  Classical Cepheids remain a cornerstone of the cosmic distance scale, and
thus characterizing the dependence of their light amplitude on metallicity is
important. Period-amplitude diagrams constructed for longer-period classical
Cepheids in IC 1613, NGC 3109, SMC, NGC 6822, LMC, and the Milky Way imply that
very metal-poor Cepheids typically exhibit smaller V-band amplitudes than their
metal-rich counterparts. The results provide an alternate interpretation
relative to arguments for a null and converse metallicity dependence. The
empirical results can be employed to check predictions from theoretical models,
to approximate mean abundances for target populations hosting numerous
long-period Cepheids, and to facilitate the identification of potentially
blended or peculiar objects.
