Question about IRLED. 5.4mW vrs 5.4mW/sr

Hi,


I was looking through some IRLEDS trying to find the brightest one when I came across two different unit of measurements. mW and mw/sr. I came across a led that was 80mw/sr thinking that was really bright but then I noticed most of the other leds were like 10mW without the "/sr". My question is whats the difference?

thanks.

more accurate designation, particularly with IR
not just electrical usage, nor brightness at axis
imagine a cone of light beginning at a point and increasing to 8% of a sphere at 1 meter radius
that area is a steradian
the light energy is watts per steradian or w/sr

cool so a 5.4mW IRLED is the same brightness as a 5.4mW/sr IRLED?

could be on axis
may not be at angle to axis
example: laser, bright on axis, not bright at angle to axis