I came here via astronomy, where I got used to doing in a New York Minute, ANYTHING to a telescope, no matter how nice the scope nor how trashy the modification, to improve its performance.
With this philosophy in mind, I have vastly improved the IF on my prized 7x50 Fujinon, by harnessing the two eyepieces together in a sort of chain drive. I wrapped a narrow strip of thin, flexible, and springy phosphor bronze alloy over the tops of the eyepieces, and attached it with strips of stretch-resistant and strongly adhesive "kapton" tape. This arrangement allows the binocular to be focused closer by grabbing the left eyepiece and rotating counterclockwise, or farther by rotating the right eyepiece clockwise. The other eyepiece comes along for the ride. The diopter difference is fixed to my personal setting. The metal band comes close to my brow, but just misses.
Although focusing takes a bit of thought, it is worlds more convenient than IF. It is still not quite hummingbird quick, but fast enough for most birding situations. It is better than CF in very cold weather when I wear heavy mittens, because grabbing a knob and turning it is not hampered by the usual restriction of heavy gloves limiting the range and sensitivity of the focusing finger across a central knob. Of course it does not invite twiddling, as focusing the other way necessitates grabbing the opposite barrel with the other hand, so as to twist the opposite eyepiece, not good. But the 7x50 is perhaps the least demanding of all binoculars to focus, and I can hit focus on the first rotation almost every time.
A side complication is that the force on one eyepiece now must be sufficient to turn the other eyepiece as well. In a careless moment, this considerable torque can collapse the IPD setting. So, I had to also install an IPD limiting block between the barrels. I have read that Leupold makes such a thing for their binoculars.
There has been a ray of appreciation of IF Porros here lately for their optical quality, to which I can attest, but the IF itself is invariably seen as the death knell for birding. With this modification, the focusing becomes acceptably easy.
OK, the FMT-SX still weighs 3 pounds and measures about a foot in every direction. But carried on a diagonal strap across one shoulder, it is now a quite tolerable birder for those days when I am under the evil possession of "view quality uber alles".
Closet IF 7x50 fans who implement this improvement can stop thinking of their instruments as good only for astronomy or great distances. And, stop lying to themselves that the depth of field is so great that everything from some absurdly small distance to infinity is sharp. Even a 7x50 deserves accurate focus for sharp, eyestrain free viewing.
Ron
Very interesting Ron, how about some pics?
How long have you had the Fujis set up this way? I'll be curious how you feel about that arrangement after a month or so.
Kevin,
I've had the setup about three months now, and it is still working satisfactorily. After a couple of months, I decided I liked it so much that I did it to my Fujinon 10x50 too. With its shallow depth of field, the 10x50 benefits from the improvement even more than the 7x50. Its transformation from a pure astronomy instrument into a reasonable daytime bino amounts almost to a rebirth.
Another thing I discovered in shakedown was that since the belt drive must be attached to the FMT-SX's screw-off eye cups (the attachment surface must be cylindrical, not conical, for the drive to work neatly) the cups must be screwed down good and tight or focusing closer will loosen the right cup. Not dangerously or plier tight, just a good hand tight, more than enough to keep them from falling off in normal use.
I'll try to do some pictures later.
I didn't actually expect much response to this insanity. Only an astronomer, tugboat captain, or optofile would own these things in the first place. And if you never even get a look, well, you never will get it. Furthermore, the "ATM" attitude is the antithesis of alpha glass snobbery. Both points of view can be internalized only by somebody like me, suffering from optical bipolarity disorder.
Ron