  Error occurs in data transmission process when some data are missing at the
time of reconstruction. Finding the best dual frame or a dual pair that
minimizes the reconstruction error when erasure occurs,is a deep-rooted problem
in frame theory. The main motivation behind this paper is to characterize the
optimal dual under the spectral and operator norms. Here we give several
equivalent conditions for which the canonical dual is an optimal dual frame for
a given frame. We also go on to characterize the set of dual pairs which
attains the optimal value.
