8x40 binoculars nowhere near 8x

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I got my binoculars out today (so I could read the signal strength display on my TV while tweaking the dish) and they are inscribed 8x40.

Now I thought that meant 8x magnification, and the hole at the business end is 40mm diameter (which looks about right).

If I use 1 eye through the binoculars, and the other unaided, the image only looks about 3x the size, nowhere near 8 times.

Am I doing something wrong, was I conned years ago when I bought them, or have the lenses thinned out with age?

Neil_Jones

https://www.harrisoncameras.co.uk/blog/guides/binoculars-buying-guide-choose-the-right-binoculars-for-your-activity_blog-bino - "

An 8X40 pair has an 8x magnification; a 10X40 pair has a 10x magnification and so on.

Magnification refers to how much bigger the image will appear compared to the naked eye.

If you're looking at a subject with a 10X40 pair of binoculars, then the subject will appear 10 times bigger than if you were looking at it with the naked eye.

It is always tempting to get the highest magnification in binoculars, because logically, you would think that the more magnification you have the better the image.

Well according to science and possibly a very, very long formula, the more magnification you have, the less light reaches the eye.

So in the day to day world of binoculars, 20x binoculars, may sound fantastic, but unless the objective lens is really big, the image will be less clear than if you have a 10x42 pair."

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Thanks,

but the problem is they say 8x40 on them, but if I look at a distant object with one eye through the binocular, and one eye without, the image only appears to be about 3 times larger.

They aren't zoom ones turned down either.

EDIT:

I found another pair with "Made in Japan" stamped on. these do make the image about 8x bigger, so the batteries must have gone in the first pair

Grey_Critic

Why do you need Binoculars to test signal strength? A compass yes so you can check a Satelite dish alignment I can understand

Don't think ther Binoculars are strong enough for you to see tha Satelite from your house - think the clouds will get in the way and the way those things wizz around and the number of them it will be hard to identify the correct one or read the model numbers - the writing is quite small.

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Grey_Critic said:

Why do you need Binoculars to test signal strength? A compass yes so you can check a Satelite dish alignment I can understand

Don't think ther Binoculars are strong enough for you to see tha Satelite from your house - think the clouds will get in the way and the way those things wizz around and the number of them it will be hard to identify the correct one or read the model numbers - the writing is quite small.

I can see the TV screen from up the ladder, I can just read the on-screen signal information with my 8 3x40 binoculars

debitcardmayhem

Batteries in binoculars ? are you sure you don't mean your hearing aids

EDIT: Perhaps you may be better using your smart phone camera and zoom

GDB2222

What does 8 times bigger mean? 8 times bigger in each dimension?

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GDB2222 said:

What does 8 times bigger mean? 8 times bigger in each dimension?

They (should) make objects appear 1/8 of the distance away (8 times closer), so 8x bigger vertically & horizontally.

Looking at a distant house with one eye through the binoculars and the other eye not, with my Japanese ones the image is about 8x taller than real life, but only about 3x taller with the first pair of no brand made nowhere ones.

I posted in case I was misunderstanding something about how I was measuring the magnification, turns out I wasn't and the first pair are more like 3x40. I bet they have mirrors inside not prisms as well!

Norman_Castle

Are you reading a 3 as an 8?

tempus_fugit

GDB2222 said:

What does 8 times bigger mean? 8 times bigger in each dimension?

This is a good question. To me “8x bigger” is simple in one direction, but when you have two dimensions as in a binocular view, I think most people reckon 8x bigger means 8 times longer in each dimension, whereas I do not think that will be the case. Because there are 2 dimensions effectively the proportion has to be squared. So something 2x as big in each direction is 4x as big overall. And something 3x as big in each direction is actually 8x as big (3 to the power of 2). So it sounds to me like the binoculars are magnifying things as I would expect.

k_man

With binoculars/optics the magnification level refers to linear dimensions, not size of area.

So, as above, 8x should make the object 8x as high and 8x as wide (as if the object were 1/8th the distance away).

This is how the the Made in Japan binoculars behave.

What the general public understand as 8x bigger is not what matters, as the terms for binoculars have specific definitions.