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Binocular Evolution I: Field of View (1 Viewer)

kimmik

Well-known member
United Kingdom
Cool comparison, Komz and Kowa look like curved field with low pincushion, so then all 4 combinations of field curvature/AMD do exist in current binoculars.
 

henry link

Well-known member
Notice that the distortion in the Komz and the Kowa is not straightforward pincushion. It's mustache distortion, caused by pincushion that increases across the inner part of the field in the normal manner, but then reverses in the outer part giving a line near the field edge the appearance of a handlebar mustache. The result is low AMD across most of the field reversing to high AMD near the field edge.

The conclusions reached in the thread "Binocular Evolution II: Distortion and Curvature" about a supposed relationship between the correction of field curvature and distortion were simply incorrect. There is no relationship between the type and amount of rectilinear or angular magnification distortion and field curvature. For a good example of a flat field binocular eyepiece with enough straightforward pincushion to completely correct AMD check out the older Canon IS models as well as the newer 32mm models. To find eyepieces with even more pincushion combined with well corrected field curvature see the Televue Panoptics and Naglers.
 

Binastro

Well-known member
Komz 6x24 Bin 2 1977.

In very dull completely cloudy conditions the view through the 6x24 is rather dull.

There is very slight barrel distortion near the edge.

There is angular magnification distortion towards the edge. Things are squashed.

I have very little accommodation.

Eye placement is a little sensitive.

I did not wear glasses.

In these dull conditions and with old eyes I found the magnification too low for details of gulls and crows flying around at 100 metres. However, the field is so large the birds stayed in the field a long time with no panning.

There are I think two uncoated surfaces each side with the other surfaces multicoated with varying colours.

For some reason the left to right view seems sharp almost edge to edge, although up and down things are not sharp far from centre.
Henry may have an explanation.

For some reason I prefer the Foton 5x25 binocular when I want a 12 degree plus field. This binocular is super sharp.

I really need to try the Komz 6x24 in bright conditions.

It is fine binocular.

Regards,
B.
 

Binocollector

Well-known member
Germany
For a good example of a flat field binocular eyepiece with enough straightforward pincushion to completely correct AMD check out the older Canon IS models as well as the newer 32mm models.
I wonder if the old non-IS Canon 8x32WP is similar. I read once that it has an Erfle-design ocular. It is very well corrected for field curvature but I'd have to check for pincushion again and whether it has the "moustache-distortion". It ranks among my favourite flat-field designs. Unfortunately it has no p-coatings. Still a nice bino, pretty sharp, flat field and almost no visible CA for my eyes.
I wish, Canon would make something like that again and not completey focus only on IS.
Considering the wide angles -- I prefer a "classic" high pincushion distortion like in the "miniature bino" (it isn't really all that small in fact) 6x25. For panning and scanning it feels the most "civilized". Kowa BDII and Komz 6x24 have way better eye relief however.
 

kimmik

Well-known member
United Kingdom
The result is low AMD across most of the field reversing to high AMD near the field edge.

Maybe a little inaccurate to say AMD reverses, it just progressively increases as you approach the edge, and moustache is the result only if the increasing AMD is more rapid near the edge than midway.

If the increasing AMD was consistent, then you get simple pincushion or perfect straight line.

Agree with all else though.
 

henry link

Well-known member
Yes, it would be better to say that AMD remains near zero over most of the field as the increasing pincushion keeps it in check, then the AMD blossoms near the edge after the pincushion reverses.
 

Binastro

Well-known member
The Komz 6x24 here has uncoated eyelens rear surfaces.
That is next to the eye.
I am not sure if there is one other uncoated surface.

However, despite the generally good multicoatings the Komz 6x24 is dimmer than the Leica BA 8x32.
As the Komz seems very clean inside, I suspect that the glass used is less transparent.

It may be that some leaded glass is used.

I am not sure if the BA has any leaded glass.

B.
 

Troubador

Moderator
Staff member
Supporter
Going back to Tenex's excellent introduction to this topic, here are the reasons why I favour wide fields of view for much of my bino use. The remaining part of my bino use consists of close-focus work which is an entirely different topic.

Bear in mind that my binocular use is mostly among the islands off the west coast of Scotland.

A wide field of view aids rapid scanning of the sea to find birds on the water and also birds such as mergansers and divers re-surfacing after diving below it, as well as scanning for signs of dolphins, porpoise, basking shark and otters. It also aids rapid scanning of the seaweed fringes around rocks, skerries and islets where otters forage. Above the sea there are big skyscapes with possibilites of Sea and Golden Eagles not to mention Peregrines, and over land one could add Hen Harrier and Merlin to this list.

In addition, wide fov can aid observations at short distances too, for example when small birds are flitting from bush to nearby bush or from rock to heather nearby, a wider fov is a big advantage in getting a glimpse of these birds despite their unpredictable directions of flight.

Similarly, capturing a look and nearby butterflies, dragonflies and moths in flight, is made easier with a wider field of view.

Summing up I simply find a wide field of view has definite practical advantages for my kind of bino use and I haven't even mentioned the pleasure of capturing wide views of coasts, islands, sea and sky under sunny or even stormy skies.

Lee
 

William Lewis

Wishing birdwatching paid the bills.
United Kingdom
I
Notice that the distortion in the Komz and the Kowa is not straightforward pincushion. It's mustache distortion, caused by pincushion that increases across the inner part of the field in the normal manner, but then reverses in the outer part giving a line near the field edge the appearance of a handlebar mustache. The result is low AMD across most of the field reversing to high AMD near the field edge.

The conclusions reached in the thread "Binocular Evolution II: Distortion and Curvature" about a supposed relationship between the correction of field curvature and distortion were simply incorrect. There is no relationship between the type and amount of rectilinear or angular magnification distortion and field curvature. For a good example of a flat field binocular eyepiece with enough straightforward pincushion to completely correct AMD check out the older Canon IS models as well as the newer 32mm models. To find eyepieces with even more pincushion combined with well corrected field curvature see the Televue Panoptic and naglers
Yes I think the photo through the srga highlighted this, lots of field curvature and blurry edges and a fair amount of pincushion distortion!
 

henry link

Well-known member
Yes I think the photo through the srga highlighted this, lots of field curvature and blurry edges and a fair amount of pincushion distortion!
It's pure coincidence that field curvature and pincushion distortion happen to be present together in that binocular. It doesn't have to be that way at all.

Check out the first part of my review of the Canon 10x32 IS below which deals with its distortion profile and off-axis corrections. What you see is a binocular with enough straightforward pincushion to achieve near zero AMD across the entire field combined with superb corrections of field curvature and off-axis astigmatism.

 

Binocollector

Well-known member
Germany
I think I need to take another few looks through all my flat-field binos now, to check which ones have pincushion distortion. But I guess most of them, otherwise they'd all have a rolling-ball effect.
 

tenex

reality-based
The conclusions reached in the thread "Binocular Evolution II: Distortion and Curvature" about a supposed relationship between the correction of field curvature and distortion were simply incorrect. There is no relationship between the type and amount of rectilinear or angular magnification distortion and field curvature. For a good example of a flat field binocular eyepiece with enough straightforward pincushion to completely correct AMD check out the older Canon IS models as well as the newer 32mm models. To find eyepieces with even more pincushion combined with well corrected field curvature see the Televue Panoptics and Naglers.
It would have been nice to hear this earlier. I don't have experience with a wide enough variety of eyepieces, so we futzed around with hypotheticals for quite some time over this.

Notice that the distortion in the Komz and the Kowa is not straightforward pincushion. It's mustache distortion, caused by pincushion that increases across the inner part of the field in the normal manner, but then reverses in the outer part giving a line near the field edge the appearance of a handlebar mustache. The result is low AMD across most of the field reversing to high AMD near the field edge.
The question that inspired that other thread (and lingers for me now) was: if such complex distortion is actually deliberate, rather than just tending to be a consequence of field-flattening, why does it seem desirable to engineer?
 

kimmik

Well-known member
United Kingdom
The nuance here, is that distortion is both deliberate, as well as accidental. Controlling another aberration may have unwanted effect on distortion, and it may not be uniform.

I don't think Henry was suggesting that complex distortion was a design goal, more a design limitation to satisfy other goals.
 

Binocollector

Well-known member
Germany
The question that inspired that other thread (and lingers for me now) was: if such complex distortion is actually deliberate, rather than just tending to be a consequence of field-flattening, why does it seem desirable to engineer?
The Komz and the Kowa do not have a flat field however. But both have "moustache"-distortion. So it must be caused by something else.
 

Troubador

Moderator
Staff member
Supporter
The question that inspired that other thread (and lingers for me now) was: if such complex distortion is actually deliberate, rather than just tending to be a consequence of field-flattening, why does it seem desirable to engineer?

I don't think Henry was suggesting that complex distortion was a design goal, more a design limitation to satisfy other goals.
My understanding is that it is not possible to simultaneously control all distortions/aberrations, because as you improve one, you make another worse, so it is not so much that the remaining distortions were considered 'desirable' by the engineer, more a case of these distortions being the inevitable and unavoidable consequences of other improvements that were given a higher priority.

If I am mistaken I am very willing to be corrected.

Lee
 

PeterPS

MEMBER
Field flattening and rectilinear distortion indeed are two different things. Concerning the latter, there are several design options: 1) insignificant rectilinear distortion, the downside being that the view may be affected by "rolling ball" effect (for example Swaro EL); 2) significant pincushion distortion to avoid rolling ball, but then the bino may have a "rolling bowl" effect, especially for wide field binos (such as is the case of Zeiss FL 7x42); and 3) mustache distortion to keep both rolling ball and rolling bowl under partial control especially for super wide-angle binos (for example, Kowa and Komz binos mentioned in this thread). In sum, while there is no correlation between field flattening and rectilinear distortion as design goals, there is at least a partial correlation between the latter and the size of the field of view.
 
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Binocollector

Well-known member
Germany
Rather interesting discussion. I just did a little more comparisons between my "skeleton bino", 6x25, 11.5° and the Komz 6x24. When looking through both they seem to have the same FoV -- the "skeleton bino" maybe being a tad wider.
To my eyes the "skeleton" J-B93 bino shows the perfect panning behaviour when it comes to the pincushion distortion -- just enough to completely eliminate rolling ball and not have "bowl" effect.
While the Komz is not as comfy to me when using.
The "skeleton" bino however has a far less sophisticated ocular design. I am not even sure how many lenses there might be, considering how short it is.
The Komz, I am pretty sure, has 5 lenses in the ocular -- at least the very similar 8x30 Komz has 5 lenses because it was even advertised as such when being sold by 3rd parties and labeled for "Bresser" or "Revue". It says "5-Linser" (5 lenses) on the bino itself.
So here is the thing though. I am beginning to think that it is just my eyes that perfectly harmonize with the "skeleton" bino more than with the Komz because I did a little "experiment" and put the lens of my smartphone camera on the ocular of the 6x25, "skeleton" and then scanned the scenery through the living room window -- and when looking at the smartphone screen I could see a distinct bowl-distortion.
Now the question is of course how much distortion does the wide angle smartphone camera lens have? Does its distortion ad more pincushion so the "skeleton" bino begins to show bowl distortion which it doesn't when I actually use it?
But the Komz on the other hand had an almost perfect panning behaviour when looking at the smartphone display.
So I guess it is my eyes that harmonize better with a "standard" large pincushion distortion in EWA binos than with the "mustache" distortion which to my eyes looks like barrel distortion.
img0kre47.jpg
 
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William Lewis

Wishing birdwatching paid the bills.
United Kingdom
Rather interesting discussion. I just did a little more comparisons between my "skeleton bino", 6x25, 11.5° and the Komz 6x24. When looking through both they seem to have the same FoV -- the "skeleton bino" maybe being a tad wider.
To my eyes the "skeleton" J-B93 bino shows the perfect panning behaviour when it comes to the pincushion distortion -- just enough to completely eliminate rolling ball and not have "bowl" effect.
While the Komz is not as comfy to me when using.
The "skeleton" bino however has a far less sophisticated ocular design. I am not even sure how many lenses there might be, considering how short it is.
The Komz, I am pretty sure, has 5 lenses in the ocular -- at least the very similar 8x30 Komz has 5 lenses because it was even advertised as such when being sold by 3rd parties and labeled for "Bresser" or "Revue". It says "5-Linser" (5 lenses) on the bino itself.
So here is the thing though. I am beginning to think that it is just my eyes that perfectly harmonize with the "skeleton" bino more than with the Komz because I did a little "experiment" and put the lens of my smartphone camera on the ocular and then scanned the scenery through the living room window -- and when looking at the smartphone screen I could see a distinct bowl-distortion.
Now the question is of course how much distortion does the wide angle smartphone camera lens have? Does its distortion ad more pincushion so the "skeleton" bino begins to show bowl distortion which it doesn't when I actually use it?
But the Komz on the other hand had an almost perfect panning behaviour when looking at the smartphone display.
So I guess it is my eyes that harmonize better with a "standard" large pincushion distortion in EWA binos than with the "mustache" distortion which to my eyes looks like barrel distortion.
img0kre47.jpg
You can get a good idea of the Fov by shining a phone torch through the eye piece of each and seeing how wide the projected circles of light are on a wall or similar.
 

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