mrad
Ignoring initial beam size (i.e assuming its 0):
1 mrad = 10cm wide at 100m
1 mrad = 1 meter wide at 1km
1mrad is considered baseline for lasers.
Anything tighter is considered a higher quality system. 0.4mrad is pretty much maxed out tightest possible.
A smaller mrad beam looks sharper when you are a bit of distance out from the projector. You’re paying for the higher quality of the beam, travelling further vs its beam edge and small diameter deteriorating.
Consider too, that although a high value means your beam becomes bigger and less sharp visually, it does also mean it’s dissipating its power over a wider area, so becomes less dangerous to eyes and skin over distance (although, often over a LOT of distance!).
Beware of 1mrad specifications on low cost systems….apparently, many cheap manufacturers will put 1mrad because they assume no one will check and it can turn out its actually quite a bit higher.
Beam divergence calculators
https://www.laserworld.com/en/laserworld-toolbox/divergence-calculator.html
