Joe wrote:The question arises: has anyone tried to measure the CRI of a Lippmann photograph? We may think that a Lippmann phograph has a very good CRI, but is this really the case?
I am not aware of any paper about this.
The only thing that comes to my mind is Jean-Marc Fournier's work. He examined the spectra recorded by Lippmann photographs. In “An investigation on Lippmann photographs: materials, processes, and color rendition” (SPIE 2176, pp. 144-152),
he writes:
The most puzzling aspect of Lippmann photographs is their ability to reconstruct accurately a given spectrum, whatever the position or width of the light distribution.
Referring to a section of a photo by Lippmann, he points out:
These spectra are broad! the direct correspondence of these spectra with the real spectra of similar scenes measured with the same modern instrumentation is striking. Most notably, these spectra absolutely do not resemble the kind of sine function that would result from the diffraction by a volume grating.
Comparing holography and Lippmann photography, he says:
...when volume color holograms are recorded on one or two panchromatic materials, each part of the hologram carries information on the whole scene, and therefore, each very narrow band of coherent light used at the recording stage creates a set of well-contrasted sinusoidal fringes in the entire interference area. The resulting pattern is the superposition of three (or four) sets of fringes which have a contrast sufficient to imprint them deeply into the emulsion. This implies two consequences: the first, that an emulsion for recording a wide spectrum in Lippmann photography must be very thin (on the order of one micron), so as to avoid diffusion by scatterers carrying no information on wavelength; the second, that at the reconstruction stage, a Lippmann photograph can, in principle, restore a spectrum very close to the copied one, whereas the spectral distribution of the reconstruction of a color volume hologram can be described by the superposition of three (or four) sine functions, making it in some way alike that of a trichrome (additive or subtractive) color photograph.