Additional Info

• ID Code: L6-40
• Purpose: Fast and simple way to show pincushion and barrel distortion.
• Description:

  The optical system in the photograph includes the following: bright point source with condenser lens, 5cm focal length plano-convex lens with flat side toward light source, copper wire screen, and 10 cm diameter 23 cm focal length convex lens. The image of the wire mesh is cast on a screen at about 10 feet from the optical cart.

  To produce barrel distortion, position the wire mesh close to the first lens and position the large lens about 23 cm from the mesh to focus the image of the mesh on the screen, as shown in the photograph at the left below. The resulting barrel distortion is seen in the left center photograph.

  To produce pincushion distortion, position the wire mesh about 15 cm from the first lens and position the large lens about 23 cm from the mesh to focus the image of the mesh on the screen, as shown in the right center photograph below. The resulting pincushion distortion is seen in the photograph at the right.

  This demonstration also shows "curvature of field," because the focal position of the 23 cm lens is different to focus the center of the mesh than to focus the periphery.

  View from within a few feet to observe chromatic aberration.

• Availability: Available
• References: REFERENCES: (PIRA 6A65.30) See also demonstration L6-41 for another simple setup to produce barrel and pincushion distortion.