Yes, that is the case for most of the above patents. Thanks, PE.
US 6,518,009 (Mydlarz et al., High intensity exposure photographic imaging method emplying iridium doped high chloride emulsion, Kodak) describes the use of an iridium doped AgBr Lippmann emulsion - to prevent HIRF, I assume.
... wherein the high chloride silver halide emulsion layer is comprised of silver halide emulsion grains containing at least 90 mole percent chloride, based on silver, obtained by providing a high chloride host emulsion, bringing a Lippmann emulsion comprising primarily fine silver bromide grains doped with iridium into contact with said high chloride host emulsion, and subsequently chemically sensitizing the high chloride emulsion.
Yes, this is exactly the case. Iridium in tiny quantities is also added at about 10^6 moles / mole of silver to control reciprocity, and this is why most modern films have better reciprocity than older films. Same goes with paper.
I know Jerzy and am familiar with his work. I am familiar, in general, with the emulsions you have noted in his patent.
I have even seen a formula where a few nano-mol Iridium per mol Silver had been used. That is what I find so intriguing: it reminds me more of homeopathy than that chemistry I had at school.
But this also hints at the cleanliness there has to be at industrial emulsion-making.
Oh, I just found an error in my post above. That is 10^-6 moles of Iridium / mole of silver. Aaaak. Sorry about that error. Thanks for the catch.
I should also have added to that post, now that I see it again, that the Iridium must be made up in a special solution to prevent decomposition, and that addition must be at an optimum time during the run of silver. This time is often determined by trial and error and then running comparative reciprocity tests.
PE
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...,but two layers often act as if they have a huge partially reflective mirror between them.
PE,
Assuming that any reflection issues inbetween layers are due to surface tension, I further assume that coating those layers simultaneously in contrast to coating them in several runs would yield different effects. Actually, I expect simultaneously coated layers of identical gelatines (or rather RI) not to show any interface reflection at all.
AFAIK, coating at one time and coating in multiple passes in a machine causes no change in interlayer reflections or refractions. The effect is not related to surface tension. It is more like placing two sheets of flat glass in contact and you can tell this has been done as you can see it.
In lenses, a similar effect is when the lens components are assembled but require coating on each element to remove these effects. The acutance dye in film serves a similar purpose.
AFAIK, coating at one time and coating in multiple passes in a machine causes no change in interlayer reflections or refractions. The effect is not related to surface tension. It is more like placing two sheets of flat glass in contact and you can tell this has been done as you can see it.
PE
I agree. Each layer being in close contact with the layer on which it has been coated (that is, there is no air interface between them!), you will only get reflections when the refractive index difference from one layer to another becomes large. However, this is highly unlikely if the same kind of gelatin and silver concentrations have been used in all layers.
That was what I tried to hint at. I assume gelatine gets anistropic at/towards the tiny interface with another medium.
The reason for this I only can speculate on. It could be mechanical tension. Though I expect this would not be established in case of wet/wet coating of similar gelatine solutions.
However, even in this case there would be an interface. In the form of a layer of wetting substances.
There is always an interface whether the layers are singly coated or coated in multiples at one time. There are tiny refractive index changes due to the chemicals present in the layers due to the fact that layers differ in content. The difference within the layer itself is substantial.
Think of the lens analogy. You have to coat lenses even though you may use the same glass in every element. It is the interface that counts even if there is no air there.
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