Elasticity of subsitution: a redundant calculation? Elasticity of subsitution is a measure of the curvature of an isoquant1 and can provide us information regarding the nature of the production functions we are dealing with. this is visualized in Advanced Microeconomic Theory 
by Geoffrey A. Jehle (Author), Philip J. Reny  (page 130 in the book) as:



However I wonder, isn't this information regarding the curvature of a isoquant given by the production function? what novel information does the calculation of elasticity of substitution provide us with? 



1. I'm aware that elasticity of substitution can also be applied to consumer theory, just that its dominant in producer theory.
Why would one need to graph the function? Isn't any information in the graph already given in the function?

In  a certain sense all calculations are redundant as they are mathematical tautologies. Yet these indices make some things more clear, which is obviously useful.