Skinny and Fat Mirror Images
Why do some mirrors make you look skinny and others
make you look fat? Is this due to slight concave or convex
curvatures of what should be flat surfaces? i.e., dressing room
mirrors that make you look thin or the "fat" mirror in the house
that makes everyone have an extra bulge around the middle?
A completely flat mirror will show an image behind it of exactly the same
shape and size as the actual object. Slight curvature along only one axis
can make a person look fat or skinny. To make you look thin, your image
needs to be compressed horizontally or extended vertically. Most mirrors
bend over time top to bottom. If seen from the side, there is a slight
curvature in the edge. The top and bottom edges are usually straight. Your
home mirror can do this due to its own weight. If the center bulges out a
little bit, your height will appear slightly smaller but your width will not
be changed. This can make a person look a little fat. If the center bends
back a little, then you can look a little taller without looking any wider.
Mirrors can bend along other axes, but the one described is most likely.
Dr. Ken Mellendorf
Illinois Central College
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Update: June 2012