Telescope Reviews: Zeiss Binoculars

Ed, I fear that you have it reversed.
If you have or can get a copy of Mil Handbook 141, Optical Design, read the chapter on design of the complete telescope( including a binocular with prisms in the example he gives), and the eyepiece design section, by Robt. E. Hopkins. He was a prof at the Univ. of Rochester Institute of Optics for many years, wrote much of the cited Mil Handbook, and designed the eyepiece in the WW II wide angle Bausch & Lomb 7 x 50 with 5 element oculars. ( The Kunming suppliers and their importers should make something like that the basis of the 7 x 50, 10.5 x 70, 15 x 85, 20 x 110. Larger prisms and a new basic body would be required. Perhaps Markus Luddes will back this one also. I have the optical drawing and some of the mechanical specifications somewhere, but have not seen it for years. Another copy could be obtained, or could be obtained in the past.) I do not know Hopkins' whereabouts. I last saw him at SPIE a long time ago. His daughter was in a Spanish class with me. He was one of the founders of Tropel, whose products appeared at the forefront of microprocessor lithography.

In Mil Handbook 141 and/or in the Kingslake edited series on Optical Instruments, or elsewhere in his highly respected writings, Hopkins said that eyepiece performance, and the work of the designer, improves with focal length, other things being equal. I may have seen this in Bruce Walker, Warren Smith, Koenig and Koehler, etc. also.
Mil. Handbook 141 was available free for a long time. I have seen it for sale by Deutsche Optik, Surplus Shed(?), and probably elsewhere. I am sure that there is still probably a copy in the library at the Institute of Optics at the Univ. of Rochester, N. Y. It is of course, very dated, but contains much valuable basic information.

I have no explanation for the Tele-Vue examples you give, and cannot comment. Perhaps Al Nagler would . Though fairly widely read in the field, I am not a lens designer, nor have I played more than ten minutes with the free online OSLO program, though would like to play with it or Zemax or others, and become proficient in some optical CAD program , in particular for elaboration and addings graphics to my hp48 mirror virtual roof Amici general inclination angle design program mentioned in the recent Macau 200 mm. binocular thread.
The annual SPIE convention is upcoming. Perhaps some attendee can put this eyepiece focal length vs. performance/design difficulty question to Warren Smith or one of the other experts with experience .