  Lippmann (or interferential) photography is the first and only analog
photography method that can capture the full color spectrum of a scene in a
single take. This technique, invented more than a hundred years ago, records
the colors by creating interference patterns inside the photosensitive plate.
Lippmann photography provides a great opportunity to demonstrate several
fundamental concepts in signal processing. Conversely, a signal processing
perspective enables us to shed new light on the technique. In our previous
work, we analyzed the spectra of historical Lippmann plates using our own
mathematical model. In this paper, we provide the derivation of this model and
validate it experimentally. We highlight new behaviors whose explanations were
ignored by physicists to date. In particular, we show that the spectra
generated by Lippmann plates are in fact distorted versions of the original
spectra. We also show that these distortions are influenced by the thickness of
the plate and the reflection coefficient of the reflective medium used in the
capture of the photographs. We verify our model with extensive experiments on
our own Lippmann photographs.
