IF improvement (1 Viewer)

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

On it's face it does seem a little nutty Ron but I try to keep an open mind so I'll hang with you

I look forward to seeing pics and BTW I've had some thoughts along these lines myself. My vision is that of two split rings (one for each ocular) with posts attached (maybe 1 - 1 1/2" long) and a connecting rod to the end of the posts via a pivot. This would form a solid linkage between the two EPs. The extreme right range of motion would be infinity focus and all the way left would be as near focus as would be allowable with the linkage.

Some spit-balling shows me that the near focus would be plenty with a 16x70 FMT-SX and I don't know but could guess that the 7x50 are similar. The same set up looks adequate for the 6x30 AR-SX for most use. Of course I'm not really too interested in doing something like this with the big bins but I can see it on the small ones. Making the IPD fixed wouldn't be mandatory with this either as the center to center distance of the pivots would be the same as your IPD and when that is correctly set the geometry of the linkage would also be correct.

Astronomers do tend to be do it yourselfers :t:

Here's a quick sketch of what I mean...

Here are a couple of pictures of the treatment on the 10x50. The metal strip has been covered with black tape to look a little nicer. The first shows the drive. The second shows how I modified the rainguard, using it upside down, and putting slits in it to accomodate the drive belt. Horrors!
Ron

That looks interesting Ron. I'm gonna mull over this issue a bit more. I would love something simple and elegant in design. You've undoubtedly fallen under the spell of big Fujinons. :eek!:

That's very ingenious, Ron.
I think I could almost dispense with my scope for an SF (synchronised focus) Fujinon 16x70 FMTSX.
BTW, the H stands for Heath Robinson, right? ;-)

John

Ron - I had a pair of those big honkers. Optically, they were outstanding. A friend talked me out of them. Heavy enough to beat a grizzly bear to death. But that heft sure steadys the hand. Seven power binoculars are very underrated. Would your system work with a Fujinon 6x30 IF? John

Ron,

I'm not clear on how the band is attached to the EPs. And...just what is that material? Where does one get it? And... after having it awhile, is there another material you think would work as well or better?

I did a little experiment using some light para-cord on my 6x30s and it linked the two EPs pretty well. On the 6x30 AR-SX the eyecups don't unscrew like FMTs so I'm trying to imagine a way of fixing a band or cord without it looking like hillbilly engineering.

John,
Thank you. I feel sure Leonardo da Vinci would have beat me to this, if only he'd had the same problem.

Kevin and John,
It would work on any IF, provided there is a section of rotating eyepiece that is strictly cylindrical, or straight-barreled, not conical or tapered. And, providing the positiion of that attachment section, combined with the eye relief, gave the adjusting band necessary brow clearance.

I used scraps of stuff I found in the old rocket science workplace, but I think a trip to the hardware store would do it. For the metal band, you need something thin, flexible, and springy. A sheet of material will give an impression of stiffness that will be lost when you cut a narrow strip out. Even a very thin strip would provide the needed tension for the mechanism, but might be so flimsy that the inevitable sideways bump could bend it out of shape. Something around .005" stainless steel, for example. The adhesive tape that secures the metal strip in place, cut to the same width as the metal, should be as stretch-free as possible, and the adhesive needs to be strong, but not in a thick gooey layer like Duct Tape. I think common clear "packing tape" would work pretty well. Then, once you're satisfied with functionality, an overwrap of black electrical tape gives that professional look.

My IF eyepieces do get a hair sticky if they just set thar fer too long, so I give um jist a easy turn, one at a time, to git er a goin smooth agin fore I takes her out. (spits.)
Ron

This is sort of interesting. I have a Leupold Gold Ring 9x35 IF porro, I'm going to tinker with a little. Thanks for the tip.