Distortion - Pincushion And Barrel With 2 Irises
To show pincushion and barrel distortion.
Bright point source with condenser lens, ground glass screen, coarse mesh, iris, 8 cm focal length lens, and second iris.
The optical system in the photograph includes the following: bright point source with condenser lens, ground glass screen, coarse mesh object, first iris, 8 cm focal length lens, second iris, and distant screen. Closing the first iris (preceding the lens) causes barrel distortion, while closing the second iris (following the lens) produces pincushion distortion. ◙This is not a bright display, but can be seen in a large room and is closest to the theoretical description of distortion.
Arthur S. Jensen, Lens Aberrations - A Classroom Demonstration, AJP 13, 113-115 (1945).