George Stevens had an interest in widescreen as early as 1951.
However, when filming began on July 25, 1951, SHANE would be composed for the standard ratio of 1.37:1.

"Dad's definite preference was to have his films screened the way he shot them and framed them.  He simply accepted the tradeoff to have a bigger screen in the competitive release climate in 1953."

George Stevens Jr to Bob Furmanek - April 19, 2013

For more information on the widescreen
and stereophonic sound boom of 1953,
please visit Widescreen Documentation

George Stevens Jr: A son of Hollywood