Quote Originally Posted by Struan Gray View Post
Both emphasise that the best and most colourful view is to be had by illuminating with collimated light and viewing in conditions which minimise diffusion, both of the illuminant, and of the light scattered by the picture. I had been led astray by modern references which assert that Lippmann plates can be, or even should be, viewed with diffuse light. Ives and Wall make much more sense for viewing colours formed by diffraction fringes.
No way, common wisdom (and experience) still holds: you do need diffuse light for viewing a Lippmann photo. I've never done any "photos of the spectrum" though. I assume they may be different, getting even closer to a hologram.
But a Lippmann photo of what they used to call, natural objects, absolutely requires diffuse light for reconstruction.

Quote Originally Posted by Struan Gray View Post
With incoherent monochromatic light the fringes are few and weak, and overlaying fringes from a whole spectrum only makes the matter worse. In a perfect world there is no reason why a pattern of silver grains in gelatin could not cope with recording a whole spectrum diffractogram, but with conventional photochemistry and the small depth of the inteference structures, there is too much mixing of the colours and you lose too much saturation.
Definitely no easy task. But obviously, it can be done. The finest Lippmann photographs by Lippmann, the Lumière brothers, Neuhauss, Cajal and maybe others clearly demonstrate that large bandwidth spectras can be recorded into a AgX emulsion. Some of these photos are of outstanding quality and pretty bright.
By the way, I suspect that Ives' emulsions may simply not have been good enough in respect to grain size/resolution.