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Re: [OM] (OT) Field Glasses recommendations

Subject: Re: [OM] (OT) Field Glasses recommendations
From: Chuck Norcutt <chucknorcutt@xxxxxxxxxxxxxxxx>
Date: Sat, 03 Jan 2015 09:01:51 -0500
Thanks for the tutorial. I never thought of parallax problems as a limiter of close focus operation for binoculars. But it sure makes sense.

Chuck Norcutt


On 1/2/2015 1:58 PM, Moose wrote:
On 1/1/2015 2:47 PM, Bob Whitmire wrote:
Been looking at binocs, and noted these, which have many features Joan
really wants, are neither waterproof nor fog proof. I think that might
be a real disadvantage, even a deal breaker, for the Outer Hebrides.
For that matter, the coast of Maine. <g> No one seems to have any
glasses that focus that close. The best I’ve found are some
brands—waterproof and fog proof—that focus down to five or six feet.
Quite a bit of difference.

You've put your finger on the reasons we have both, and are often
carrying two different kinds.

The problem with really close focus on conventional designs is the
distance between objective lenses.  You would start to get weird
parallax stuff that your eyes can't handle.

It's all trade-offs. Regular porro prism binoculars have wide objective
spacing, and so give good 3D/distance views. But they never focus very
close. Roof prism designs bring the objectives closer together, and thus
often focus closer. But as you say, never closer than six feet or a
little under (partially depending on your eyes.)

Reverse porro designs bring the objectives even closer together, but are
usually used only for compact, relatively inexpensive designs, at least
in part because they start to lose a sense of depth in the view. I have
an old, cheap pair from the old Nature Company, 7x25, and focusing to
somewhere between 4 and 5 ft. I took them as back-ups to Costa Rica.
They proved to be primary in rainforests. My other pair didn't focus
very close, and there were all sorts of interesting things to see in the
"close enough to want to see, but to difficult/dangerous to get closer"
category, especially in a boat in seaside rain forest. :-)
Interestingly, although not sealed, they never clouded up, even in
considerable heat and 100+%* humidity. Maybe it's that they are so cheap
and unsealed?

That's where the Papilio design is unique. It starts with a reverse
porro prism layout. Then, it focuses by moving the the objective lenses
forward to focus closer. As they do so, they also move closer together.
That's the reason for the relatively small objective diameters, 25 mm.
I'm sure it's why the 8.5x model is the same. Undoubtedly the same
'front end' with stronger eyepieces.

As far as I know, no one has managed to fully seal porro prism
binoculars. The Papilios are relatively well designed for water
resistance. The objectives do their fancy dance behind a window of
sealed, flat glass, so the front is impervious. And they are well made,
with no obvious weaknesses, but not fully sealed, let alone nitrogen
purged. We've had no trouble, but never exposed them to anything
seriously challenging. They've been used on coastal Maine, but only in
the fall.

Then again, there's nothing else remotely like them covering the range
between binocular microscopes and regular binoculars. The view of
close-ish things is amazing - first class optics. Carol was carrying
them on our New Year's walk yesterday, and exclaiming as usual about the
beautiful things out of reach off the boardwalk that she could see
close-up and clear. Me? I'm mostly looking through a camera's lens in
macro mode. :-)

Are there others out there whose mileage varies?


If/when we go to Scotland, the Papilios will come along.

B. Vision Moose

* That's when nothing - NOTHING - is ever quite, really, DRY. It gets
pretty darn humid ,uncomfortable for me, in parts of the US, but this is
a whole 'nother level. I know I've mentioned the Nikon electronic film
camera that went insane out in the forest.
--
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