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PFOV concept (1 Viewer)

Very interesting. Im glad to hear there's more than one manufacturer of photochromatic. These appear to be non-prescription sunglasses? The stuff I use is called "transition", and it may have more neutral color bias, ... at least the gray ones. This is my second pair and the responsiveness has improved a great deal. Take a look. You might want to use eyeglasses while birding after all. ;)
http://en-us.transitions.com/en/default.aspx?gclid=CMnvndbL360CFQ5lhwodyCoHCQ

Thanks for starting this thread //LS. :t:

Ed

Ed:
I like sunglasses with the plastic frames, with curved lenses. :cool: Then I find
the eyerelief is too much, and so they don't work so well for me, with binoculars.

Jerry
 
AFAIK, there are only three manufacturers of organic photochromic spectacle lenses.
These are Transitions, who market their brand directly to consumers although they are not making the very lenses, Hoya and Rodenstock who are optical lens factories.

For silicate lenses, I only know of Schott, but there may be others as well.
Typically, the newer generations of organic lenses are very fast in their response and have a wide range of activation, from almost clear to a full 80 or 85 percent absorption.
The silicate lenses are typically slower and have a narrower range of activation.

The effect is triggered by UV radiation and they will not be very dark when driving a car unless it's a convertible with the roof down. Outside, they will activate, but in overcast weather they will be disproportionally dark because of the greater UV portion of the total light amount.
They will also be darker in colder weather because low temperature will delay the "bleaching" of the lens caused by white light.
The degree of activation is decided by the amount of UV radiation for darkening, the amount of white light for bleaching and the temperature.

Mine were Hoya lenses, and while looking neutral grey they peaked some colors quite a bit towards reddish.

Prescription lenses can be had without dioptric power and the price would be the same as for lenses with power.

//L
 
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... Typically, the newer generations of organic lenses are very fast in their response and have a wide range of activation, from almost clear to a full 80 or 85 percent absorption.

That's the kind I like, Hoya. There is a valid reason for attenuating high intensity blue, so that may be part of the reason for a red bias. Swarovski also seems to do this with their transmission curves, and I'm sure they could do otherwise if they wanted to.

Take note, Jerry, plastic frames with curved lenses are strictly passé! Next you'll tell me they have to be mirrored. :'D

Ed
 
That's the kind I like, Hoya. There is a valid reason for attenuating high intensity blue, so that may be part of the reason for a red bias. Swarovski also seems to do this with their transmission curves, and I'm sure they could do otherwise if they wanted to.

Take note, Jerry, plastic frames with curved lenses are strictly passé! Next you'll tell me they have to be mirrored. :'D

Ed

Ed:
I wear sunglasses for protection against the sun's rays, and I do not care
about looks, but need styles with wide temples.
I am outdoors a lot, and have to take precautions, as I have had some skin cancer, in that area.
Probably more than you wanted to know, but just a reminder here for everyone here, to take precautions, and protect yourself.

Jerry
 
Jerry,

Sorry to hear that. Forgive me please, I was just joking.

Ed
PS. I'm a three time cancer survivor myself.
 
Ed:
I wear sunglasses for protection against the sun's rays, and I do not care
about looks, but need styles with wide temples.
I am outdoors a lot, and have to take precautions, as I have had some skin cancer, in that area.
Probably more than you wanted to know, but just a reminder here for everyone here, to take precautions, and protect yourself.

Jerry

Me too Jerry. I know what you mean.
 
My lenses are rather large, not the tiny lenses that are currently in style. Makes me look like a nerd, but there is plenty of surface area for even the largest eye cups.

Bruce
 
Back on topic with new images showing a simple experiment.
This explanation of PFOV is not optical, but very much shows what happens in the visual field.

The images would clearly show it, but if you want to make the experiment it only takes a paper tube and a round cardboard roundel with a hole in the center.
Of course there's no lenses or magnification involved, so differences in AFOV and PFOV will solely depend on the diameter of the tube and the hole.

The outer, open end of the tube is the angular field. If you look through the tube before attaching the roundel, you will see a certain portion or cut-out of the reality in life-size, and the walls of the tube will hide the rest.
A wider and/or shorter tube will expand the FOV.

The hole's diameter does NOT correspond to the exit pupil size or ocular lens size, but to the eye relief.
If the hole is smaller, you will need to get closer to see the whole FOV, but if it is bigger, you can hold the tube further away.

In the first image, the roundel barely hides the walls of the tube. If held closer, like in the second image, you will see more of the walls.
In addition, the outer diameter of the roundel will occupy more of your visual field, thus decreasing the free angle of sight.
Here, it is obvious that the angular size of the obscuration from the fieldstop to the outer edge of the roundel is greater when the bins/tube are held too close.

The third image shows what happens when you're too far from the hole - you will of course not see as much of the field.

The fourth image (upper right) shows a larger diameter tube with a smaller hole. This corresponds to a larger FOV with a shorter eye relief compared to the first ("Ideal") image. Pretty much of the visual field gets obscured by the large diameter of the roundel, but the image or FOV portion is larger.

The last image (lower right) shows that if you use a cone-shaped tube, nothing happens with the FOV.
Surprisingly little, but still some, happens with the free angle of sight. This is because the tiny eye relief means than the ocular end of the cone occupies much of the visual field.
Image #4 and #5 should explain why Frank's two porros, although similar, feel different. I believe it's a matter of external differences.

Somebody put the question if binocular's makers shouldn't make separate models for spectacle wearers and non-bespectabled.
Undeniably, many models seem to be much of compromise, and the way to handle the downsides of sufficient eye relief for them, is to use twist-up eyecups.
That is not the perfect way to do it, since they obscure much of the visual field.

//L
 

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//LS,

Just read this a second ago. At first blush it seems very clever and makes a lot of intuitive sense, but it will take me a while to satisfy myself that it generalizes to a universal telescope interface.

In any event, it's quite inventive and very interesting. Congratulations! :t:

There are relevant perceptual phenomena that can also be demonstrated with your model, which may help to explain some subjective reports on this and earlier threads.

Good thinking!

Ed
 
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I have been working on a somewhat different approach shown in the preliminary drawing below. But I'm not sure where it's leading. I had something in mind. Wait ... ;)

Ed
 

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The scaling may be off a bit, but the geometry suggests (a) that the bulk of the binocular is not in the visible field, even a Porro, and (2) an appreciable amount of unmagnified information within the 120º overlap area of the retina can enter though the corrective eyeglasses beyond the annulus.

For the most part, unmagnified information beyond the eyeglasses themselves probably projects onto the 30º monocular fields on either side. This will vary with the eyeglass diameter. Finally, because of the steep angles involved, very little size change or fore-aft movement can result in a large change in how the full field appears. Hence, each individual may take a bit of fitting before everything works just right.

I'm still fascinated by whether or how the brain integrates magnified and unmagnified images in the overlap area.

Ed
 
While I find this thread quite interesting, I find most of the diagrams quite optimistic and over simplified. I took a pair of 8x36 Bushnell Legend Ultra HD's and set them up on a tripod at a distance of 10 ft from a measuring tape. With the eyecups collapsed and my glasses on I could see a width of 17", and glancing to the side it was 68" from the left fieldstop to where the obstuction of the eyecup and bino ended. So in this test I am seeing the 426 ft TFOV of the bino but it is obscured by an additional 1700 ft TFOV on each side before the peripheral vision is unobstructed. Handholding the bino would add even more of an obstucted FOV to the sides than the 1700 ft.

While I would not say that I have an enhanced or greater perceived FOV with glasses, I would acknowledge that with glasses I can see more of the outer peripheral. Perhaps a better term than PFOV in my mind might be spatial awareness.

Tom
 
The scaling may be off a bit, but the geometry suggests (a) that the bulk of the binocular is not in the visible field, even a Porro, and (2) an appreciable amount of unmagnified information within the 120º overlap area of the retina can enter though the corrective eyeglasses beyond the annulus.

For the most part, unmagnified information beyond the eyeglasses themselves probably projects onto the 30º monocular fields on either side. This will vary with the eyeglass diameter. Finally, because of the steep angles involved, very little size change or fore-aft movement can result in a large change in how the full field appears. Hence, each individual may take a bit of fitting before everything works just right.

I'm still fascinated by whether or how the brain integrates magnified and unmagnified images in the overlap area.

Ed

Hm, tricky one...
Your drawings show a front view towards the eye and a view from the side.
Mine have only shown the view from above, where the visual field expands towards right and left. And, yeah, a cycloptic view to be correct, where no nose is in the way and left and right eye are made one.

At the moment, I have no porro in my possession, but frankly I'd guess that the prism housings + the hands will intrude on those, the lateral parts of the visual field.
More so with shorter physical length of the oculars, or with longer eye relief where the diameter of the eyepiece will not hide them.
But I may be wrong, it has occurred before.

The spectacle lenses' width is of interest only for the lateral parts of the visual field. But nobody will receive a focused image of the medial parts of the bins, either because of the short distance (1" to 2") or because they are way out of the eye's zone of sharpness when you look through the bins.
The zone of sharp vision sits in the 2 degrees absolute center of the visual field.

The height of the spectacle lenses might be of significance should they allow to glance upwards when the bins are held in place, provided their ocular diameter is not too large. When looking straight forward, the peripheral parts of the lenses carry no additional information that is useful for the sense of vision.
Extremely large lenses would however be hard to wear, and grease from the eyebrows would deposit on them immediately.

Possibly, a thick spectacle frame might pose some noticeable intrusion. It has happened to me, but it was actually in the very image after being pushed-up by the bins.

//L
 
This is an interesting optical illusion that I've seen a few times. It's very vivid.

I think the issue here is where the final aperature that just matches the vignetting aperture.

I've even seen this effect on "narrow" field bin with pop up eyecups. If you set the eyecups just right (just about vignetting the FOV) it appeared a lot bigger.

I think the issue here is where the final aperature that just matches the vignetting aperture.

Eureka II!
 
...I've even seen this effect on "narrow" field bin with pop up eyecups. If you set the eyecups just right (just about vignetting the FOV) it appeared a lot bigger.

Let's share in the joy.

Where did Kevin's post(s) come from, what is the "effect," and what appears a lot bigger?

And what does this have to do with using glasses and the so-called perceived FOV?
 
Hm, tricky one...
Your drawings show a front view towards the eye and a view from the side.
Mine have only shown the view from above, where the visual field expands towards right and left. And, yeah, a cycloptic view to be correct, where no nose is in the way and left and right eye are made one.

At the moment, I have no porro in my possession, but frankly I'd guess that the prism housings + the hands will intrude on those, the lateral parts of the visual field.
More so with shorter physical length of the oculars, or with longer eye relief where the diameter of the eyepiece will not hide them.
But I may be wrong, it has occurred before.

The spectacle lenses' width is of interest only for the lateral parts of the visual field. But nobody will receive a focused image of the medial parts of the bins, either because of the short distance (1" to 2") or because they are way out of the eye's zone of sharpness when you look through the bins.
The zone of sharp vision sits in the 2 degrees absolute center of the visual field.

The height of the spectacle lenses might be of significance should they allow to glance upwards when the bins are held in place, provided their ocular diameter is not too large. When looking straight forward, the peripheral parts of the lenses carry no additional information that is useful for the sense of vision.
Extremely large lenses would however be hard to wear, and grease from the eyebrows would deposit on them immediately.

Possibly, a thick spectacle frame might pose some noticeable intrusion. It has happened to me, but it was actually in the very image after being pushed-up by the bins.

//L

//L

I was using a preliminary drawing with unconfirmed lengths and distances, so it may have been premature. Also, I was thinking about lateral pencils of light rather than those from above or below, but that's hard to depict in a 2-D drawing at my level of skill.

Not sure if we're on the same glide path here, but the entire retina receives focused visual images, not just the central 2º where fine scene detail is examined. (Otherwise, I guess, it really wouldn't be there.) Moving out from the center, focus demand becomes less critical because visual resolution diminishes progressively. But there is measurable resolution capability over the entire retina that relates to the neural substate of the retinal cells. This is why folks who lose central vision due to disease can somewhat rely on magnified peripheral vision.

As shown on my earlier drawings, the retinal projection of a typical 60º binocular still leaves a great deal of retinal area unstimulated in the 120º overlap zone, which is the area used for steropsis. Naturally, with the binoculars directly in front of the pupil it would not be possible to bring this to the fovea unmagnified, but the area is still being stimulated by images and somehow merged or fused into the observer's perceptual field. Lateral/vertical pencils coming from beyond the eyeglass frame probably project mostly onto monocular areas of each eye, and may contribute to the perceptual field as they do in normal vision, i.e., by providing monocular perspective or motion cues.

Cheers,
Ed
 
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//L
Not sure if we're on the same glide path here, but the entire retina receives focused visual images, not just the central 2º where fine scene detail is examined. (Otherwise, I guess, it really wouldn't be there.) Moving out from the center, focus demand becomes less critical because visual resolution diminishes progressively. But there is measurable resolution capability over the entire retina that relates to the neural substate of the retinal cells. This is why folks who lose central vision due to disease can somewhat rely on magnified peripheral vision.

The visual acuity decreases very fast outside the 2 central degrees.
Yes, there is measurable visual acuity, down to counting fingers at a certain distance. I think the use of the peripheral retina is somewhat an effect of learning how to put together a patch-work of visual cues.
This means it takes quite a lot of time even if the letter or symbol is of the size of 1/20 (VA= 0.05).
But there is a swedish ophtalmology professor who has succeeded to raise the visual aquity somewhat by means of very special optics, intended for excentric fixation. His name is Jörgen Gustafsson.

I'm having serious doubt that the retina receives focused light in the periphery. I may be wrong, but I feel quite convinced about that.
We would never be able to be outside a sunny day. The sun would boil the retina in seconds. Even if the peripheral retina would be more robust than the fovea, it wouldn't withstand the burning glass effect.


As shown on my earlier drawings, the retinal projection of a typical 60º binocular still leaves a great deal of retinal area unstimulated in the 120º overlap zone, which is the area used for steropsis. Naturally, with the binoculars directly in front of the pupil it would not be possible to bring this to the fovea unmagnified, but the area is still being stimulated by images and somehow merged or fused into the observer's perceptual field. Lateral/vertical pencils coming from beyond the eyeglass frame probably project mostly onto monocular areas of each eye, and may contribute to the perceptual field as they do in normal vision, i.e., by providing monocular perspective or motion cues.

Cheers,
Ed

Yes, I remember your visual field map in your post #24. Making wide angle oculars is not an easy task, but it can be done.
I'm not quite sure, but the outer diameter of the oculars, or more precisely, the inner diameter of the rim, has to be located outside those 100+ degrees. The large diameter would leave little space for the nose unless your IPD is >72 mm.
The fieldstop would most likely be fuzzy.
Possibly more parallax would occur, at the extreme edges so that the FOV would appear not so round, but that's only my guess.

//L
 
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... I'm having serious doubt that the retina receives focused light in the periphery. I may be wrong, but I feel quite convinced about that.
We would never be able to be outside a sunny day. The sun would boil the retina in seconds. Even if the peripheral retina would be more robust than the fovea, it wouldn't withstand the burning glass effect.

Full stop. Focusing an optical image over the retina is one thing, and having the neural apparatus to resolve fine detail in a particular retinal area is another. But why on earth would the sun "boil the [peripheral] retina in seconds" if images were focused there but not at the fovea? I take it you actually believe this to be true — with or without glasses. Good grief!

Needless to say there is quite a distance between our understanding of things. BTW, I'm the one who introduced the word "perception" into the discussion on post #12 after Kevin's comment on post #8. I'm a perception guy. :king:

Best regards,
Ed
 
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