The ab-plane infrared and visible (3 meV–3 eV) response of Bi 2Sr 2CaCu 2O 8+ δ (Bi-2212) thin films has been measured between 300 and 10 K for different doping levels. In the superconducting state, dramatic differences appear between the underdoped and optimally/overdoped regimes regarding the electrodynamics of the formation of the superfluid condensate. In the optimally doped and overdoped regimes, the superfluid grows up by removing states from energies below 60 meV. This energy is of the order of a few times the superconducting gap. In this respect, optimally doped and overdoped Bi-2212 exhibit a conventional behavior. In the underdoped regime, states extending up to 2 eV, far beyond any conventional scale for a BCS-like mechanism, contribute to the superfluid. The spectral weight change, below the critical temperature and beyond the intraband transitions, may be assigned to a change of electronic kinetic energy ∼1 meV, a figure which addresses the issue of a kinetic energy driven mechanism.