Does anyone know or have a source on how fluorescent materials in hi-viz perform?
I've looked at various standards and done a fair bit of research so far but nothing seems to outline just how it performs...
Not quite sure what you meant by "perform", but there is great difficulty in relating the photometric performance of fluorescent materials with how it performs in terms of safety. The standards for hi-viz safety clothing do not really do this, instead they limit their scope to the minimum necessary to be able to manufacture products with predictable performance, with little explanation of their specifications.
The basic research behind safety clothing tends to be very practical i.e. how much sooner can a fluoro sample be seen by young/old people at certain times of day? There are too many other factors e.g. what is the visual background, how bright is it, etc. that the topic defies straightforward analysis.
...
As we all know, the fluorescent properties of the clothing reflect ultra violet light in a wavelength that falls into the visible spectrum, which as such makes the garment appear brighter than other objects.
But how much of the ultaviolet light does it reflect back?..
The human eye is more sensitive to some colours than others, does not perceive different brightnesses in a linear manner, and moreover does not perceive different colours at different brightnesses uniformly. Suffice to say, a fluoro orange item will appear brighter than a flat orange item, especially at dusk, but it would be meaningless to say it is 1.5X or 3X brighter.
Here is a paper that covers road signs, which is similar enough to clothing, that gives you some idea of the complexity involved:
http://people.usd.edu/~schieber/nas/fluorence/fluorence.PPT
Fortunately, if you are interested in human perception of fluoro, the human eye is quite good at assessing it
.
...Does it only work on a certain range of ultraviolet?
Sort of, but the sun is a broadband emitter of many UV wavelengths, and the relative proportions of each wavelength reaching ground level varies according to geographic latitude, time-of-day and weather. Part of the magic of fluoro is that there is a lot of UV light at dusk/dawn, because UV bends more readily over the horizon than visible light.
