I will show you the gimic of enlarging the entrance opening from 28mm to 30mm. Futile effort for getting only another 2mm of the opening?? Absolutely No! Just compare the before and after images shown in the last photo.
I have made an experimental optical device that is extremely beneficial for the learner of Optical System. At the same time, I would like to announce the unprecidented Erecting Prism System,”MATSUMOTO-PRISM” that I beleive I have invented.
Amici prism with rhomboid prism on top is not new and used on the recently released APM100/120-90deg. binoculars, as you know.
My idea is quire different from it, despite that 4 relfections are used incluging one Amici.
The shorter the better is the distance between Amici and eye-piece, and the best position of AMICI is just under the eye-piece. The longer distance from eye-piece means the larger AMICI required. In the case of my Prism System, the AMICI locates just next to the eye-piece and gives the enough lateral shift in combination with the mating right angle prism as a unit. The point is that the second group of “2+3″(one right angle prism+Amici; 3 reflections in total) in the position above will not cause any image rotation by the motion of IPD change. In general, any odd number’s reflections system in U-return won’t cause any rotation of the image, just like the even nuber’s reflections system in the same direction won’t cause any image rotation either.
I will tell you just to be sure that I am not shifting from EMS to above mentioned new prism system, but just wanted to suggest my new idea to you, from my accademic interest.
Studying other erecting system will lead to admit the speriority of the EMS in the end.
The IPD is 70mm because of the diameter of the lens. But, because of the extra-large eye-lenses and the excellent off-axis performance, there was no strain even for me of 62mm of the IPD. Your eye performance will be boosted up to twice, as if you became 12-feet of the Giant, that must be a thrilling experience.