A sample of 65 classical cepheids with P<9d and complete light curves from four-color and Hβ photometry are discussed in connection with their reddening, metallicity, and luminosity. The reddening, derived from Hβ is in excellent agreement with the mean results from all previous investigations. The metallicity spread is small, possibly ranging from about [Fe/H]∼+0.25 to -0.16. The reddening free index [M1], which reflects the metallicity, is also very sensitive to luminosity and, in cepheids, the luminosity dependence dominates. The blue light amplitudes, δB, when converted to FB, the amplitude defect, map the location of the cepheid in the instability strip, not in the temperature coordinate but as a function of the luminosity displacement from the center line PL relation. At a given period the more luminous variables have the largest light amplitude. The PLA relation is Mv= -2.90 log P - 1.4OFB-0.24 and, although derived from the short-period cepheids, it is found to extend to periods of at least 25d without a detectable change in slope.