Quick test for dipvergence (1 Viewer)

Not noted for their technical tips the folks at birdwatching.com posted this quick check for dipvergence (convergence in the vertical plane) by viewing a horizontal wire with the bins a little way from the eyes. The wire should "line up" between both tubes.

http://www.birdwatching.com/optics/education/alignment.html

Seems to work too. One of my old Nighthawks is out of sorts according to this. Everything else seems fine.

Kevin - I know that what you have stated about dipvergence is accurate, but for a few people it isn't. Allow me to explain. For whatever reason, binoculars which are in perfect colimation, to my eyes, never show the horizontal line to be on the same plane. One barrel, the right one, is consistent in showing the line to be lower. I discovered when hand colimating that making the lines coincide actually introduced a serious error in colimation for people with normal eyes. My opthamologist told me that my brain "sees" differently than most people, even when the binoculars are in colimation. Strange as it seems, it is true for me. John

Very interesting, John. I'd never heard of that.

So the "center point" of your visual field doesn't coincide

You don't have a veertical squint (or whatever the vertical equivalent would be ... a dipint(?)) do you?

Do you glasses correct for this (I presume you wear them) with a vertical prism or is all the correction you need now built into your visual system?

Do you find "normally" converged bins are dipvergent for you?

Curiously yours!

John Dracon said:

For whatever reason, binoculars which are in perfect colimation, to my eyes, never show the horizontal line to be on the same plane. One barrel, the right one, is consistent in showing the line to be lower. John

Click to expand...

That is exactly what I experience in binoculars since I've been familiar with this little test. The only binocular in perfect alignment - straight line in both tubes during the test - was the Zeiss 7x42 FL. Still, I struggled to get that wellknown relaxed viewing that others experience and are so enthusiastic about. Cheap Chinese porro's gave me a more satisfying view, and these showed of course the same lower line in the right barrel during the test.

It must be my eyes; just tested my Minox 8x32 BL's - the line is lower in the right barrel. When I use them upside-down, like I do when wearing a cap, I can focus with my thumb. The view is significantly more relaxed than when I'm using them in the "right" manner ( focus wheel up, focusing with index finger ). Still, when I do the test with the bins upside-down: the line is lower in the right barrel.

Bought a Canon 10x30 IS today. Guess what? The same broken line during the test, lower in the right barrel. To my eyes, they seem very relaxed when viewing through them, especially of course with the IS button pressed.

I sold my Zeiss 7x42 FL's to a birding mate, who uses them all the time and claims they are far better than his old Leica Trinovid 8x42 BN's. I'm glad I could make him happy, but perfectly aligned bins are no guarantee I can see what others see.
It's a strange thing, though. I have learned to live with it. Positive point is, I never have to buy alpha again for this reason.
More beer!! B

Regards,

Ronald

I can't do that test. When I pull the bins away from my eyes I only see through the left lens—because of the extreme dominance of my left eye, I presume. Instead I do it by opening the bins well past the point where the images converge. I assume that works as well?

Michael

I have a problem similar to John's. When I do the telephone wire test, even with binoculars freshly aligned by the factory I see about a 5° dip on one side. It doesn't seem to affect my use though - at least no headaches.

Kevin - I don't know enough about binocular vision to discuss intelligently what I see. Things just don't line up with me. Now I have astigmatism which is corrected in my trifocals and actually possess what is close to 20/15 vision corrected. But holding the binoculars at arms length to see the two circles separated may have something to do with it, and as my eyes move closer. things simply converge, and I have no problem seeing with binoculars. Others have commented on what I experience, so it must be something which is being introduced in the process of checking for horizontal lines. John.