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[OM] Re: OT..but Optical

Subject: [OM] Re: OT..but Optical
From: "James N. McBride" <jnmcbr@xxxxxxx>
Date: Wed, 18 Jan 2006 18:59:06 -0700
I have a pair of Zeiss 10x56 Nightowls. They are the best I have ever had in
that magnification range but they are heavy. I've been told that they are
better than the current version of 10x56 but have not compared so cannot
verify that. I also have a pair of 16x70 Fujinons that I really like. They
cannot be hand held though. I tend to trust reviews by birdwatchers as they
are very critical when it comes to sharpness. People I hunt with use Zeiss,
Swarovski, and Leica and they all seem satisfied. My son's Swarovski ELs
fell apart internally and had to be repaired. They have been fine since. The
usual advice applies, buy them all and sell the ones you reject. /jmac

-----Original Message-----
From: olympus-owner@xxxxxxxxxx [mailto:olympus-owner@xxxxxxxxxx]On
Behalf Of Chuck Norcutt
Sent: Wednesday, January 18, 2006 4:11 PM
To: olympus@xxxxxxxxxx
Subject: [OM] Re: OT..but Optical


I can't tell you about these two particular models other than offer some
observations on magnification which you may already know.

The Zeiss Victory is quoted as having better twilight performance
because is has lower magnification using the same 40mm objective.  The
exit pupil (objective diameter / magnification) for this 8X binocular is
5mm which is somewhere near the size of your pupil in twilight and will
be brighter than the Dialyt which, at 10X has a 4mm exit pupil.

In additon to being brighter in the low light of early morning and late
afternoon (when birds are active) the 8X glass will be easier to hand
hold without a monopod or other support.  8X is already about the limit
for unaided hand holding and I think 10X is getting pretty shaky.  The
8X glass is also lighter which can make a difference if you're carrying
them around all day.

Human pupil sizes ranges from about 3mm in full daylight to about 7mm
when dark adapted at night.  7x50 binoculars are called "night glasses"
since they have a 7mm exit pupil which is just the right size to fit
through the dark adapted pupil.  Any of these binoculars, however, waste
a certain amount of light during the day since the exit pupil is larger
than can fit into the 3mm pupil of your eye.  For daylight use a 7x50 is
no brighter than a 7x21 since the emerging light beam from the 7x50 (the
exit pupil) can't fit into your 3mm eye opening.

I have 8x40 and 7x35 binoculars.  Both are the same relative brightness
since both have a 5mm exit pupil.  However, I take the 7x35's most of
the time since they are lighter.

The answer is, of course:  It depends.

Chuck Norcutt

JOHN DUGGAN wrote:
<< snip



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