The optical conductivity of ferromagnetic Fe was calculated with an interpolation scheme fit to first-principles energy bands for paramagnetic Fe with a constant exchange splitting. Most of the contributions to the conductivity originate in the minority-spin bands, making the rigid splitting a valid assumption. The inclusion of electric-dipole matrix elements is essential for obtaining agreement with experiment. The locations of the transitions in the band structure were found by plotting contributions from differential volumes throughout the irreducible wedge of the Brillouin zone, including dipole matrix elements. The strong transitions around 2.5 eV occur between flat bands in large regions of the zone, regions not associated with symmetry points, lines, or planes. The transitions near 6 eV originate in a smaller volume of k space near a symmetry line, associated with an interband critical point.