d12e8b4e_sic_Dome_projection___Domerama__Spherical_mirror
[0] Brightness [Fisheye] Reduced brightness of the projection due to light passing through a fisheye lens. [Spherical mirror] 
Because a spherical mirror only reflects off a mirrored surface, it loses little brightness.
Geodesic Dome projection » Domerama
Spherical mirror