A Philosophical Question about Optics

[scat1134]

I'm a phd student at Oxford, working on the philosophy of perception. I would like to ask for people's help on a question of optics. This question arose when I was thinking about the following hypothesis:

Could everything look smaller to you than to me, without there being any behavioural difference between you and me?

The question of optics arose because I'm trying to evaluate this hypothesis by thinking about minimizing and magnifying lenses. Since I think there is an optical question here, I thought that a forum of optics experts could be very helpful.

Let me explain what I think the optical question is here.

Normally, when you put on magnifying lenses, two things happen: 1.) whatever you see before you looks larger than before, and 2.) the physical angle that you see in the world decreases (i.e. you see a smaller angle of stuff).

Similarly, when you put on minimizing lenses, I assume (though I haven't tried minimizing lenses), again two things happen: 1.) whatever you see before you looks smaller, and you come to see a wider physical angle than you did before (i.e you see a wider angle of stuff).

The question I'd love some help on is this. Are there optical lenses that can make the stuff you see before you look bigger/smaller, without affecting how much stuff you see, i.e. without affecting the physical angle that you see?

These would be optical lenses that did 1.) above without doing 2.). For instance, they would be lenses that reduced the apparent size of everything you see, without increasing your viewing angle. Or they would be lenses that increased the apparent size of everything you see, without decreasing your viewing angle.

What interests me about such lenses is that they would generate pure apparent size effects, without generating any effects on the size of viewing angle. They would, in effect, perform a perfect reduction of the size of the visual image, preserving all the proportions of the things in that visual image, and without making you see a wider angle of objects in the visual image.

Does anyone know whether lenses that meet this description exist? As I said, these lenses, I think, would not be standard magnifying/minimizing lenses, since the standard magnifying/minimizing lenses that I've come across have both effects: they alter apparent size, and also affect your viewing angle. So, in wanting to find lenses that have just the first effect alone, I realize that I may be asking about some fairly non-standard lenses.

I'd be extremely grateful for any feedback on whether such lenses do exist. Many thanks in advance for your help!

[Chris Ryser]

Professor Edwin Herbert Land...................the inventor of "Polaroid Cameras and many other optical items once made a atatement and also proved it.

If a lens filters out a certain color, you will not see this color when looking through that lens. Of course all other colors will look different when the object contain the filtered color.

However when continuing looking through that particular lens for a certain time, suddenly you will start seeing that filtered out color again and color will start looking normal again.

This Dr. Land's principle has been applied in optical lenses that are now called "Blue-Blocker" lenses. If you wear these lenses in glasses they will block out blue, which is so called fuzzy light, and you will not see the blue.
However the brain will adjust to it and let you see blue again which is not there at all.

These lenses also will provide a very high contrast perception and see better and clearer in a misty environment as well in snow and on the water or the road.

The brain having been cheated out of reality will compensdate for it.

Hope having given you an optical answer without having gone into the larger and smaller vision but it could be related.

[PAkev]

I think it has something to do with the color of fire engines:

Fire engines are red because newspapers are read too. 2 + 2 is four and four times three is 12. 12 inches is in a foot and a foot is also a ruler. Queen Mary was also a ruler and a big ship. This ship sailed on the sea and in the sea were big fish with big fins. People from Finland are also called Fins. A long time ago the Fins and Russians got in a war and the Fins burned all of Russia's crops and cities. As Russia was red, fire trucks were rushin so they just decided to also make fire trucks red.

Seriously, I think you answered your own question by identifying the corrective solution to the following vision problems.

Hyperopia (farsighted)...The existing focal point is too long so the magnification effect of a + lens brings the perceived (real) image forward of the existing focal point to correct the visual deficit.

Myopia (nearsighted)... The existing focal point is too short so the minification effect of a - lens brings the perceived (virtual) image beyond the existing focal point to correct the visual deficit.

Emmetropia - (normal vision)...The focal point is aligned properly to facilitate normal vision.

Trying to trick the eye to see something outside the corrective parameters with significant magnification or minification will probably not be tolerated very well.

[Spexvet]

I think the power of a lens defines its mag/minifaction. Asphericity will reduce it somewhat, but a plus lens will still magnify and a minus lens will still minify.


As to perception, you would think that the mag/minification of a given lens worn by someone would become their "normal" or baseline perception. That seems to make sense to me.

But in terms of behavior, my experience tells me that, while there are certainly plenty of exceptions, people with similar prescriptions have similar behavior patterns. I know this sounds like stereotyping. But I also know a lot of "hard headed hyperopes" - no offense intended to all of you hyperopes. Could these behavior patterns be caused by the way people "see the world" through their similar Rxs?

Does anyone else notice these character traits?

[CME4SPECS]

Pakev seems to be a little confused this mornin'!

[drk]

There was a study somewhere, sometime that put inverting prisms on a test subject, such that his world appeared upside-down. It was awkward, at first, and within a week or so he was riding a bike that way. His visual system adapted.

We deal with that all the time. When presenting prescriptions, there are desired effects and side-effects, and the person has to get used to the side-effects. Normally they do. The visual system is too plastic to be tricked for long.

So the answer to your quest would be that the temporary effect would be present, but it would disappear soon.

As to whether a lens can be made with pure magnification or minification effect without power effect: I'm virtually sure it's "no". It can be manipulated in a power lens, though.

magnification = shape factor + power factor

I'd have to look it up, but it's used in anisekonic lens design.

[Joe Stella]

***

[DocInChina]

I'm a phd student at Oxford, working on the philosophy of perception. I would like to ask for people's help on a question of optics. This question arose when I was thinking about the following hypothesis:

Could everything look smaller to you than to me, without there being any behavioural difference between you and me?

I am actually going to address the early part of your posting. Strictly speaking, from a behavioral standpoint, we visually measure our environment in space and time. A lens will effect light in space and time, therefore any individual will have a difference unto themselves with this regard. Additionally, each individual (even without a lens) has a slightly different interpretation of space and time. An example can be found at a crime scene or scene of an accident. Often there are different reports made by individuals questions. They all viewed the same thing but their individual interpretations were likely different. It can go deeper than this so if you care to PM me I would gladly give you a further explanation.

Doc

[1968]

...we visually measure our environment... An example can be found at a crime scene or scene of an accident. Often there are different reports made by individuals questions. They all viewed the same thing but their individual interpretations were likely different.

Doc, doesn't this have more to do with memory than with vision?

[CME4SPECS]

PAKEV, that's better!

[DocInChina]

Doc, doesn't this have more to do with memory than with vision?

It has to do with visual memory which still requires an interpretation of how each person sees the world around them. Visually we interpret what we see in terms of distance and time. The more skewed ones vision is, the less true is their interpretation of events around them.

Doc

[drk]

Total spectacle magnification (SM):

SM = (1/15) tF1 + (1/10) hFv

or,

Spectacle magnification = "shape factor" + "power factor"

t= center thickness (M)
h= vertex distance (M)
F1= front surface (base) curve (D)
Fv= back vertex power (D)

Thus, for a plano lens, while some minimal magnification effect is achievable from the shape of the lens, i.e. thickness and base curve,

(1/15) 0.005M (+10.00D) + (1/10) 0.013M (0.00 D) = 4%

its not very much, and you'd adapt to it quickly (some more so than others, all opticians will attest).

So you will not get the effect.

Interestingly, you can achieve a perceived size change in vision by using plano prisms by an entirely different mechanism, but you'd have a hell of a headache!

A note to Pakev: I think you must know this: the bright, pale, green-yellow color of some emergency vehicles is supposed to be 555 nanometers wavelenth, not coincidentally, the wavelenth of light the human eye is most sensitive to.

Another NB:
Plano wrap sunlenses do multiple screwy things to your eyes, and you can see one other factor above...a high base curve with some center thickness= some magnification. Remember, these things are worn part-time, so adaptation is less! But I'm not throwing out my Oakley display just yet!

[coda]

I believe the short answer to your question is: no. It is not possible to produce a lens which only magnifies the objects being viewed without magnifying the field on which they sit (which is really what you're asking for). The same thing goes for minimization.

Were I you I would move this experiment into the lab and use a computer display. In this case you can fix the field and paste into it objects over which you have relative size control and it would still be possible to maintain a semblance of reality. Of course this would be expensive, particularly if you wanted to get fancy with moving objects/animation.



A far cheaper approach would be to construct a diorama with a series of objects of differing sizes that are otherwise identical. If you wanted to use humans then you can construct two rooms of differing size (complete with ‘identical’ objects of differing size proportional to the room size), place a person in the room and have the subject view the room through a pinhole, this will give the illusion of the person being larger or smaller depending on which room they inhabit.



It would be interesting to hear what you do with this. Good luck.

[scat1134]

Thank you everyone for all your opinions so far. They've been very helpful. I'm benefiting a lot from them, so please keep them coming.

Today I've had another thought about how to define my question. Let's say that minimizing and magnifying effects are 'scaling effects', and increasing and decreasing the physical angle you see are 'angle effects'. I hope I'm being clear enough when I talk about increasing and decreasing the physical angle you see--I mean increasing and decreasing the quantity of the scene in front of you that you can see.

So my question can be put like this: can there, in vision, be scaling effects, either magnifying or minimizing, without angle effects?

Someone I'm in touch with tells me that there is a phenomenon called anisekonia, in which the image sizes in the two eyes differ. This phenomenon seems relevant to my question.

Let's say that Fred has anisekonia, and therefore the image size in Fred's left eye is greater than the image size in Fred's right eye. So, an apple looks larger to Fred when he has just his left eye open than when he has just his right eye open.

This entails that there is a scaling difference between the images in Fred's left and right eyes. So an interesting question here is: is there an angle difference between the two eyes? Does Fred see a smaller angle out of his left eye (with his right eye shut) than he does out of his right eye (with his left eye shut)?

If, in fact, Fred sees the same angle, i.e. the same amount of the scene in front of him, out of both his left eye (with his right eye shut) and his right eye (with his left eye shut), then it would appear that we have here a scaling difference without an angle difference.

If anisekonia really does involve scaling differences without angle differences, I'd be very interested to know. Many thanks!

[Chris Ryser]

.

Someone I'm in touch with tells me that there is a phenomenon called anisekonia, in which the image sizes in the two eyes differ. This phenomenon seems relevant to my question.

Let's say that Fred has anisekonia, and therefore the image size in Fred's left eye is greater than the image size in Fred's right eye. So, an apple looks larger to Fred when he has just his left eye open than when he has just his right eye open.

This used to be a common occurence in the old days when people had a cataract done on one eye only and we fitted them with a lets say +12.00 Diopter lens on one eye which gave them perfect vision.

If you left the old prescription as is in the non operated eye with which they did see normal, no cataract, they would have such a difference in size of picture.

Both eyes had a 20/20 vision but the size of the image was different. We then had to put an occluder on the non operated eye or make another +12.00 lens so they would not see properly at all (blurred).

[chip anderson]

Chris:

There was another solution back when we had skills enough to fit hard contact lenses. Fit patient with hard contact lenses, thereby eliminating ring scotoma, curved doorways, and a lot of good stuff. The image disparity was less and usally neglligable. When it was a problem you just cut the contact lens power until the images were tolerable (usually 20/30)) or so. This is still a problem today if power differences are over four (yea, some say 3 and some say 5) diopters and may be handled in the same way. Or one can find a Johns-Hopkins orthoptist and they will tell you how to calculate anisokonia lenses.

Chip

[drk]

I think you mean "field of view" and not "angle".

I believe that it is impossible to have an increase in magnification without a decrease in field of view and vice-versa.

Anisekonics may or may not be able to see such small differences in image size looking from one eye to the next. The difference is small. It does give them spatial distortion, however, as the brain tries to interpret the disparate images. Straight lines will appear slanted, depth perception is disturbed, flat surfaces will seem convex or concave, but only if the patient is not familiar with the scene he is surveying. If it's something familiar, his brain will override the distortion and it will seem more normal.

Chip,
One of the OD professors at OSU when I was there was kind of the world's leading authority on anisekonic lens design, and OSU was/ is the mecca for anisekonia. We all had to learn it, but we never had a real patient, as it is so rare a clinical entity.

Any anisekonia problems, see me, and I can calculate the lens design, if someone else can fabricate it.

[walleye]

These questions bring back old memories of physiological optics and visual training clinic at Pennsylvania College of Optometry in the late 1960's. We learned to use the Space Eikonometer possibly made by American Optical Co. Scat 1134-you should go to google and put in "Space Eikonometer" and find all sorts of technical info in reply to your questions. You could also try to get a hold of some hand held prisms of 1, 2 or 3 prism diopters and hold them binocularly looking at a page in front of you. Hold the prisms in the position of both base in, then both base out, then both base up, then both base down and see what you percieve.
I wish I could pursue this more now but I have to rush to my office to look at eyeballs and code insurance forms and argue with patients as to why they have to pay $15.00 for an eye exam and a pair of glasses and does'nt their HMO pay it all for them. Ah to be a student again!! Good luck.

[Andrew Weiss]

What might be interesting is to interview people who have a significant prescription (say, over a + or - 3.00) and who also wear contact lenses, and see whether they behave differently with their glasses on versus their contact lenses.

I am, in Spexvet's words, a "hard-headed hyperope" :hammer: I also wear progressives, and used to wear contact lenses. Like many contact lens wearers, I didn't want to take my lenses out and put my glasses back on, because the world felt more constricted to me with the glasses on than off. Yes, some of that has to do with the physical boundaries of the eyeglasses themselves, but some of it also has to do with the fact that the world appeared "wider", for want of a better description.

Since I've stopped wearing the CLs and wear my glasses exclusively, I can't say that I notice a difference in how I perceive the world. As drk and others have said here, the brain adapts. But it would be interesting to find out if anyone has noticed a difference in my behavior or personality

[Spexvet]

Anisekonics may or may not be able to see such small differences in image size looking from one eye to the next. The difference is small. It does give them spatial distortion, however, as the brain tries to interpret the disparate images. Straight lines will appear slanted, depth perception is disturbed, flat surfaces will seem convex or concave, but only if the patient is not familiar with the scene he is surveying. If it's something familiar, his brain will override the distortion and it will seem more normal.

Chip,
One of the OD professors at OSU when I was there was kind of the world's leading authority on anisekonic lens design, and OSU was/ is the mecca for anisekonia. We all had to learn it, but we never had a real patient, as it is so rare a clinical entity.

Any anisekonia problems, see me, and I can calculate the lens design, if someone else can fabricate it.

Drk, I see anisekonia quite often. The doc is great at calculating IOLs. They get one eye done and come to me with an Rx of OD -0.50 OS -4.50. The problem is, he doesn't warn them. So it's up to me to set their expectations, and tell them, "that's natural, Mrs. Jones". You forgot the 3-D effect of looking at an object and seeing a smaller image surrounded by a larger image. And then there's the slab-off issue - "it's HOW much???"

Chip,
I've seen people driven bonkers with a difference of only 2 diopters. It depends on the individual.

[drk]

Drk, I see anisekonia quite often. The doc is great at calculating IOLs. They get one eye done and come to me with an Rx of OD -0.50 OS -4.50. The problem is, he doesn't warn them. So it's up to me to set their expectations, and tell them, "that's natural, Mrs. Jones". You forgot the 3-D effect of looking at an object and seeing a smaller image surrounded by a larger image. And then there's the slab-off issue - "it's HOW much???"

Chip,
I've seen people driven bonkers with a difference of only 2 diopters. It depends on the individual.

Yikes! I hate it when cataract surgeons do that. I fit them in a contact, pronto. Good point!

I agree that 2D can be a problem.

[scat1134]

Here is a different way of thinking about the the hypothesis above--the hypothesis being whether it is possible to uniformly shrink the visual image, preserving all the spatial relations between the objects within the image.

What if you could shrink someone's retina, and also shrink the projection of coloured light onto that retina by the same degree? What would happen is that the pattern of stimulation by coloured light would be, in absolute terms, smaller than before, but it would have all the same proportions as the pattern of light that stimulated the initial, larger retina.

Would the visual image generated by the later, smaller retina be uniformly smaller than the visual image generated by initial, larger retina, with all the spatial relations between things in the image being exactly the same?

If there are subjects with different sized retinas in the two eyes, then one
could stimulate each retina with the same relative proportions of coloured
light (each time ensuring that the patient keeps the other eye shut), and
ask them whether the visual image from one eye is larger than the visual
image from the other.

Does anyone have any thoughts on the question above about the effects on the visual image of changes in retinal size, when those changes are accompanied by changes in the image-size projected onto the retina?

Many thanks.

[Chris Ryser]

Does anyone have any thoughts on the question above about the effects on the visual image of changes in retinal size, when those changes are accompanied by changes in the image-size projected onto the retina?

No body part on an animal or human body are exactly the same size, and that goes from legs to earlobes and eyeballs.

If the 2 eyes do not have the exact same physical measurements their optical system will have to have slight differences, however people do see the same.

Therefore the brain has to make the adjustment needed.