Two Mechanisms of Vision: Ambient Vision and Focal Vision (2 Viewers)

[Hermann]

Why you should not pan with your binoculars
[snip]
Our oculomotor system and its controller nerve called 3rd cranial nerve are extremely precious. We should not endanger them by forcing our eyes into an involuntary, rapid and repetitive movement. Panning with binoculars can result in many symptoms such as blurred or shaky vision, difficulty with balance, and the sensation that surroundings are moving (oscillopsia).

I'm sorry, Omid, but ... "We should not endanger [my emphasis] them by forcing our eyes into an involuntagry, rapid and repititive movement." Endanger them? Isn't that perhaps too strong a term? I've been birding for more than 40 years now, and the way I bird involves a lot of panning on many occasions, both with binoculars as well as with scopes at high magnification. AFAIK I suffered no serious after effects of panning, sometimes for hours on end. No "blurred or shaky vision, difficulty with balance, and the sensation that surroundings are moving." And I never heard a birder complain about such problems.

I agree panning can be tiring, sometimes even very tiring if "nothing happens" (or the bird you're trying to find doesn't turn up ... ), but most people would take a break then, have a cup of coffee and a chat. And then go back to panning.

I've got the feeling this is a case where the theory says one thing. But what's happening in real life may be quite different.

Hermann

 

[Holger Merlitz]

If I understand correctly, then the warning issued by this doctor in his video addressed patients with neurological problems, who are planning to apply these little animations as part of their training procedure. It would probably be a stretch to extend this warning to the normal binocular user. But sure, panning a binocular is a somewhat unusual visual experience, and whoever feels unwell after using his binoculars should be cautious.

Cheers,
Holger

 

[Canip]

So, if I may repeat my question:
How do you follow a bird in flight with binoculars if you shouldn‘t pan?

I have been following birds in flight with my binoculars for many years now, esp. birds with a „predictable flight pattern“, such as birds of prey, storks, herons etc.

I fully understand what you say and what you mean by the symptoms triggered by panning. Everyone who has ever been panning for extended periods has probably experienced physiological effects. That‘s why you rest your eyes from time to time when using binoculars for longer periods of time.

I just haven’t figured out a way to follow birds in flight - necessary sometimes even for identifying species etc - without panning. Maybe you know how it’s done?

Sorry, I did indeed miss or misinterpret Omid‘s explanation of the difference between „tracking“ (folllowing a bird in flight) and „panning“.

I think that „tracking“ a bird in flight against a landscape background (possibly leading to intermittent saccadic movements as the background is not homogenous) may cause different effects than tracking a bird against a clear sky background. Or not?

 

[Holger Merlitz]

Sorry, I did indeed miss or misinterpret Omid‘s explanation of the difference between „tracking“ (folllowing a bird in flight) and „panning“.

I think that „tracking“ a bird in flight against a landscape background (possibly leading to intermittent saccadic movements as the background is not homogenous) may cause different effects than tracking a bird against a clear sky background. Or not?

Hi Canip,

I would guess that the eyes would stay fixated on the bird in both cases, ignoring whatever happens in the background. The only difference would be that this process of actively ignoring the background noise is much easier with a clear sky background where there is nothing left to do for the filter process. In any case, our visual information processing system is an extremely powerful tool when it comes to the real-time interpretation of image data, and it is able to separate different motion patterns that occur simultaneously. This is obviously the result of millions of years of evolution in a hostile environment in which it was of the essence to recognize danger (or prey) before it was too late.

Cheers,
Holger

 

[Omid]

I got dizzy from watching (the interesting) first video, in a way quite the same dizzying effect i had when using an NL Pure, with my Leica’s I never experience this. Is there maybe a relation?

Yes, there is. Binoculars with extra-large field of view will trigger multiple unpleasant symptoms if used handheld by a human being who lives on the surface of the earth.

One aspect (dizziness caused by panning) we have discussed already. Several other factors, such as the "false visual ground" which becomes more visible in the lower portion of field of view, we have not discussed yet.

Have you paid attention to the ground you are standing on when looking through your wide-angle NL Pure binoculars? Keep your binoculars strictly horizonal and look down at the ground; how does the ground surface look? Then tilt your binoculars up or down a few degrees, how does the ground change?

When "down" and "up" as registered by your Ambient Visual system are not consistent with the direction of gravity as registered by your vestibular organ in your inner ear, you will become dizzy and seasick. The effect of a conflict between visual "horizonal" and gravitational "horizontal" has been studied extensively by prominent visual psychologists such as the late Ian Howard (in Canada), along with Sheldon Ebenholtz and Herschel Liebowitz (in the USA).

 

[Omid]

I would guess that the eyes would stay fixated on the bird in both cases, ignoring whatever happens in the background. The only difference would be that this process of actively ignoring the background noise is much easier with a clear sky background where there is nothing left to do for the filter process. In any case, our visual information processing system is an extremely powerful tool when it comes to the real-time interpretation of image data, and it is able to separate different motion patterns that occur simultaneously. This is obviously the result of millions of years of evolution in a hostile environment in which it was of the essence to recognize danger (or prey) before it was too late.

Hello Holger,

I agree with your thoughts: it is probably easier to filter out the distracting background when there is none. It would be interesting to think about the "bird tracking" problem in the context of feedback control with and without binoculars:

Without binoculars, the visual system seems to rotate both head and eyes to track a moving object. I am not sure how exactly the brain decides which body parts must rotate by how much to maintain an object's image on the fovea (two nested control loops? That's not very effective, they will conflict unless there is some form of coordination). With binoculars, rotating the {head + binoculars} will create a disproportionate effect due to optical magnification further complicating the problem. My guess is that "eye rotation" is inhibited in this case but I have no proof.

The evolution of eye movements and their function in animals that have a rotatable "head" and further have two "rotatable eyes" inside said rotatable head is a truly fascinating subject!

-Omid

 

[NatureLover123]

Thank you for the highly interesting colloquium. We need more exchanges like this in the forum.

Our brains and vision is the result of millions (maybe billions) of years of dicing, birth, mutations, tests, failing (dying) and success (surviving). The performance of our brains will always have room for improvement, but I think we are able now to invent a tool that enhances the human vision to something, that allows us to see and experience more as the current state of evolution allows.

If our early ancestors had had access to binoculars, we would probably have discovered America much earlier, we would already know the nature of dark matter, and would also have discovered the second Earth. 😂

 

[Maljunulo]

It seems to be believed that light-sensitive cells were around earlier than the Cambrian. Euglena has a light-sensitive spot.

The image-forming eye seems to have been “invented” by cephalopods and vertebrates independently. (?)

Trilobites had compound eyes, and predated insects, but the idea never caught on with vertebrates.

This is all from a quick trip around the internet, and I would be interested (as always) to hear what someone who knows what they are talking about has to say, to expand on it.

 

[Hermann]

Binoculars with extra-large field of view will trigger multiple unpleasant symptoms if used handheld by a human being who lives on the surface of the earth.

That's an interesting point. I find binoculars with a very large field of view more "tiring" than binoculars with a narrower field of view, especially when using them for long periods of time. An AFOV of ~60 degrees still works pretty well for me. Larger fields of view not so much. Interestingly Köhler comes to a somewhat similar conclusion, he draws the line at 70 degrees and remarks, "dass sich bei Feldstechern größere Sehfelder als 70 Grad nicht so recht eingeführt haben". (Quoted in Hans T. Seeger (1989): Feldstecher. Ferngläser im Wandel der Zeit. Bresser-Optik, Borken, p. 128.)

Hermann

 

[Hermann]

I think that „tracking“ a bird in flight against a landscape background (possibly leading to intermittent saccadic movements as the background is not homogenous) may cause different effects than tracking a bird against a clear sky background. Or not?

I'm not sure. If I'm tracking a bird (or whatever) against a landscape background, I'm still solely focused on the "target", I don't "see" the background. But of course this becomes easier if the background is uniform, like the sky. By contrast, if I'm panning the landscape, for instance to find a bird, my focus is different: I try to look at everything within the FOV in order to find my target, so I pay attention to everything I see.

Hermann

 

[Maljunulo]

I'm not sure. If I'm tracking a bird (or whatever) against a landscape background, I'm still solely focused on the "target", I don't "see" the background. But of course this becomes easier if the background is uniform, like the sky. By contrast, if I'm panning the landscape, for instance to find a bird, my focus is different: I try to look at everything within the FOV in order to find my target, so I pay attention to everything I see.

Hermann

You may not notice the background, due to some brain magic, but I would bet that you do see it.

 

[Holger Merlitz]

That's an interesting point. I find binoculars with a very large field of view more "tiring" than binoculars with a narrower field of view, especially when using them for long periods of time. An AFOV of ~60 degrees still works pretty well for me. Larger fields of view not so much. Interestingly Köhler comes to a somewhat similar conclusion, he draws the line at 70 degrees and remarks, "dass sich bei Feldstechern größere Sehfelder als 70 Grad nicht so recht eingeführt haben". (Quoted in Hans T. Seeger (1989): Feldstecher. Ferngläser im Wandel der Zeit. Bresser-Optik, Borken, p. 128.)

Hermann

The design of binoculars with very wide AFOV requires care, since they trigger lots of receptors in the peripheral part of the visual field. Our eye is particularly sensitive to motion in these outer areas, no doubt a protective measure to quickly react to something approaching from the side. I am not surprised to learn that once something goes wrong here with the image, the observer will feel uneasy. I want to add that my Nikon 10x50 WX with 85° field is a pleasure to use and I never felt dizzy observing with them or panning them.

Cheers,
Holger

 

[Hermann]

You may not notice the background, due to some brain magic, but I would bet that you do see it.

No disagreement from me. I meant that I don't consciously perceive the background, that's why I put the "see" in inverted commas. So I see it - but I don't see it.

Hermann

 

[Charlie Yardbird]

Hello Holger,
I agree with your thoughts: it is probably easier to filter out the distracting background when there is none. It would be interesting to think about the "bird tracking" problem in the context of feedback control with and without binoculars:

Without binoculars, the visual system seems to rotate both head and eyes to track a moving object. I am not sure how exactly the brain decides which body parts must rotate by how much to maintain an object's image on the fovea (two nested control loops? That's not very effective, they will conflict unless there is some form of coordination). With binoculars, rotating the {head + binoculars} will create a disproportionate effect due to optical magnification further complicating the problem. My guess is that "eye rotation" is inhibited in this case but I have no proof.

The evolution of eye movements and their function in animals that have a rotatable "head" and further have two "rotatable eyes" inside said rotatable head is a truly fascinating subject! -Omid

I wonder if it would help the brain to have a high contrast dot at the center of the lens, or even a crosshair, which might make it easier for the brain/muscles to keep the fovea in the center of the lens as the lens is moved.

 

[NatureLover123]

Interesting idea with the dot or crosshair. But it should be mechanically disableable if not needed.

 

[Charlie Yardbird]

Dependence of Visual Acuity on Illuminance:
At low light levels, contrast sensitivity of the eye is approximately 8% and maximum resolution is approximately 6 cycles per degree. As ambient light levels increase, the eye's contrast sensitivity improves, and it can now detect contrasts as low as 0.5% for spatial frequencies in the range of 5 to 10 cycles per degree. Note that for photopic (daylight) viewing, sensitivity to contrast diminishes both for high and low spatial frequencies. (This last little detail is not anticipated by either K-L or B theories discussed in your paper. But then again, those researchers were mainly concerned with smallest possible objects and also with low light conditions. So, it's OK. I don't blame them.)
SNIP

Would you please give a reference explaining "spatial frequencies," which seem to be measured in units of "cycles per degree?" The units in the x & y axes of the graph are also Greek to me, how do they relate to the qualities discussed in your associated paragraphs?

 

[Omid]

I wonder if it would help the brain to have a high contrast dot at the center of the lens, or even a crosshair, which might make it easier for the brain/muscles to keep the fovea in the center of the lens as the lens is moved.

Hi Charlie,

You are thinking along the right direction. Yes, in principle, having a high contrast red dot at the center of field of view will offer a "fixation target" to the eye and will nearly completely eliminate the onset of optokinetic nystagmus. This has been proved in a groundbreaking clinical trial commissioned by NASA and whose results were published in 1990.



In this study, Dr. Robert Stern (1937-2020, pictured above) and his colleagues subjected 45 healthy persons to a uniformly moving optical flow field and measured their gastric myoelectric activity to monitor motion sickness. The 45 subjects were randomly divided into the following three groups:

• a control group that observed the entire visual field with no fixation,
• a group that fixated on a central target, and
• a third group that had a visual field restricted to 15 deg.

The results showed that fixation greatly reduced nystagmus and slightly reduced vection (feeling of self-movement). The restricted visual field slightly reduced nystagmus and greatly reduced vection. Both of these manipulations significantly reduced symptoms of motion sickness and abnormal gastric myoelectric activity.

So, yes by offering a fixation target it should be possible to prevent optokinetic nystagmus while panning the binoculars. But it is not really useful to introduce an artificial fixation target for a number of reasons: if you are tracking a bird in flight, the bird itself acts as a fixation target, and we don't need the red dot. If you are panning across a wide scene to look for a bird, the red dot will help divert attention from the moving background image which contains the bird you are looking for!!

Thank you for paying careful attention to my posts. I'll get to your second question (post # 56) if I find time in the future.
-Omid

PS. Due to shortage of time, I haven't yet explained Item 2 in Post #38 where I said panning with binoculars to find wildlife is useless. There are fundamental biological reasons for this claim separate from the onset of optokinetic nystagmus. I invite the learned members of this glorious forum to figure out these reasons themselves based on the scientific facts about human vision that I have already provided in Posts #1 and #2

 

[Patudo]

panning with binoculars to find wildlife is useless.

I had not thought until now that anything not written by d***o could make me laugh so hard.

I want to add that my Nikon 10x50 WX with 85° field is a pleasure to use and I never felt dizzy observing with them or panning them.

Neither did I when I have observed with one, nor with other wide fields such as Swift #766 or Zeiss West 10x50. Hermann's point about a large FOV binocular being more tiring to use for long periods is interesting though - I can see how a larger FOV might result in more fatigue, as it feeds more info in magnified form to the brain. I also tend to find with a large FOV I move my eyes around the FOV more when searching, to make sure I've covered the entire FOV, which I suppose could lead to more fatigue if the image isn't very well corrected (as it is with the WX, which I also much prefer to use on a tripod) - whereas a smaller FOV everything is "there".

Having said all that, I would still prefer a wide field binocular provided it's not too large and heavy and has a reasonable sweet spot. The advantage in situational awareness that wide FOV gives is so useful that I would almost always want to have it.

 

[Andrew Rowlands]

Our oculomotor system and its controller nerve called 3rd cranial nerve are extremely precious. We should not endanger them by forcing our eyes into an involuntary, rapid and repetitive movement. Panning with binoculars can result in many symptoms such as blurred or shaky vision, difficulty with balance, and the sensation that surroundings are moving (oscillopsia).

Reads much like how vertigo feels.

I have positional vertigo that I try to avoid but I cannot trigger it by normal pan/scanning with an 8x32SE or Retrovid 7x35; never experienced it using other optics over the last several years either. In my pre-vertigo period, ~50 years of bino. owning and using, I never experienced anything like that - maybe because I grew up with anxiety/motion sickness and my inbuilt detector slows/stops my panning in the very early stages.

Not going to test it whilst sitting on a anti-clockwise spinning roundabout.

Ignoring easy, moving targets; in my usual locations my panning is relaxed, seemingly relying on brain detection spotting likely shapes, triggering brief stop/rewind moments where I check out the possible 'target' before continuing the sweep. Any difficult 'blobs', unconfirmed species might be revisited several times, often after a relocation closer, or for a better angle, esp. for contre-jour lighting.

I have used 2x binoculars that triggered something that might be associated with vertigo, or perhaps more likely - migraines. That's an odd speckled, starry 'overbright?' optical effect. This also happened to me once last year without me looking through any optics, or moving in a way/direction that might trigger vertigo, though mentally I was reviewing what I'd seen briefly a few seconds before.

 

[Holger Merlitz]

...

PS. Due to shortage of time, I haven't yet explained Item 2 in Post #38 where I said panning with binoculars to find wildlife is useless. There are fundamental biological reasons for this claim separate from the onset of optokinetic nystagmus. I invite the learned members of this glorious forum to figure out these reasons themselves based on the scientific facts about human vision that I have already provided in Posts #1 and #2

Hi Omid,

Still, these ideas must also be compared with daily life experience in the field. Panning is something we (have to) do all the time, and it more or less works out: You pan around, seem to find something interesting, stop panning, start observing. This is how it works and there is no real alternative to this approach if you don't know where exactly your next target will be. That is why we want to pay great attention to the design of the distortion curve of binoculars which are used for surveillance so that the panning becomes as pleasant as possible. Officers in the battle fields complained about the globe effect because its rolling motion distracted the soldier and made it difficult to identify real movements of objects in the field while panning. The combination of panning and target detection has always been an unavoidable necessity in binocular applications.

Cheers,
Holger