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Re: [OM] Olympus Binocs

Subject: Re: [OM] Olympus Binocs
From: Kenneth Sloan <sloan@xxxxxxxxxxx>
Date: Fri, 2 Apr 1999 12:59:11 -0600
OK, I'll play.  I picked up a pair of Olympus 9x20 PC (??) (Field
5.5deg) binoculars when they snuck through my "Olympus" search filter on
eBay.


> ... The criteria I use for testing binocs are, after 
> finding a suitably bright surrounding: 1) hold the binocs at arm's length 
> and look at/through the eyepieces. Do you see a "square within a
> circle"? 

Nope - a circle

> Is there a shadow-like attenuation in the shape of a square or diamond, 
> imposing on the edges of the circle of light? If so, not good. If just a 
> round circle, then good.

Ah...good!

>    2) Let light stream through the objectives and 
> place a card near the eyepieces. How large a circle of light is projected 
> onto the card? 

2.2222222222222...mm did I get it right?

>  Big = good for brightness, up to 7mm, after which bigger 
> is not better. (This is actually controlled by magnification and 
> objective size, and a 7x50 binoc should give a 7mm diameter "exit pupil." 
> 3) Look through the binoculars backward. Are there obstructions in the 
> lightway?

Barely noticable, miniscule "chord" shaving off a tad...

>  A "flattened circle"? (While you're there, look for prism chips 
> on used binocs.) I look for minimal or no circle flattening. 4) Looking 
> through the binocs the correct way again, how far away from my eyes can I 
> hold the binoculars and still get a full field of view? (Eye relief). 

With the rubber thingies extended...they touch my eyebrow.  The more
important test - roll back the rubber thingies and use with eyeglasses -
no joy.  the field of view is markedly reduced.  But then, I've never
owned a set of binocs that give a full field of view with eyeglasses.

> Typically, quality binoculars offer longish eye relief (but not always). 
> Cheapo binoculars, on the other hand, almost ALWAYS require pressing your 
> eyeballs up against the eyepieces. 5) The last test is the most rigorous: 
> on a clear night, gaze at a starfield. 

I'm sorry - it's just past noon...the only star in the sky looks the
same everywhere in the field of view (and ooooh - that hurst my eyes)

> them are roof-prism designs (straight barrel) and, honestly, the porro 
> prism design (bent barrel) has the optical edge.

I always get confused.  In the good old days, binocs were binocs.  The
narrown end had little lenses and the wide end had big lenses.  Lood
through the little lenses at the narrow end and point the big lenses at
the target.  The target looks bigger!  Now, we have binocs with same
size lenses at each end, and straignt barrels.  Sometimes the taget
looks bigger and sometimes it looks smaller; it takes me 1.3 tries (on
average) to get it right).  The Olympus 9x20 PC (what does that PC mean,
anyway?) is this new-fangled design where you look through the wide end
and point the NARROW end at the target (doesn't this make the
rangefinder base tiny? What does this do to my stereo imaging?)

> ... "Do I like how these binoculars make me feel?" Let me know what 
> happens. --Kelton

Actually, that's what I like best about these.  They are weightless.  I
use them at sporting events (hockey, basketball, and soccer) where there
is plenty of light (so the small exit pupil is not a problem) and where
my primary goal is to get as close as possible - but relatively
infrequently (I'm not watching the whole game through them).  I usually
also have a camera bag, a camera body on a monopod, etc.  so I often
just stuff the binocs in a coat pocket, where I often forget that they
are there.  If I wanted to look at stars, or for ships at sea, I would
probably find these inadequate.  Nice opera glasses, though!

-- 
Kenneth Sloan                                            sloan@xxxxxxx
Computer and Information Sciences                       (205) 934-2213
University of Alabama at Birmingham                 FAX (205) 934-5473
Birmingham, AL 35294-1170   http://www.cis.uab.edu/info/faculty/sloan/

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