I have a few pairs of porro bins including the Zeiss Oberkochen but I really never noticed much of a 3D effect until the other day when I was looking through my M3 6x30 Nash-Kelvinator. The 3D effect is so pronounced it made my eyes feel funny - not in the way of being uncollimated though. The bins are in excellent shape with bright and very sharp images. Is it the reticule (or reticle?) that is adding to the effect or what?
I have to say, I do like the effect and have a growing interest in porro bins now.
Basically, the 3D effect (stereo perception) increases with retinal offset and as magnification decreases — 6x being rather low in the scheme of things. In part, this is because lower magnification produces greater perceived depth of field. Stereopsis also improves with a larger field of view because more monocular distance cues are included in the scene. I doubt that the presence of a reticule enhances the effect, but it is conceivable if the reticule provides a distance reference. If the reticule can be removed you might try it either way, but personally I find them annoying.
Ed
I know exactly what you mean about the 6x30 Nash-Rambler making your eyes "feel funny". The Fuji 6x30 FMT did the same thing to me.
When I was youngin', back in the pre-digital era, we had a thingie called the Viewmaster, which looked somewhat like binoculars. In the first model, you inserted a rectangular card with double slides, and later they developed a model that used a circular card with slides that acted as sort of like a slide projector carousel.
The Viewmaster slides had an exaggerated 3-D effect that reminded me of the 6x30 Fuji.
Here's an example of one:
http://www.comingsoon.net/nextraima...mastermovie.jpg
Despite the super 3-D effect and very good depth of field, I still had to fiddle with the IF EPs more than I used to when I had my first pair due to deteriorating focus accommodation, so I ended up selling them. I have a shoe with the words "Fuji 6x30" printed on it, and every time I looked through the 8x32 LX and was disappointed with it's 2-D views, I'd take out that shoe and give myself a swift kick. :-)
Brock