Toby, I posted this thread because of the original design concept for the 1.2-1.4 prototype: to add a convex element to a standard lens. This reflects their efficient and effective way to design lenses during the time when it took much longer and difficult to design even simple optics. At around the same time, the same designs seemed to be shared with minimal tweaks (like the distance between the front and the rear groups) between LF and EL-Nikkors.
Hi Akira, I got that, but that prototype cannot be too closely related to the 55mm CRT Nikkor for one very good reason: the CRT is deliberately designed with negative field curvature, as are almost all Oscillo lenses (Wollensak, Elgeet, Ilex that I know of) in order to hold all parts of a curved CRT tube in focus at a optimized distance. The general optical design might be similar (anyway, all are some variation of a double gauss design), but the element curvatures are nowhere near standard flat-field lenses. This, of course, gives them the unique out-of-focus look that won't be duplicated by adding a diopter at the front. Just for fun, here are a few pics from an Elgeet STL-Navitar 86mm f1.2, which is a symmetrical double gauss design that says "Specially made for TRW Space Technology Laboratories" It has at least two thoriated elements and is highly radioactive. It has the most wild field curvature of any lens I have ever used (optimized for 1:1) and is, I believe, as sharp or nearly as sharp as the Nikkor-O. It is difficult to use, as the effect is over the top, but occasionally I get a shot I like. Again, that field curvature is what produces the "distorted bubbles" in the bokeh, somewhat similar to what happens in the Nikkor-O in a more limited way, and also in lenses like the Wollensak 75mm f1.9 Oscillo-Raptar, another enormously fun lens in two versions, one optimized for 1:0.5 and one for 1:0.9
Of these, the last two show the same image shot first at f1.2 and then at f4, where the effect becomes a bit more manageable.
