How flourescent colours work

[Bluebottle]

Why hi-Vis glows:
It causes a colour shift and reflects blue/ultraviolet light back as yellower/whiter, boosting the yellow so that it glows brighter.


During a search I came across a comment that flouro yellow doesn't work in twilight because it can only be lit by the light that falls on it.

In fact flouro colours reflect more visible light than their surroundings and they work better as the light begins to fade.

That sounds impossible, where does the extra light come from?
It comes from a colour shift. When various colours hit a flourescent surface they are bounced back as a different colour - multiplying the brightness of that colour making it appear unnaturally bright and intense. Flouro yellow steals extra light from other colour frequencies and sends it back out as yellow. In bright sunlight the effect is less pronounced because our eyes are flooded with bright light. When the light level drops the contrast is much more obvious.

You can sometimes see this in nature when white flowers seem to glow at dusk.
Many insects see in ultraviolet and what we are seeing is the edges of ultraviolet dayglo.
To bees and other insects these flowers are lit up with a landing strip and markers pointing to where the goodys are.
Humans aren't very sensitive to blue and ultraviolet (that is why there isn't a dayglo blue for humans).

It is also the way "optical brighteners" work in washing powder to "make your whites whiter". They shift light from the ultraviolet spectrum closer to the visible spectrum to boost the white (and light you up under a nightclubs UV light.

I don't care whether people wear it or not, your choice - but let's not make stuff up and pretend its science

[gn2]

I know nowt about why hi-vis works but in days gone by I worked as traincrew so I know this...
You can see trackworkers from a mile away if they are wearing hi-vis jackets.

[horobags]

Nevermind hi vis mark, how do I get this to work??
http://www.maxi-muppets.co.uk/forum/vie ... =5&t=15813" onclick="window.open(this.href);return false;

[Bluebottle]

Hang on, I'll get me glasses

[horobags]

Read your advice on the other topic, cheers mark.