Date: 3/20/17 6:38 pm
From: Steve Long <steve.long4...>
Subject: Re: [MDBirding] Re: Binoculars, Good selection of 12x
The down side of 12x25 is that they are NOT bright. As the light diminishes
in the evening, I lose the ability to see through them well before losing
the ability to see without them. But, they are plenty bright for daytime
use.

But, the down side of things that are bright is that they are either large
and heavy or have low magnification so as to be small. That is just the
physics of magnification. There are some ways to physically optimize, at
some expense, but really small, bright and powerful is not going to happen
UNLESS we use electronics to capture, enlarge, and brighten an image taken
with a small lens on a very small sensor. But, I have not heard of that
being done for birding binoculars. When it is, I suppose it will also
include image stabilization. Digital cameras can do all that to some
degree, now.

But, at some point in the spectrum of increasing magnification, it becomes
very difficult to AIM the limited field of view accurately enough to include
the intended subject. I am about at my personal limit for that at 12x,
AFTER some practice.

Don't misunderstand; I have larger binoculars and a 20-60x scope. I use the
12x25s for walking around and spotting things when I am not interested in or
able to carry something larger. My comment here was mainly related to the
"jumpiness" not really seeming like much of an issue with the 12x25s that we
use.

I have more problems with "jumpiness" when on my boat and trying to use my
7x50s to see a bird. The boat motion makes the image jumpy, and the low
magnification makes it hard to see detail at a glance. In bright light, I
can sometimes read a buoy number better with the 12x25s than with the 7x50s.
But, I can SEE the buoy with the 7x50s even when it is hard to spot it with
the unaided eye in the dusk. (White bird poop on buoys often makes it hard
to read white numbers on buoys.)

Steve Long
Oxford

----- Original Message -----
From: "Warblerick" <ricksussman1955...>
To: "Maryland & DC Birding" <mdbirding...>
Sent: Monday, March 20, 2017 8:06 PM
Subject: Re: [MDBirding] Re: Binoculars, Good selection of 12x


12x25? Wow, I've never heard of anyone using that for birding. The image
can't be very bright. The exit pupil on 12x25's is about 2mm, or roughly
half what your open pupil is (4-5 mm for most adults in regular light). So
you're only getting about half the available light. Most recommended birding
binoculars have numbers like 7x35 or 8x40, with an exit pupil of 5, which
just about matches your own pupil, allowing all the light coming through the
eyepiece to be used, giving a nice bright image. 12x25 must be like looking
through a keyhole, I would think.

Rick Sussman
Woodbine, MD

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