You'll Never Guess (1 Viewer)

[OPTIC_NUT]

In my entire used/cleaned collection, and even among all the new binocs
(though I'm not into really high prices yet), one pair of binoculars
has the highest contrast and the sharpest resolution, by yards.
It's...

---An old Selsi 7x35 Galilean pair!
--coated front achromat, good focuser, a number of tight irses in lampblack

Of course, the image is slightly yellow (the usual anti-blue/UV effect),
and the field width is quite small (3 or 4 degrees, comes with the turf),

But the font test blows them all away and the field depth is high, and the
contrast can reveal all the subtle shades of a dimly side-lit fabric book
cover from 1890.

There is an unexpected gain to handheld resolution due to the lack of
prism weight and light shell (less muscle tremor).
It's definitely more than an opera glass.

So...what's the use? Well, now and then it's great for looking at the
little details of this special bird or that deer, but the main use is as a
benchmark for comparing other binoculars. Having a lot fewer surfaces
and a ton of irising (not productive for Keplerian) has an incredible effect.

Tracking (my moving license plate test) works well despite the narrow field
due to depth of field and easy pointing (the view under-reacts to eye
placement).

More fun than I figured originally. I wish someone made fish-eye
x7 Galileans that got up to 5-6 degrees view. 50mm curved-face things.

It clued me into a mitigating factor for roof-prism binocs:
while length damps hand shake, weight adds to it via tremor amplitude.
(the lighter weight of the roof binocs can make up for less tripod resolution:
same for smaller aperatures to some extent)

 

[Highway Dog]

Another detail to consider is to assess the magnification!

On your font tests and "worn lettering test" on poor contrast background, do you try to set up a standard distance? Isn't that distance pegged to the magnification strength of the binoculars?

If it marked wrong, and is stronger than 7x, then it would help do the tests.

Maybe you have already considered this idea.
Share your thoughts,
Rob.

 

[Gijs van Ginkel]

OPTIC_NUT,
I am a bit confused by you Gallilean binocular. This name is frequently used for very simple lenstype binoculars as invented in 1608 by the Dutch spectacle maker Hans Lipperhey and about one year later very much improved by Galileo Galilei. Such binoculars do not contain prisms and their magnifiction generally does not exceed 5x.
So is te term Gallilean a brand name and, if so, where does it come from?
Gijs

 

[OPTIC_NUT]

OPTIC_NUT,
I am a bit confused by you Gallilean binocular. This name is frequently used for very simple lenstype binoculars as invented in 1608 by the Dutch spectacle maker Hans Lipperhey and about one year later very much improved by Galileo Galilei. Such binoculars do not contain prisms and their magnifiction generally does not exceed 5x.
So is te term Gallilean a brand name and, if so, where does it come from?
Gijs

That's the type. It's the real generic name, not a brand.
A front convex lens and a back concave lens, small field of view.

Modern Galileans are rare but they do exist, with achromatic lenses.
Eschenbach produces spectacle binoculars of that type for dentists
and surgeons...for depth of filed and sharpness. They achieve field of view
using very large curved objectives, and their powers go up to 7x.
They are also very expensive.

 

[OPTIC_NUT]

Another detail to consider is to assess the magnification!

On your font tests and "worn lettering test" on poor contrast background, do you try to set up a standard distance? Isn't that distance pegged to the magnification strength of the binoculars?

If it marked wrong, and is stronger than 7x, then it would help do the tests.

Maybe you have already considered this idea.
Share your thoughts,
Rob.

The magnification looks just like that of regular 7x binoculars.
I always use the same distance, about 22 feet.
For practical ability to resolve, I test everything from 6x to 12x at the
same distance, with tripod and hand-held. Higher power binoculars do not
always have finer resolution, and held by hand, higher powers (like 10x+)
can results in no gain in practical resolution, due to hand-shaking.

These are a real 7x. Nobody that type uses them now because the
field width is very small. They are useful to me in seeing what the maximum
resolution can be and how deep the best contrast can be with only
a front coated achromat and a back concave.

 

[henry link]

I think this is the item that OPTIC NUT is writing about. A Galilean field glass trying its best to look like a Porro prism binocular.

http://www.worthpoint.com/worthopedia/vintage-selsi-lightweight-binoculars-1

You can click on the image to enlarge it. I remember the type well from the 1950s when I first became interested in binoculars as a kid.

FWIW a similar pair was prominently featured in the 2012 movie "Moonrise Kingdom". See below.

 

[ronh]

Hooray! That is an interesting report. It sounds like it must have achromat objectives--is that right? Do you know anything about the eyepieces? I have always wondered how good a Galilean style could be with good coatings and slightly complex lenses.

It seems often the story of someone's escape from the dreaded giant blocks of glass is glowing. I certainly see a similar thing in the cheap 8x finder on my astronomical scope, which gives a clearer central view than any of my expensive binoculars.

As a stargazer, I have always been fascinated by a 5x prismless Keplerian binocular shown and described in the (good!) book "The Telescope" by F. W. Bell. Sorry I can't remember now who made it, a German name. It was before the days of coatings, but had achromat objectives and cemented triplet eyepieces. With it's positive eyepieces it presents a much wider field of view than a Galilean, but the image is upside down. That wouldn't be such a bad thing for astronomy, at least there is a tale running around that certain chickens got used to it.

Prisms do invert the image but at a considerable cost: they suck. They are heavy, bulky, expensive and plagued with such fascinating optical difficulties that it's almost a subject in itself. Somebody, set us free! The idea that image inversion might be done electronically rather than with prisms keeps me interested in the CCD based binocular of the future.

I think he's looking the girl. It might have been the young Henry, oogling the handles on the field glass.

Ron

 

[OPTIC_NUT]

Yup, those are the ones (in the worthpoint link).

The ones in Moonrise Kingdom look like a cheaper type with stamped metal fittings
that were once a starter Boy Scout model. About 3x, chromatic bloom. A toy.
Hard to tell. Her binocs are a bit chunkier in imitating the prismatic shape.
Nice old 8x30s look like a bit the Moonrise Kingdom ones but give way better
performance.


So..the front lens is a coated achromat, and the eyepiece has a bi-convex lens.
No readily visible chromatic distortion. Of course, the chromatics of the eyepeice
would matter 1/7 as much, optically. The nicer opera glass have that layout too:
achromat front, flint back.

I'm still taking regular 7x35s and 8x40s out bird-n-critter-watching.
A 3 degree field is pretty limiting.

I have some French WW-I big galileans at about 5x. Very sharp, but less power.
Really heavy. They still produced a lot because the prismatic 8x25s were much
more expensive (about 3 times more) at the time.

You have to be careful with the WW-I Galileans. (the big ones)....There were a lot of
really bad imitations made in the 20th century....very low power and not sharp.
No achromats up front. Very similar brass, horrible lenses. Looks like the imitations
were made about 1920-1940, maybe to imitate war surplus. Best bought where you can
actually see through.

Exception: the old balsam up front is drying and the objectives are a crazed yellow mess.
That confirms an achromat, and you can soak with nail polish remover, clean off the pieces,
and make a clean objective with only a little light loss, air-spaced. Got a few bargains from
the 1800s that way. Nobody wants patina on the glass!

 

[Bencw]

I have some French WW-I big galileans at about 5x. Very sharp, but less power.
Really heavy.

I too have some WW1 French galileans, petit-fab-paris, but as you say, quite heavy and small FOV, they are still pretty sharp and clear though, so much so that my sister in law wants them for bird watching in her garden, preferred them to her own porro's.

 

[OPTIC_NUT]

The garden setting makes sense....less distance.
The depth of field means she doesn't have to bother with focus for a good
variance in distance. Hard to be narrow-field if you're seeking, but if you know
(nest, apple tree, feede,, post), you can do alright.