A very high speed film formula

[Photo Engineer]

I have posted the patent number of several of these. I believe that one author is Ken Reed. Not sure, but he is the author of one patent # I posted here.

PE

[Kirk Keyes]

OK - here's one from Ciba-Geigy in the 70s that looks like it follows much of this process: 4184877.

[Photo Engineer]

Kirk;

In patent 4184877, the difference is that Ammonium Halides are used, and the Iodide is not ramped down. And so, the result is not a graded core shell, but rather an abrupt core shell. At least I assume that, as the Bromide was added after the Ammonia digest was completed. And, contrary to my example, the core is a mixed Br/I not pure I. This seems to be what they are saying.

I didn't look at the figures, but I assume they are rather thick grains. IDK. It is old. More modern T-grains are thinner I would think and not use ISO washing as is noted in the patent. The emulsion is not very monodisperse at 20% variance, but I'm not sure how they used it and again, I didn't look at the figures.

PE