BirdForum is the net's largest birding community dedicated to wild birds and birding, and is absolutely FREE!

Register for an account to take part in lively discussions in the forum, post your pictures in the gallery and more.

Reply to thread

Message: <blockquote data-quote="John Dracon" data-source="post: 1386174" data-attributes="member: 14799">Henry -  The worst binocular with overlap issues I have found was the discontinued B&L 10x40.  As we all know, the offset of the objectives and oculars in porros is a function of prism construction.  And the inherent gain is a significantly shortened instrument.  Those clever Germans designed the roof prisms to keep the binoculars reasonably short yet slim.  Roofs undoubtedly have an inherent advantage when it comes to very close range.  But is it because their objectives are closer together?But overlap is inherent in all binoculars, porro or roof.  Even those so-called reverse porros display as much overlap as the traditional ones, which intuitively shouldn't happen since the objectives are so close together.  But I would suggest that other variables come into play when discussing overlap, variables that I don't fully understand.Certainly power and field can play a role.  We all differ in our interpupilary distances and ability to converge.  The quality of the optical system off axis may be a huge when it allows us to handle overlap without being overtly conscious of it.  Don't know.When I look through my Zeiss 8x32 Fl at close focus (around six feet) the overlap is pronounced.  But it doesn't annoy me.  Moved outside on a rock solid mount, the same binoculars show overlap at five miles.  I don't know if the Zeiss barrels are parallel or with a slight toe in.  But even if we look at what we call infinity in most binoculars, slight overlap is present.I know we all chuckle at the movies when our hero peers through his binocular and the perfect circle doesn't occur.  It doesn't occur with us too  We just aren't aware of the overlap since none of us can focus on the entire field at the same time with both eyes.Just as the Navy found through its experiments that the average person could handle 7 power binoculars better than higher powers, perhaps there is what I would unscientifically call the overlap factor or quotient which causes annoyance with the viewer.  It may be inherent in individual binocular models or the individual itself. I know you are far more analytical than I about optical matters.  Is overlap that big a deal?   What are the true variables that make overlap so annoying to binocular users? If reverse porros show the same overlap as traditional porros, and they do, what are the optical issues involved.John</blockquote>

Verification