Unnatural geometry of "field-flattened" binoculars? (1 Viewer)

[MartinDCZ]

Hello folks,

Been a long time since I was here last.
I've come in search of an advice from more experienced binocular users that I haven't been able to find so far.

As I've been using my Endeavor EDII 8x42 extensively since the day I got it, I noticed the usual downsides of this particular design (lack of 3D perception, rolling ball, diffraction spikes...), but it took long time to notice one particular phenomenon.

As a lot of the observed objects (and I'd imagine this would especially be true for birders) are of irregular or asymmetrical shapes, it may evade notice.

How I even noticed it in first place was peculiar too; I was watching from above some OB trucks departing from garages.

Naturally, when you watch that kind of box-shaped object, the parts that are further from you appear smaller, even though you know the box-shaped object has the same height, depth and width throughout.
That's what creates the 3D perception.

But when viewed through the ED II, this perception is changed. The binocular projected the box-shaped truck with what appeared to be a sort of 'orthographic' view, rather than a perspective view:

https://www.google.cz/search?biw=19...k1j0i30k1.0.Cjj6DxsZots#imgrc=J8n5dlMQdIv4JM:

That is, if the dimensions are equal, the ED II shows them as equal, regardless of the angle of attack, the small, but still non-zero relative distance...

My other pair of binoculars (Nikon Aculon 16x50) is ridden with multitude of other flaws, but it simply doesn't do that.

The rolling ball effect is something that's not very kind to my eyes but I kind of got used to that. The unnatural view rid of 3D perception however (which I think has a lot more to do with the orthographic projection rather than the roof-prism construction - hence the objective lenses not being far apart enough) is kind a hard blow.

Now, I know that obviously some field flatteners are more equal than others, but I wonder if this phenomenon is, to some extent, typical to all binoculars with field flattener lenses.
If so, I think I'll want to avoid them from now. I'd much prefer binoculars that have a natural, three dimensional, perspective view, don't confuse my brain when panned and have a wide AFOV with a reasonable part of it in focus, rather than all of it sharp, but at a steep price of an image that doesn't make sense.


Thanks in advance.

Martin

 

[WJC]

Hello folks,

Been a long time since I was here last.
I've come in search of an advice from more experienced binocular users that I haven't been able to find so far.

As I've been using my Endeavor EDII 8x42 extensively since the day I got it, I noticed the usual downsides of this particular design (lack of 3D perception, rolling ball, diffraction spikes...), but it took long time to notice one particular phenomenon.

As a lot of the observed objects (and I'd imagine this would especially be true for birders) are of irregular or asymmetrical shapes, it may evade notice.

How I even noticed it in first place was peculiar too; I was watching from above some OB trucks departing from garages.

Naturally, when you watch that kind of box-shaped object, the parts that are further from you appear smaller, even though you know the box-shaped object has the same height, depth and width throughout.
That's what creates the 3D perception.

But when viewed through the ED II, this perception is changed. The binocular projected the box-shaped truck with what appeared to be a sort of 'orthographic' view, rather than a perspective view:

https://www.google.cz/search?biw=19...k1j0i30k1.0.Cjj6DxsZots#imgrc=J8n5dlMQdIv4JM:

That is, if the dimensions are equal, the ED II shows them as equal, regardless of the angle of attack, the small, but still non-zero relative distance...

My other pair of binoculars (Nikon Aculon 16x50) is ridden with multitude of other flaws, but it simply doesn't do that.

The rolling ball effect is something that's not very kind to my eyes but I kind of got used to that. The unnatural view rid of 3D perception however (which I think has a lot more to do with the orthographic projection rather than the roof-prism construction - hence the objective lenses not being far apart enough) is kind a hard blow.

Now, I know that obviously some field flatteners are more equal than others, but I wonder if this phenomenon is, to some extent, typical to all binoculars with field flattener lenses.
If so, I think I'll want to avoid them from now. I'd much prefer binoculars that have a natural, three dimensional, perspective view, don't confuse my brain when panned and have a wide AFOV with a reasonable part of it in focus, rather than all of it sharp, but at a steep price of an image that doesn't make sense.


Thanks in advance.

Martin

180209

Hi, Martin:

First, the two EASY points.

The 3d effect is purely a product of how far the objective lenses are spaced. In addition, true stereopsis is only valid at short distances.

Secondly, I think most members would agree that the size a truck bed does not offer adequate data points to make a judgement between a perspective vs. an orthographic view. Often, what we THINK we see ... we do not. Please see attached from BINOCULARS: Fallacy & Fact. It is OBVIOUS that the right side of the image is darker than the left. At least, until a couple of fingers are laid on the middle of the image. Then it becomes clear that both sides are equally dark!

Finally, since 1949 most optical engineers have added a bit of pincushion distortion to the image to mitigate the effects of "roller ball." Were it not so, distortion could be completely done away with at the expense of a lot of annoying roller ball effect. In optical engineering one "size" does not fit all. :cat:

I hope you find this helpful.

Bill

 

[Chosun Juan]

Martin,

As Bill says, the strictly technical definition of 3D or 'stereopsis' effect is a function of objective spacing only.

However, the 'perception' of a '3D' effect can be subject to many other optical physiology and even physiological factors. There is wide variation in the perceptions of this so it's very much an individual thing (witness those who swear there's some sort of voodoo 3D magic going on with the Leica NoctiVid, and yet others who regard it as a 3D meh).

If Brock still roamed these parts, then hopefully he had it drummed into him often enough to realize and relay to you, that each of us has different amounts of barrel distortion in our eyes which affects the perception of the 'rolling ball phenomenon', and indeed the 3Dness' of the world we individually see (within the normal distribution and limitations of a shared human physiology and DNA of course!

Don't confuse Angular Magnification Distortion for Field Curvature effects. Also, distortion profiles (as indeed our eyes) are rarely linear, being rising (or falling) rate, or even with points of inflection - the so called 'mustache' distortion - so often the effects to our eyes are field position dependent.

My own Zen ED3 has what I would describe as 'wild' pincushion :hippy: which strangely gives quite a good 'quasi' 3D effect (though not enhanced stereopsis when compared to a regular Porro I). Most Canon IS bins that I have seen have the distinct impression of being cardboard flat. Yet the 'flat field' Swarovski 10x50 SV has quite a good walk in view and impression of 3Dness for a sharp to the edge roof design. Go figure.

Short story - between the 'vagueness' around various optical terms in practical use, and a few more individual psychological factors thrown in, hard and fast conclusions can be a slippery slope to confusion!

As this particular aspect is just one factor in the view, best advice is I suggest you just ignore it completely and without prejudice find something you like the look of - sharp to the edges or not. :t:



Chosun :gh:

 

[typo]

Martin,

I've had a Endeavour EDII 8x42 for a few years now. Yes, like most models with a field flattener, it does have magnification distortion. I really don't find it troublesome in the natural environment but it does have some odd properties in the man made world. Just studying single bricks in my garden wall, they can appear to have normal perspective, orthogonal or reversed perspective depending on where they are placed in the field of view. I see rolling ball quite clearly when panning past industrial building but really can't detect it in open countryside.

Few flat field binoculars are as flat as the Vanguard. The original Swarovski EL Swarovision 8.5x42 should probably be credited with launching the fashion for flat field dual hinge binoclars. Originally, it had a pronounced moustache distortion, with a ripple in its magnification which I found disturbing, even in the natural world. Fortunately that has been somewhat tamed over the years. The Hawke Frontier ED and Sapphire ED are close relatives of the ZenRay CJ mentions. They could be quite nausiating at times. We think the Bushnell Legend M might be the latest incarnation of that model line and that seemed less bothersome. There are a number of other nearly flat designs like the Nikon EDG and the Kowa Genesis which sufficient pincushion for me but maybe not for the most sensitive users.

Generally I prefer lower power models to have both pincushion and field curvature. At 10x or above I seem to be rarely bothered by the magnification distortion effects, and I'm happy to use either. I might be more particular if I was interested in manoeuvring trucks.

David

 

[MartinDCZ]

Thanks for the help guys, after some trying I have to restate some of the things I wrote, I tried comparing the Nikon (Aculon A211 16x50) and the Vanguard (Endeavor ED II 8x42) again and found that the Nikon in fact does produce the same kind of orthographic picture, BUT: it has more pincushion distortion than the Vanguard, hence no rolling ball effect; I suspect the vanguard, at least when I look through it, has a barrel distortion. I tried taking pictures through both and when taken with a camera, the pictures of box-shaped objects from the Vanguard appear natural (but then the sensor in my camera phone is flat and very tiny, unlike my retina lol).

I'm not entirely sure why I noticed this with the Vanguard and not with the Nikon that I owned for a longer time. Possibly because of the double magnification and narrower true FOV, so I couldn't these kind of objects whole as they didn't fit in the field of view, maybe because I wasn't paying attention to them in the first place. Idk..
It's a pity it the camera doesn't capture what I actually see in the Vanguard (or I think I see, anyway).
I'll try to describe it best I can and please correct me if I'm wrong identifying the type of distortion.

When I look at a flat plane, such as a flat TV screen, at a normal angle, and fill almost the entire FOV with it, all of it's edges look straight and all of it is in focus. So far so good. If there was either a barrel or pincushion distortion, the screen wouldn't appear flat, but curved either convex or concave, right?

But when I look at it under other than normal angle, e.g. 45°, and stand in a distance where the apparent width of the screen fills half of the FOV, the appearance of the rectangular shape changes depending on the placement in the field of view; if I place the vertical edge of the screen that is physically closer from where I stand near the field stop, and the vertical edge of the screen that is physically further from me at the center of the field, it appears the far vertical edge (one in the center of the field) is magnified more than the near edge (at the field stop), creating an optical illusion where the rectangular screen appears as trapezoidal. As I shift it horizontally, placing the (physically) near vertical edge of the screen towards the field center, and the far edge towards the field stop (on the opposite side), this illusion progressively decreases, until it's invisible and the flat rectangle placed in a three dimensional space viewed from an agnle once again looks like it should look (or at least the way I want it to look). This then, would imply higher magnification in the center than near the field stop (barrel distortion), but only when viewed at a different than normal angle; another possibility is that my short sighted eyes adds a certain amount of barrel distortion (?), meaning I should look for binoculars with sufficient pincushion distortion to cancel out the globe effect and the orthographic effect.

What I don't understand however is, when I tested the view at a flat rectangular screen under a not-normal angle with the vanguard, and took pictures, the snapshots of the screen looked natural, regardless of its placement in the FOV (as opposed to my own sight). When I did the exact same thing with Nikon, again, a flat rectangular screen, under a not-normal angle, shifted from trapezoidal to rectangular depending on the placement, but when I took a picture through the Nikon, insted of appearing natural, the screen (when centered across the FOV) looked like a pincushion, instead of a rectangle.
Well damn. I'm so confused now.

 

[Binastro]

Some of the Aculon and Action VII Nikons have aspheric eyepiece elements. The distortion and magnification change across the field. It may be that the 16x50 has spherical curves only in the eyepiece elements.

3D is not determined by objective spacing only.
It is determined by the product of magnification and objective spacing.
I clearly see 3D in reverse Porroprism binoculars as the magnification in normal magnification binoculars far outweighs objective spacing.

 

[MartinDCZ]

Yes that's right the Aculon A211, including the 16x50 i believe, are supposed to have some aspheric elements in the eyepieces, that's I suppose to improve edge sharpness (which with this particular model isn't too great anyway).

Do you think it's possible for me to make a conclustions that,
1) the picture taken by camera is more or less accurate of what the binoculars project,
2) the Vanguard is mostly free of distortion, but my eyes turn the view into barrel distortion under certain angles
3) the Nikon has pincushion distortion that my eyes turn into barrel distortion anyway, only not as prominent
?

 

[Steve C]

You are likely seeing parallax looking at the angles you describe. Ever look at the speedometer needle from the passenger seat? Notice how what speed you read is different from the actual speed? The error is parallax.

 

[Chosun Juan]

THE! Definitive Distortion guide

Whoa! Martin 3 You are going to do your head in !! :bounce:

Too much going on from too many unidentifiable sources to quantify.

Here's how you assess any optics:

Turn it around and look through the objective end at a screw head with a vertically aligned slot - this mostly takes the distortions of your eyes/glasses out of the equation.

Stand directly in front of it and place the screw head in the centre of the field - now move the target horizontally to the edge of the field and note what happens. Does the screw head become larger or smaller? Elongated in the horizontal or vertical directions? Does the slot of the screw head bow one way or the other? What happens to sharpness? :cat:

There! You now have a precise picture of all the individual distortions in your binocular and have saved reams of Internet pages discussing 'opinion' (yours and theirs - and ne'er the twain shall meet with other folks! :king:

Just remember that what you see is in reverse. ie. Barrel distortion appears as pincushion and vice versa. The AMD size effects are reversed, and so is the field curvature. With a suitable target you could also add CA into the equation. Carefully note the changes as you progress across the field to get an accurate picture of the distortion profile curve.

You can repeat the exercise moving vertically in the field (from Centre to top or bottom), and might even try it radially.

You could also repeat the process standing at 45° from your target to compare, and even use a small square nut too as your target.

Of course carefully photographing these tests at 'normal' focal lengths will give you an accurate record too. You may also want to add a grid mesh (graph paper) target too.

You (or anybody else) now have the facts, and the endless circular (*teehee*) discussions of 'opinion' here on BF can cease ..... though what folks will do with their new found time is beyond me! o Lol



Chosun :gh:

 

[WJC]

Some of the Aculon and Action VII Nikons have aspheric eyepiece elements. The distortion and magnification change across the field. It may be that the 16x50 has spherical curves only in the eyepiece elements.

3D is not determined by objective spacing only.
It is determined by the product of magnification and objective spacing.
I clearly see 3D in reverse Porroprism binoculars as the magnification in normal magnification binoculars far outweighs objective spacing.

Binastro:

Undoubtedly, the 3D EFFECT may relate to more than objective spacing.
However, will you admit clinical stereopsis (free of other physiological interference) relates exclusively to objective spacing? I am eager to learn new things. But, having dealt with that issue so long, I would need some academic clarification from a credentialed optical engineer. If you can provide that, you would be helping me immensely and I would be most grateful. :cat:

Bill

 

[Binastro]

I think that Holger Merlitz comes to the same conclusions as I did long ago. But his book is in German, and I don't know the reference page/s.

It is very simple to verify if one has reasonable binocular vision.
One sees how far binocular vision extends with known targets, and unaided eyes and different binoculars, different magnifications, and same separation as IPD, and less with reverse Porroprism, and more with normal Porroprism binoculars.

Yes, clearly objective separation is a factor and a big factor in naval rangefinders with metres objective separation, but one has to multiply it by magnification, although different rangefinding systems give slightly different results.
The British system is different to the American.
There have been tests with young but experienced naval personnel using both systems out to about 15,000 yards.

I also think that vernier acuity is involved in certain targets.

Contrast must be high with good light. I use known buildings.

Surprisingly to me the roof line of my unaided eyes test building is not so easily seen in 3D with a clear sky as with a cloudy sky. I don't know the reason.

It is also difficult sometimes to separate artificial 3D from genuine 3D effects.

Nowadays, my eyes need to be well rested but earlier this wasn't such a big factor.

No one can see with another person's eyes, but 3D is basic. Magnification x objective separation and acuity with well aligned binoculars and eye separation and acuity with unaided eyes.

P.S.
No, I do not accept that 3D relates exclusively to objective separation.
It is the product of magnification times objective separation.

One needs a background miles away, preferably clouds or sky.

Perhaps somebody with Holger Merlitz's book can give the reference pages and translate.
My German is not good enough to have bought the book.

 

[WJC]

I think that Holger Merlitz comes to the same conclusions as I did long ago. But his book is in German, and I don't know the reference page/s.

It is very simple to verify if one has reasonable binocular vision.
One sees how far binocular vision extends with known targets, and unaided eyes and different binoculars, different magnifications, and same separation as IPD, and less with reverse Porroprism, and more with normal Porroprism binoculars.

Yes, clearly objective separation is a factor and a big factor in naval rangefinders with metres objective separation, but one has to multiply it by magnification, although different rangefinding systems give slightly different results.
The British system is different to the American.
There have been tests with young but experienced naval personnel using both systems out to about 15,000 yards.

I also think that vernier acuity is involved in certain targets.

Contrast must be high with good light. I use known buildings.

Surprisingly to me the roof line of my unaided eyes test building is not so easily seen in 3D with a clear sky as with a cloudy sky. I don't know the reason.

It is also difficult sometimes to separate artificial 3D from genuine 3D effects.

Nowadays, my eyes need to be well rested but earlier this wasn't such a big factor.

No one can see with another person's eyes, but 3D is basic. Magnification x objective separation and acuity with well-aligned binoculars and eye separation and acuity with unaided eyes.

Thank you so much; I'll send him an email, Monday!

Bill

 

[typo]

Martin,

With my Vanguard I can see no hint of barrel distortion at all, only the slightest touch of pincushion right at the edge of the view. There is magnification distorton as I said.

David

P.S. My ZenRay Prime 10x42 would also be called a flat field design. However, there is just a little field curvature and much more pincushion than the Vanguard. The bricks in the wall maintain a constant normal perspective across the field of view.

 

[Holger Merlitz]

Hello folks,

Been a long time since I was here last.
I've come in search of an advice from more experienced binocular users that I haven't been able to find so far.

As I've been using my Endeavor EDII 8x42 extensively since the day I got it, I noticed the usual downsides of this particular design (lack of 3D perception, rolling ball, diffraction spikes...), but it took long time to notice one particular phenomenon.

As a lot of the observed objects (and I'd imagine this would especially be true for birders) are of irregular or asymmetrical shapes, it may evade notice.

How I even noticed it in first place was peculiar too; I was watching from above some OB trucks departing from garages.

Naturally, when you watch that kind of box-shaped object, the parts that are further from you appear smaller, even though you know the box-shaped object has the same height, depth and width throughout.
That's what creates the 3D perception.

But when viewed through the ED II, this perception is changed. The binocular projected the box-shaped truck with what appeared to be a sort of 'orthographic' view, rather than a perspective view:

https://www.google.cz/search?biw=19...k1j0i30k1.0.Cjj6DxsZots#imgrc=J8n5dlMQdIv4JM:

That is, if the dimensions are equal, the ED II shows them as equal, regardless of the angle of attack, the small, but still non-zero relative distance...

My other pair of binoculars (Nikon Aculon 16x50) is ridden with multitude of other flaws, but it simply doesn't do that.

The rolling ball effect is something that's not very kind to my eyes but I kind of got used to that. The unnatural view rid of 3D perception however (which I think has a lot more to do with the orthographic projection rather than the roof-prism construction - hence the objective lenses not being far apart enough) is kind a hard blow.

Now, I know that obviously some field flatteners are more equal than others, but I wonder if this phenomenon is, to some extent, typical to all binoculars with field flattener lenses.
If so, I think I'll want to avoid them from now. I'd much prefer binoculars that have a natural, three dimensional, perspective view, don't confuse my brain when panned and have a wide AFOV with a reasonable part of it in focus, rather than all of it sharp, but at a steep price of an image that doesn't make sense.


Thanks in advance.

Martin

I guess what we see here are effects of the distortion. Field flattener often reduce pincushion distortion and thus generate a close to orthoscopic projection of the image. Straight lines remain straight, but once you observe an object close to the edge of field, it appears unnaturally squeezed. This is of course the result of AMD that comes along with the orthoscopic projection: If a sufficient amount of pincushion is added, to satisfy the angle condition, then all angular distances remain unchanged while moving the object around. It is like gazing onto a flat poster (orthoscopic) vs. gazing into a vault (angle condition). In this manner, particularly while panning, an image with low AMD appears more natural and perhaps also rather "3D", even though no stereopsis is involved here.

Cheers,
Holger

 

[Nixterdemus]

"It is OBVIOUS that the right side of the image is darker than the left. At least, until a couple of fingers are laid on the middle of the image. Then it becomes clear that both sides are equally dark!"

I don't see it, w/2 fingers or the whole hand, though left eye only w/mild cataract the left is a slightly darker hue. The IOL replacement in me dominate right alone shows even less of a change to the dark side.

May the force be w/youse guys.

 

[MartinDCZ]

THE! Definitive Distortion guide

I will definitely try that, thank you for the tip.

I guess what we see here are effects of the distortion. Field flattener often reduce pincushion distortion and thus generate a close to orthoscopic projection of the image. Straight lines remain straight, but once you observe an object close to the edge of field, it appears unnaturally squeezed. This is of course the result of AMD that comes along with the orthoscopic projection: If a sufficient amount of pincushion is added, to satisfy the angle condition, then all angular distances remain unchanged while moving the object around. It is like gazing onto a flat poster (orthoscopic) vs. gazing into a vault (angle condition). In this manner, particularly while panning, an image with low AMD appears more natural and perhaps also rather "3D", even though no stereopsis is involved here.

That's what I needed to know. Thank you so much Holger.¨


Martin

 

[Nixterdemus]

Looking at the geometrical distortion box you'll note "Choose A Specimen". I found the Diatom, Intel Pentium Processor & Spirogyra exceptional examples for manipulating distortion. The distortion bar will move in 1* from 0-15* either positive or negative all the while showing the effect on chosen specimen along w/grid on the right showing the same degree of distortion.

 

[henry link]

Of those four examples the first one, No Distortion, doesn't actually exist in binocular fields. When lines are straight like the illustration the squares toward the field edge will always be distorted into rectangles by Angular Magnification Distortion.

The second example, Barrel, is very rare in binoculars and the fourth example, Mustache, is shown reversed from the way it appears in binoculars where pincushion is in the central part of the field and reverses toward the field edge.

 

[Nixterdemus]

Thanks for the corrections applied to bins Henry.

The thumbnail was a photography example w/link a Nikon microscope mini-tutorial. Both found snooping around for visual interpretations.

BTW, the Barrel Distortion example is what I see looking through the objectives of at least some of my bins at a 15 pane[3 across/5 down vertical rectangle] glass door. I center nine of them at 6-5' 8-10 X.

 

[henry link]

BTW, the Barrel Distortion example is what I see looking through the objectives of at least some of my bins at a 15 pane[3 across/5 down vertical rectangle] glass door. I center nine of them at 6-5' 8-10 X.

Yep, if a binocular has pincushion distortion when viewied through the eyepiece it will reverse to barrel distortion when viewed through the objective.

Henry