Lippmann Photography and pinhole cameras
Posted: Sat Apr 25, 2009 3:44 am
I am trying to make Lippmann photographs using PFG-03M holographic film plates and a .8 mm aperture 32.2 cm focal length pinhole camera, without mercury.
First, I have a conceptual question that I have been unable to answer even after reading many lippmann papers. When mercury is used as a reflector,it makes sense that the "normal" photo process would not occurr, whereby light passing through the emulsion creates a sort of column of opaque silver; since almost all light is reflected back, only light that creates a standing wave with itself upon reflection will be strong enough to interact with the emulsion, so instead of a column of silver, layers of silver at half-wavelengths are formed. However, when using a gelatin-air interface as the reflector, it seems to me that the relfection is so weak that the majority of light would interact with the emulsion in the same way that it would in a normal black-and-white photograph, passing straight through and leaving a trail of silver seperated from the silver-halide or whatever. Certainly some laminae would occur, but wouldnt they be overpowered by the non-interference effects?
My second question is procedural. I have no idea what kind of exposure lengths I should use. I have read that, especially without mercury, very long exposures are needed, so I have tried, so far, 30 and 40 minute exposures to a still life illuminated both by diffuse florescent lights and an incandescent light, but without any success. What prompted the first question is that when I develope the film, I don't see any opacity at all. I expected to get a black and white negative or something, at least. Clearly, I don't understand whats going on! Anyway, do holographic plates have a property similar to speed in normal film that would infform, along with the amount of light and F-number, the exposure time?
Any help would be much appreciated. If these questions are answered elswhere, please feel free to refer me to a paper or another post or something.
First, I have a conceptual question that I have been unable to answer even after reading many lippmann papers. When mercury is used as a reflector,it makes sense that the "normal" photo process would not occurr, whereby light passing through the emulsion creates a sort of column of opaque silver; since almost all light is reflected back, only light that creates a standing wave with itself upon reflection will be strong enough to interact with the emulsion, so instead of a column of silver, layers of silver at half-wavelengths are formed. However, when using a gelatin-air interface as the reflector, it seems to me that the relfection is so weak that the majority of light would interact with the emulsion in the same way that it would in a normal black-and-white photograph, passing straight through and leaving a trail of silver seperated from the silver-halide or whatever. Certainly some laminae would occur, but wouldnt they be overpowered by the non-interference effects?
My second question is procedural. I have no idea what kind of exposure lengths I should use. I have read that, especially without mercury, very long exposures are needed, so I have tried, so far, 30 and 40 minute exposures to a still life illuminated both by diffuse florescent lights and an incandescent light, but without any success. What prompted the first question is that when I develope the film, I don't see any opacity at all. I expected to get a black and white negative or something, at least. Clearly, I don't understand whats going on! Anyway, do holographic plates have a property similar to speed in normal film that would infform, along with the amount of light and F-number, the exposure time?
Any help would be much appreciated. If these questions are answered elswhere, please feel free to refer me to a paper or another post or something.