  We study the holographic D3/D7 setup dual to N=4 supersymmetric Yang-Mills
with quenched fundamental matter. We extend the previous analyses of
conductivity and photoproduction to the case where there is a finite electric
field. Due to the electric field a special region in the D7-brane geometry,
labelled the singular shell, appears generically, and the computation of
correlators involves a careful study of the indicial exponents both at this
singular region and at the horizon. We show that there is a unique choice
consistent with the known expression for the electrical conductivity found by
Karch and O'Bannon. We explore the parameter space spanned by the quark mass,
the baryon density and the electric field. We find a region where the
conductivity and photoproduction change rapidly and trace this behavior to
competing effects which manifest themselves as a crossover behavior in the
probe brane embeddings.

High Energy Physics - Theory