light is very hard on the eyes. Using it even briefly will cause a lot of eye strain and can cause permanent damage if used often enough. Best saved for very brief and very occational bursts.

Blue is close to UV on the spectrum. Many blue LEDs also put out a fair bit of UV.

I've tested my 10 color LED light on the blue setting with urine and it glows pretty good as long as it's dark out. If I ever need to track somebody through my bathroom who has a bladder control problem, I'm set!

Well, there is tonight's experiment!

Arthur from The Sacramento Tracking and Wilderness Training Group pointed out the many animals,including deer, can see UV. He pointed us to this site which explains most clothing uses UV brighteners that make us stand out to animals:

http://www.atsko.com/articles/hunting/how-game-animals-see-smell.html

"...the deer has only blue peaking and green peaking receptors while the human has a third receptor..."

I have always wondered, how do they "know" that the receptors in a deers eyes work the way that the ones in human eyes work? They may be right, but to me it is just another SWAG. After all, they can't ask the deer...

Pay no attention to the electrodes in your head, deer.

Well, after several non-scientific experiments my conclusion is that colored light can aid in nighttime / dim light tracking. For me a red and green combo was easiest on the eyes and tracks were readily seen shadow-defined shapes. Using white light destroyed night vision, and using red only was not as easy on my eyes or as effective.

I hope to try UV soon.