  There is a conformal equivalence between power law $f(R)$ theories and scalar
field theories in which the scalar degree of freedom evolves under the action
of an exponential potential function. In the scalar field representation there
is a strong coupling of the scalar field with the matter sector due to the
conformal transformation. We use chameleon mechanism to implement constraints
on the potential function of the scalar field in order that the resulting model
be in accord with Solar System experiments. Investigation of these constraints
reveals that there may be no possibility to distinguish between a power law
$f(R)$ function and the usual Einstein-Hilbert Lagrangian density.
