plumb bob for Pülfrich effect
Date1970-1985
Inventory Number2004-1-0234a
ClassificationPlumb Bob
Subject
User
Edwin H. Land
1909 - 1991
Maker
General Hardware Manufacturing Company
1922-present
Cultural Region
Place of Origin
Dimensions16.3 × 4.2 × 4.2 cm (6 7/16 × 1 5/8 × 1 5/8 in.)
blue board box: 7 × 37.5 × 12.4 cm (2 3/4 × 14 3/4 × 4 7/8 in.)
blue board box: 7 × 37.5 × 12.4 cm (2 3/4 × 14 3/4 × 4 7/8 in.)
Material
Accessoriespost chain
DescriptionGilded conical plumb bob with chain used to create the Pülfrich effect. The cone is marked: "S 24 OZ".
In Collection(s)
Signedon collar screw: GENERA HARDWARE / MFG CO. NY, NY
FunctionThe Pülfrich Effect is an optical illusion in which an object which is moving in a plane parallel to the viewer's eyes seems to move out of that plane and to approach (or recede from) the viewer. To cause the illusion, it is necessary only to dim the light reaching one eye by means of a neutral density filter. This illusion is stereoscopic: It occurs only when the moving object is being viewed with both eyes.
The classical demonstration of the Pülfrich Effect is by a swinging pendulum. The pendulum is swung back and forth; when viewed normally with both eyes, the pendulum just seems to swing back and forth. When a filter is placed in front of one eye, the pendulum suddenly seems to be swinging in an ellipse parallel to the floor. The Pülfrich effect is thus a consequence of the fact that at low light levels the brain's response to visual information is slower; by selectively limiting the light level to one eye, the relative delay in image perception creates an illusion of depth.
[This text was taken from the following website. An animated version is found here.]
The classical demonstration of the Pülfrich Effect is by a swinging pendulum. The pendulum is swung back and forth; when viewed normally with both eyes, the pendulum just seems to swing back and forth. When a filter is placed in front of one eye, the pendulum suddenly seems to be swinging in an ellipse parallel to the floor. The Pülfrich effect is thus a consequence of the fact that at low light levels the brain's response to visual information is slower; by selectively limiting the light level to one eye, the relative delay in image perception creates an illusion of depth.
[This text was taken from the following website. An animated version is found here.]
ProvenanceThis object belonged to Edwin H. Land and came from the Rowland Institute, Harvard University. Gift of the Edwin H. Land Family.
Edwin H. Land
Date: 1970-1985
Accessories: post chain
Object number: 2004-1-0234b
W. & L. E. Gurley
Date: circa 1898
Accessories: stored in case with 5236a
Object number: 5236b
Keuffel & Esser Company
Date: circa 1880
Accessories: All six plumb bobs in this series (Inv# 1996-1-0033, -0034, -0035, -0036, -0037, and -0038) are stored in the same small wooden box.
Object number: 1996-1-0033
Buff & Buff Manufacturing Company
Date: 20th-mid 20th Century
Accessories: small black nut; "Buff" plaque; yellow cardboard box
Object number: 1997-1-1837
Buff & Buff Manufacturing Company
Date: circa 1938
Accessories: All six plumb bobs in this series (Inv# 1996-1-0033, -0034, -0035, -0036, -0037, and -0038) are stored in the same small wooden box.
Object number: 1996-1-0034
American
Date: 1880-1940
Accessories: All six plumb bobs in this series (Inv# 1996-1-0033, -0034, -0035, -0036, -0037, and -0038) are stored in the same small wooden box.
Object number: 1996-1-0035
American
Date: 1880-1940
Accessories: All six plumb bobs in this series (Inv# 1996-1-0033, -0034, -0035, -0036, -0037, and -0038) are stored in the same small wooden box.
Object number: 1996-1-0036
American
Date: 1880-1940
Accessories: All six plumb bobs in this series (Inv# 1996-1-0033, -0034, -0035, -0036, -0037, and -0038) are stored in the same small wooden box.
Object number: 1996-1-0037
American
Date: 1880-1940
Accessories: All six plumb bobs in this series (Inv# 1996-1-0033, -0034, -0035, -0036, -0037, and -0038) are stored in the same small wooden box.
Object number: 1996-1-0038
