Glossary
Nits
The unit used to measure display brightness; one nit is one candela per square metre.
A nit is a unit of luminance, equal to one candela per square metre. It measures how much light a display emits, and it is the figure manufacturers quote for peak brightness.
Why the numbers look so high
A display in glasses is projected onto a transparent lens and competes with whatever is behind it. Indoors a few hundred nits is ample; in tropical daylight the same image is invisible. That is why wearable display brightness is quoted in four figures where a phone screen would not need to be. Peak brightness is also usually a maximum the display can reach briefly rather than a level it sustains, and running near it costs battery.