Binoculars with Compass

[mintyspilot]

Originally Posted by hellosailor

"The biggest factor in getting a CLEAR image is the aperture of the binoculars"
Totally disagree, as do most every maker and reviewer. What aperature buys you is BRIGHTNESS and light gathering ability, and that's all.

Sorry, but you are wrong on this. An image formed by optics is made up of a tiny mosaic of dots called "Airy discs" and like any mosaic the smaller the tiles the more life like the image. In optics, a larger aperture produces a smaller Airy disc ( see here http://en.wikipedia.org/wiki/Airy_di..._of_Airy_Disks ). The bigger your lens then the finer the image quality. Also see this

"The resolution of an optical imaging system — a microscope, telescope, or camera — can be limited by factors such as imperfections in the lenses or misalignment. However, there is a fundamental maximum to the resolution of any optical system which is due to diffraction. An optical system with the ability to produce images with angular resolution as good as the instrument's theoretical limit is said to be diffraction limited.

The [crispness and clarity of the image] of a given instrument is proportional to the size of its [main lens], "

http://en.wikipedia.org/wiki/Diffraction-limited_system

Originally Posted by hellosailor

You could have a six inch aperature, and if the binoculars aren't perfectly aligned, with outstanding coatings and top quality glass free of aberrations, you're just going to have a very bright pair of coke bottles.

I simplified for the sake of my explanation, but of course if the other optics in the binos are rubbish then it does not matter how good the images formed by the main lenses are. I didn't discuss chromatic aberration, spherical aberration or astigmatism either.

Coatings do make a difference. Bloomed lenses will transmit somewhere between 5-10% more light than unbloomed lenses. Roof prisms will be less likely to get misaligned if you drop the binos as they are a solid piece of glass but they are expensive to produce well compered to porro prisms.

But it ALL comes down to the image formed by the main lens. It has to be as good as possible. You cannot start with a rubbish image and magically make it better with coatings and prisms and the biggest factor for a good image is a big aperture.

So I'll modify my previous statement. A large aperture with a low magnification will produce a brighter, crisper image with a bigger field of view providing that the rest of the binos are not made from junk and are mechanically sound.

If you go to the world's most expensive binocular maker and pick up a top of their range 7x50 and another top of their range 7x30 then the 7x50 will give the better image. Similarly the 7x50 will give a brighter, crisper image than a pair of 20x50s from that maker but the 20x50 will give a bigger image with a smaller field of view.

I'll also agree that other factors such as weight are important too and NO binos should be bought without testing them.

Here are some simple tests that you can do without needing an optical workshop handy.

The best test for binoculars is to look at a bright star on a dark night. If there are two stars then the alignment is out. If the star is not a tiny dot then the optics are not top quality. Stars near the edge of the field of view will probably turn into tiny triangles pointing towards the centre of the field of view. The better the binos, the nearer the edge this starts. Poor binos will show this problem much nearer the centre of the field of view.

In daylight find something vertical and straight (like a mast or a flagpole) and pan it across the field of view so it appears on (say) the left, passes through the middle of your view and disappears out the right of you view. It should remain straight and vertical at all times, but pay attention as it reaches the edge of the field as you may notice it beginning to curve. The more it curves, the worse the binos. To test for colour trueness (lack of chromatic aberration) view something bright and white near the edge of the field of view. If it goes blue or shows coloured edges (blue on one side and red/orange on the other) then the binos are not properly colour corrected. Also look at the image quality. It will be pin-sharp in the centre of the field of view and will get progressively worse near the edge of the field of view. Better binos will be less fuzzy near the edge and have a larger sharp area in the centre of the field.

[capt_douglas]

One thing I've been talking to the tooth fairy about is stabilized binoculars. I had a chance to try a pair on a delivery and they really made an impression. They're more expensive than non-stabilized, heavier, and require batteries, but they sure do make looking more pleasant.

[hellosailor]

Totally out of context, minty. Airy disks have no practical bearing on binoculars, which are not "diffraction limited" super-optics that they might be more relevant to.

Again, ask Leica, Swarovski, Steiner, Nikon, Fujinon...None of them will tell you that size is all that matters. None of them will tell you that Airy disks are a factor here. Perhaps the whole industry is lying and only academia or arcana has the truth. You feel free to believe that if you want to, others can do their own research and see that no discussion or review of "civilian" binocs, to be found anyplace, mentions Airy disks as being an issue of relevance.

And while reconaissance satellites all have "cameras" on them, the issues that affect cameras and optics of THAT extreme caliber, simply don't apply to what we use in ordinary life. That kind of camera may well be "diffraction limited" but even then--that's a limit encountered AFTER all the others have been passed.

Big cheap binocs have been a tourist staple (rip-off) in warm destinations for decades. Wow, $25 for a pair of Nogo 12x50's, must be great....Not.

[mintyspilot]

Originally Posted by hellosailor

Totally out of context, minty. Airy disks have no practical bearing on binoculars, which are not "diffraction limited" super-optics that they might be more relevant to.

Since all images - whether binoculars or "super optics" - are composed of a mosiac of Airy discs, you simply cannot get past the resolution issue. Fact.

Originally Posted by hellosailor

Again, ask Leica, Swarovski, Steiner, Nikon, Fujinon.... Perhaps the whole industry is lying and only academia or arcana has the truth.

Perhaps they are. They have a vested interest in selling you their products for as big a profit margin as possible. If you think an entire industry doesn't make things up for marketing purposes then I've got some bad news for you - they do it all the time. I've seen it in everything from ultrasonic pipeline inspection systems right through to shampoos. Most product features are hype, pure and simple.

Having said that, I suspect we will continue to differ on this matter so it is probably best if we agree to disagree before the Mods get stuck in to us.

[noelex 77]

Wow maybe binocular threads will become more entertaining than anchor threads.
Mintyspilot your advice on binocular selection is excellent, I particularly liked the practical tests you proposed, but I am afraid most of you optics theory is not relevant to binoculars.
For anyone buying binocular take the time to look through a really good pair like Leica or Swarovski, particularly under low light conditions, they will show you what is possible.The difference is from middle of the road binoculars is amazing

[mintyspilot]

Originally Posted by noelex 77

Wow maybe binocular threads will become more entertaining than anchor threads.

Perhaps so, but I feel we are getting away from the original purpose of the thread and so I should probably shut up.

Originally Posted by noelex 77

Mintyspilot your advice on binocular selection is excellent, I particularly liked the practical tests you proposed, but I am afraid most of you optics theory is not relevant to binoculars.

If it helps you select a decent pair of bins then I'm happy enough with that.

[Christian Van H]

I am of the "bigger is better for light gathering" camp too. I have a 16" reflector (that I built) out in the garage, and I challenge anyone to haul ANY refractor 6" or less out and see more then I do. Just cant happen, as SIZE MATTERS when gathering photons...which has very little to do with sharpness or distortion (Dont forget atmospheric distortion). Nothing beats a bigger light bucket. For boat binocs, 50mm is about as small as I'd like to get...and you would agree if you were entering Boston harbor at dusk with about a zillion lights flashing and blinking all around. The magnification power is limited to how stable the platform is. Unstablized binos are limited to around 7X power as much more is impossible to hold steady enough to make out what you need to make out. Not much is more frustrating than looking at a buoy for 3 min. trying to get the number off the damn thing and having it be impossible to keep in view or keep in focus.

[unbusted67]

Wow guys thanks for totally highjacking this thread. Sheeesh!

[Christian Van H]

Hey, ya got 37 posts on a question about cheap binoculars...what did you expect?

[unbusted67]

Originally Posted by Christian Van H

Hey, ya got 37 posts on a question about cheap binoculars...what did you expect?

haha i should just be thankful

[Bash]

Originally Posted by unbusted67

Wow guys thanks for totally highjacking this thread. Sheeesh!

I grow weary of a tendency I've noticed in the past couple months where an OP feels that s/he owns a thread that s/he has initiated. Since when does someone own a conversation?

I suspect that most of us, at a social gathering, would not object to divergences in a conversation we've initiated. Why should the rules of social nicety change here on Cruiser's Forum?

These threads are conversations. Any member can begin one, but once you pose a question here, it becomes part of the forum's domain.

Far too often, these days, people on this forum complain about not getting the advice they wanted from the people they wanted to hear it from. Hey, it's free advice, and it may not be worth more than what you paid for it. On the other hand, if you already know the answer you want to hear, why bother asking the question?

[sck5]

I got my fujinons on ebay. great binocs and a great price. it pays to keep an eye on what is happening on ebay - there are good deals every now and then

[svHyLyte]

Originally Posted by unbusted67

Wow guys thanks for totally highjacking this thread. Sheeesh!

It seems that, in most cases, the answers appearing on the first page or so of a new thread are the most relevant. Thereafter thread drift accelerates. It is unfortunate that one cannot terminate one's own thread once a question has been adaquately addressed. I frequently see posts/answers to threads that are several years old which seems like a waste of bandwidth.

Hopefully the information you did receive--to say nothing of the added education--was of some use.

FWIW...

[unbusted67]

Easy on the righteousness there dude. It was said in a joking manner.

Originally Posted by Bash

I grow weary of a tendency I've noticed in the past couple months where an OP feels that s/he owns a thread that s/he has initiated. Since when does someone own a conversation?

I suspect that most of us, at a social gathering, would not object to divergences in a conversation we've initiated. Why should the rules of social nicety change here on Cruiser's Forum?

These threads are conversations. Any member can begin one, but once you pose a question here, it becomes part of the forum's domain.

Far too often, these days, people on this forum complain about not getting the advice they wanted from the people they wanted to hear it from. Hey, it's free advice, and it may not be worth more than what you paid for it. On the other hand, if you already know the answer you want to hear, why bother asking the question?

[rourkeh]

My vote is for Steiner, I have a set of stabilized, built in compass, awsome optics and I had them 5 years before the battery died. Cheap is ok on some things but I consider binocs a saftey related item, and I won't cut corners on things that can keep me alive. Boat = break out another thousand.