orthographic

orthographic lenses are a type of fisheye lenses

orthographic lenses are also called” hemispherical“or “orthographisch
orthographic lenses use an image mapping function of type
r = f sin \theta

maintains planar illuminance
[table caption=”orthographic angles” width=”500″ colwidth=”50|50|50|50″ colalign=”center|center|center|center”]
weak,medium,strong,max
66,90,120,180
[/table]
hemi180[1]

An orthographic / hemispherical fisheye, uses a parallel projection of a hemisphere onto a plane. The resulting image will obviously be circular. The widest view angle is 180 degrees. At +/-90 degrees extreme distortion will occur. Due to this heavy distortion it’s less often used than f-Theta / angular fisheye.

see:
fisheye types