Thoughts about Swarovision and Flat FOV (1 Viewer)

[Holger Merlitz]

Found this...http://www.journalofvision.org/content/12/10/12.full

A lot of info about eye pupil diameter.....

First time i heard about the monocular effect....scroll down in the hompage.


Anders

Terrible! It took me half a year of studying countless sources in order to compile a similar amount of data for my book - had this summary been around a year ago, it would have saved me lots of time ;-)

Great article indeed!

Cheers,
Holger

 

[Surveyor]

RonH,

I agree.

The way I look at the eye is as separate components. The lens is a matter of optics that refracts light in known and predictable ways.

The rod/cone and brain structure with chemical and aperture adjustments are perceptual in nature.

Resolution of the lens and acuity of perception are two different things and I believe that under certain conditions, such as vervier lines, highly defined boundaries or contrast (MTF) that the eye is capable of perceiving the higher resolution of larger aperture, better resolution optics when different optics are viewed with the same pupil diameter.

I almost always perceive a better image with larger, high resolution binos even in the brightest light. If there was no difference, nobody would carry 42 or 56 mm binos and just use 8x20’s to match their pupil diameter.

 

[Leif]

I almost always perceive a better image with larger, high resolution binos even in the brightest light. If there was no difference, nobody would carry 42 or 56 mm binos and just use 8x20’s to match their pupil diameter.

Almost all 8x20 bins have a narrow field of view, and in a country such as England there are few occasions when they provide as bright a view as an 8x42. Optically my Zeiss 8x20 Classic provide rather good on axis views, and competes with larger instruments. Having used it on long distance runs, it is more than sharp enough on axis for me. I suspect birders do not obsess about tiny differences in sharpness, which in practice make little or no difference.

 

[typo]

I suspect birders do not obsess about tiny differences in sharpness, which in practice make little or no difference.

Leif,

I wouldn't claim any birding talent but, amongst other things, it was the realisation that which binocular I used really did matter when trying to tell a Red Kite from a Buzzard at long distance that started me along this tortured path.

David

 

[Leif]

Leif,

I wouldn't claim any birding talent but, amongst other things, it was the realisation that which binocular I used really did matter when trying to tell a Red Kite from a Buzzard at long distance that started me along this tortured path.

David

David, the point I was making is that although my 8x20 provides excellent on axis sharpness in very good light, such conditions are all too rare where I live. Of course in good light they could theoretically be as sharp as the larger instrument. In normal light the image is somewhat dim, which reduces the detail I can see, so whether or not they are sharp in very good light is usually unimportant, in practice they are not sharp. So for me the choice of a larger binocular is dictated by light gathering and field of view. I happen to prefer an 8x42mm instrument, but that is really because they have longer focal length objectives than 8x32mm instruments, which translates into better IQ.

Incidentally I am referring to exceptional sharpness, and to make use of it I need to rest my elbows on a steady surface, or use a tripod which never happens in practice. I do not know which binoculars you were using, and how representative they are.

Something I asked earlier, not sure which thread, is about the sample variation for a given model of binocular. Some popular online review sites compare the sharpness of different models, and for that to be a valid methodology, we have to know something about sample variation for a given model, and how it compares to sample variation across difference models. I have never seen that done. (I am referring to sharpness in good light, rather than full aperture resolution.)

And as an aside, I wonder how many professional birders take a sample of binoculars, test them, and choose the best one? I know of people who have done this with camera lenses, but not binoculars. I am sure there must be someone here who does that, although with high end instruments the problem is that many UK dealers only stock 1 sample. And in some cases the dealer will not sell the demo model, and you have to wait for it to be delivered to your home, so you cannot even check that one sample.

 

[kabsetz]

RonH,
Resolution of the lens and acuity of perception are two different things and I believe that under certain conditions, such as vervier lines, highly defined boundaries or contrast (MTF) that the eye is capable of perceiving the higher resolution of larger aperture, better resolution optics when different optics are viewed with the same pupil diameter.

I almost always perceive a better image with larger, high resolution binos even in the brightest light. If there was no difference, nobody would carry 42 or 56 mm binos and just use 8x20’s to match their pupil diameter.

This has been my experience throughout my testing career, and it has bothered me that explanations for why and how it would be if, indeed, it even is so, have been hard to find. Arguments to the contrary have been much easier to come by. I still don't have good explanations, but I did some testing yesterday that gave very interesting results and which I may post in a day or two. However, a little bit more peer reviewing may be needed first, and it may be that I'll follow this with a "never mind" post.

Just to pique everyones interest.

Kimmo

 

[Surveyor]

I'd just add that a diffraction limited eye would be roughly 20/8 vision (48 arcseconds); very, vey rare indeed and something like 20/15 would be much more common (90 arcseconds).

David

Ronh, David;

I have the dubious luxury of knowing quiet a bit about my eye lens, thanks to cataract surgery. I have attached the data sheet for my SN60WF interocular implants.

Basically the transmission is 90% with blue blocker starting to kick in a little above 500 nm.

Backtracking from the MTF graph the 3 and 5 mm aperture measured results are about 29" for between 45 and 50% contrast, that is based on 20d @ 140 lp/mm, right at diffraction limited. If that holds up to the useful diameter of 6 mm dia. then may go as low as 19".

Useless info but thought it might interest you.

Ron

 

[ronh]

Interesting, this age we live in. If you just had retinal implants to keep up with them, you'd be set.
Ronh

 

[elkcub]

All,

What appears to be left out of this discussion is the f# of the objective lens. Large aperture binoculars tend to have longer focal length objectives, which means that for a fixed exit pupil (let's say 2.5mm) the effective aperture has a larger f#. (The 'effective aperture' is determined by the user's pupil diameter.)

Our ability to detect lens aberrations, however, is determined by their magnified size on the retina (resulting in blur), so the effect of even a relatively small f# will only be perceived if the aberrations exceed some minimum strength. If the magnified aberrations are close to the threshold of perception, we should also expect to see increased diversity of user acceptance because detection thresholds vary considerably in the population, and in particular with age. A strong implication, also, is that there is less wiggle room in the design and manufacture of small pocket binoculars, which may account for why there are so very few good ones to select from.

Ed

PS. For those interested, a very well documented and interesting overview of this general telescope-eye interface area is presented at this site: http://www.telescope-optics.net/combined_eye_aberrations.htm

 

[Leif]

All,

What appears to be left out of this discussion is the f# of the objective lens. Large aperture binoculars tend to have longer focal length objectives, which means that for a fixed exit pupil (let's say 2.5mm) the effective aperture has a larger f#. (The 'effective aperture' is determined by the user's pupil diameter.)

I did mention it a few posts earlier. |=)|

Aberrations including field curvature must be more tiring for the eyes, and not just fodder for high maintenance visual systems. And I do wonder if aberrations that are borderline observable contribute to eye strain.

 

[elkcub]

I did mention it a few posts earlier. |=)|

Aberrations including field curvature must be more tiring for the eyes, and not just fodder for high maintenance visual systems. And I do wonder if aberrations that are borderline observable contribute to eye strain.

Sorry, Leif, I missed that statement in your post #65. Quite right. :t:

Ed

 

[hinnark]

Our ability to detect lens aberrations, however, is determined by their magnified size on the retina (resulting in blur), so the effect of even a relatively small f# will only be perceived if the aberrations exceed some minimum strength. If the magnified aberrations are close to the threshold of perception, we should also expect to see increased diversity of user acceptance because detection thresholds vary considerably in the population, and in particular with age.

Thanks Ed for pointing that out. Everybody in this thread seems to refer to the optics of the eyes. But this is only one part of the problem to determinate the resolution power of the human eye. According to many references the number of cones in the retina, that is to say its central part, the fovea, is the limiting factor of resolution and the one that is responsible for that often-quoted 1 arcminute number.

Steve

 

[elkcub]

Hi Steve,

True, and along that line it's also worth noting that only about 50% of the neural transmissions passing through the optic nerve originate at the fovea; the remainder come from the very much larger extrafoveal regions that constitute the remainder of the retina. The visual performance of the extrafoveal area is almost never discussed, except for an occasional nod to peripheral motion detection. It is an active area of research, however, that I'm sure has implications for visual instruments.

I've attached just a sample article that was downloaded from the Journal of Vision website, which it should be noted is a unique resource that distributes high-quality peer reviewed articles for free over the Internet. Woweeeee! (in English too. )

I must have a little Johnny Appleseed in my genetics. |8)|

http://www.journalofvision.org/content/7/14/13.abstract

Regards,
Ed

 

[hinnark]

Resolution - spatial and temporal

Hi Steve,

True, and along that line it's also worth noting that only about 50% of the neural transmissions passing through the optic nerve originate at the fovea; the remainder come from the very much larger extrafoveal regions that constitute the remainder of the retina. The visual performance of the extrafoveal area is almost never discussed, except for an occasional nod to peripheral motion detection. It is an active area of research, however, that I'm sure has implications for visual instruments.

I've attached just a sample article that was downloaded from the Journal of Vision website, which it should be note is a unique resource that distributes high-quality peer reviewed articles for free over the Internet. Woweeeee! (in English too. )

I must have a little Johnny Appleseed in my genetics. |8)|

http://www.journalofvision.org/content/7/14/13.abstract

Regards,
Ed

That's all very very interesting indeed. It will take some time for me to read through. However, one thought comes to my mind that there isn't only a spatial resolution but also a temporal one. The temporal resolution is much better in the peripherial extrafoveal area than in the central fovea part of the retina. I remember those old CRT displays. When I looked directly on the screen there was no flickering. Whenever I've had look aside in a off target way, I was able to detect the flickering up to about 100 Hz. The computer experts use to tell me that isn't possible and I should only able to see the flickering up to 75 Hz. But this is an example of temporal resolution. I think during evolution it was important to detect any fast moving objects coming closer as soon as possible.

Steve

 

[elkcub]

That's all very very interesting indeed. It will take some time for me to read through. However, one thought comes to my mind that there isn't only a spatial resolution but also a temporal one. The temporal resolution is much better in the peripherial extrafoveal area than in the central fovea part of the retina. I remember those old CRT displays. When I looked directly on the screen there was no flickering. Whenever I've had look aside in a off target way, I was able to detect the flickering up to about 100 Hz. The computer experts use to tell me that isn't possible and I should only able to see the flickering up to 75 Hz. But this is an example of temporal resolution. I think during evolution it was important to detect any fast moving objects coming closer as soon as possible.

Steve

Steve,

Your experience is consistent with what I recall about critical flicker fusion. It decreases with age and retinal eccentricity, but increases with light intensity. 100 Hz does seem to be rather high for flicker fusion, but you were young, and the screen was bright.

Ed