We discuss the role of Configuration Interaction (CI) and the influence of the number of
configurations taken into account in the calculations of nickel and iron spectral
opacities provided by the OPAC international collaboration, including statistical
approaches (SCO, CASSANDRA, STA), detailed accounting (OPAS, LEDCOP, OP, HULLAC-v9) or
hybrid method (SCO-RCG). Opacity calculations are presented for a temperature T of 27.3 eV
and a density of 3.4 mg/cm3, conditions relevant for pulsating stellar
envelopes.