Novice question regarding binoculars
Pete
What does the numbers 7x50 or 10x50 or 8x60 mean with binoculars?
Please explain in non-technical form with simple terms.
Thanks for any help.
--
Pete
newm...@ihug.co.nz
Leonard Migliore
In article <01bc93c7$b379a500$a8efd4cf@newmannz>, "Pete"
<newm...@ihug.co.nz> wrote:
> What does the numbers 7x50 or 10x50 or 8x60 mean with binoculars?
>
> Please explain in non-technical form with simple terms.
The first number (7 in 7X50) is the magnification. A 7X binocular makes
objects seem 7 times closer. Note that, while you may think that 10 times
magnification is better than 7, for many people (like me) the higher power
accentuates shaking, so it's not as pleasant to look through.
The second number (50 in 7X50) is the diameter of the binocular's
objective lens in millimeters. The objective is the lens that you point at
the object you're trying to see. Bigger objectives gather more light, so a
7X50 binocular shows you more in dim light than a 7X35.
--
Leonard Migliore
Laser Kinetics, Inc.
Harvey N Rutt
> > What does the numbers 7x50 or 10x50 or 8x60 mean with binoculars?
> >
> > Please explain in non-technical form with simple terms.
>
> The first number (7 in 7X50) is the magnification. A 7X binocular makes
> objects seem 7 times closer. Note that, while you may think that 10 times
> magnification is better than 7, for many people (like me) the higher power
> accentuates shaking, so it's not as pleasant to look through.
>
> The second number (50 in 7X50) is the diameter of the binocular's
> objective lens in millimeters. The objective is the lens that you point at
> the object you're trying to see. Bigger objectives gather more light, so a
> 7X50 binocular shows you more in dim light than a 7X35.
To the above excellent & succinct reply let me add a couple of points as
a user.
What you choose depends on the use you have for them. 8*30 is a good
general purpose, reasonable size, easy to hold pair. For birdwatching
etc you might want 10* mag, but above 10* most people cannot hand hold
them; you need a tripod, or to rest them on something at least - made
worse as they are heavier. If you will be on an unstable 'platform' (eg
a boat) go for 7* mag.
The second number has a *big* effect on size, weight & cost; *30 are
much smaller, lighter, cheaper than *50, but in dim light (dusk & dawn)
noticeavly brighter; in good light you wont notice the difference. I've
switched to 8*40 from 8*50 for birdwatching.
There is *absolutely no point* in having the ratio of the two numbers
(ie 8*30 about 4mm, 7*50 about 7mm) greater than ~7mm, because that is
the size of the pupil of the eye wide open; you do see daft adverts for
binocs with silly ratios.
Two other important factors - get ones with good coatings, multiple
reflections can mess up the image, especially looking towards (NOT AT!)
the sun; 'eye relief' is *very* important if you wear specs.
Other than that you pretty much get what you pay for in optical quality!
Harvey Rutt
John Wasser
Pete wrote:
>
> What does the numbers 7x50 or 10x50 or 8x60 mean with binoculars?
Magnification X Diameter of the front lens (mm)
The larger the front lens, the brighter the image and the
finer the detail you can see. However if the diameter is
much larger than 7 times the magnification (7X49, 5X35)
then some of the light gathered will not make it into the
eye and will, therefore, be wasted.
If you are looking at something bright (like a daytime
scene or the moon) then a lot of the light gathered
(at 7 times the magnification) will be wasted because
your eye pupil is not wide open. For daylight use, 5
times the magnification (7x35, 10x50) is lighter to
cary and just as effective.
Joerg Angerstein
Leonard Migliore wrote:
> In article <01bc93c7$b379a500$a8efd4cf@newmannz>, "Pete"
> <newm...@ihug.co.nz> wrote:
>
> > What does the numbers 7x50 or 10x50 or 8x60 mean with binoculars?
> >
> > Please explain in non-technical form with simple terms.
>
> The first number (7 in 7X50) is the magnification. A 7X binocular
> makes
> objects seem 7 times closer. Note that, while you may think that 10
> times
> magnification is better than 7, for many people (like me) the higher
> power
> accentuates shaking, so it's not as pleasant to look through.
>
> The second number (50 in 7X50) is the diameter of the binocular's
> objective lens in millimeters. The objective is the lens that you
> point at
> the object you're trying to see. Bigger objectives gather more light,
> so a
> 7X50 binocular shows you more in dim light than a 7X35.
>
> --
> Leonard Migliore
> Laser Kinetics, Inc.
The exit pupil is the ratio of lens diameter and magnification. In
case of 7x35 it is 5 mm, in case of 7x50 it is more than 7 mm. The dark
adapted eye of a child can be as large as 8mm, adult have decreasing
pupil diameter and at an age of 50 normally not more than 5mm. The
result would be that for children, especially newborn, the 7x50 or 7x60
is optimum. With increasing age one should choice a 7x35 or 10x50, if
larger magnification is necessary. The retired hunter with a 8x60
demonstrates that he has earned enough money to buy that binocular but
also demonstrates missing knowledge in basic optics.
--
Kind regards
JA
Joerg Angerstein
Harvey N Rutt
> The exit pupil is the ratio of lens diameter and magnification. In
> case of 7x35 it is 5 mm, in case of 7x50 it is more than 7 mm. The dark
> adapted eye of a child can be as large as 8mm, adult have decreasing
> pupil diameter and at an age of 50 normally not more than 5mm. The
> result would be that for children, especially newborn, the 7x50 or 7x60
> is optimum. With increasing age one should choice a 7x35 or 10x50, if
> larger magnification is necessary.
Whilst the arithmetic is right - & I agree entirely about idiotic
designs with silly exit pupils - this reply ignores the issue of holding
the darn thing still enough!
Most kids would have no hope of holding a 7*60; just too big & heavy,
they are far better off with a dimmer or smaller image which is actually
in the field of view & not shaking all over the place!
Very few people can comfortably hand hold mag. >=10, & unless
experienced have trouble locating the subject too; many people of
'increasing age' would find 10*50 a pain to use.
Even for an experienced adult, 8*50 becomes a pain when tired, cold, its
windy etc let alone if you are on a boat! In such cases 8*30, 7*35, 8*40
will be much better choice depending on the balance of mag & brightness
you need; on a boat etc I'd go for 7* for sure. In most cases the bigger
aperture brings remarkably little benefit except for short periods at
dusk & dawn, under heavy overcast etc because the pupil is stopping
down. You pay the money, cart the weight about, & suffer the image shake
the rest of the time! But of course they make you look like a super
twitcher etc; you just dont actually see as much.....
Of course, if you are going to put it on a tripod its a different
matter, but *finding* & tracking things in the narrow field of view of
high mag. can still be an issue.
The above 'optimimum' is certainly true for brightness of the image; but
not in real life usage!
Harvey Rutt
Pete
I've seen a pair of binocs marked 16x50. According to the answers I
received, anything above 10x magnification is really heavy. '
What do you have to say about a pair of 16x50 binocs?
--
Pete
newm...@ihug.co.nz
Harvey N Rutt <h...@ecs.soton.ac.uk> wrote in article
<33D85F...@ecs.soton.ac.uk>...
Paul M. Brinegar, II
Pete wrote:
>
> I've seen a pair of binocs marked 16x50. According to the answers I
> received, anything above 10x magnification is really heavy. '
> What do you have to say about a pair of 16x50 binocs?
> --
One of the primary contributors to the weight of a pair of binoculars
are the two objective lenses. It seems to me that the 16X50's would
weigh much the same as a pair of 10X50's. The difference between them
being the relative focal lengths of the optics involved. The total
mass of glass and metal should be pretty close.
Most of the big binoculars (>10X) have significantly larger objectives
on them, such as 15X70, 15X80, and 20X80. That extra volume of glass,
and the metal to hold it in place, makes for one heavy pair of
binoculars.
PMB. (note the ANTI-SPAM in the email address)
Johannes Swartling
Pete wrote:
> I've seen a pair of binocs marked 16x50. According to the answers I
> received, anything above 10x magnification is really heavy. '
> What do you have to say about a pair of 16x50 binocs?
> --
> Pete
> newm...@ihug.co.nz
This reply may come in a little late, but anyway, here goes...
I visited my parents this weekend in our family summer house,
and my father had just bought a pair of used 16x50's which
had been used on a coast guard vessel. They were really light,
had fairly good optics and weren't too difficult to hold still
while standing on land (on a boat I suspect you have to be
a real pro). I really liked the high magnification and it was
no problem for me to hold them still, and I'm certainly not an
experienced user.
I guess the best way of deciding which binocs to buy is
to simply try them in the same conditions as you will use
them, and see what they feel like.
Johannes
John Wasser
Pete wrote:
> I've seen a pair of binocs marked 16x50. According to the answers I
> received, anything above 10x magnification is really heavy. '
> What do you have to say about a pair of 16x50 binocs?
High-magnification binoculars are not necessarily
heavy... They are just hard to hold steady.
To get the same light-gathering power as a pair of
7x50 binoculars they would need a front lens
over twice as large and that would tend to get
heavy. A 16x50 has the light-gathering power of
a 7x21... fine for daytime use.