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Nikon Monarch HGs in Cabelas Fall Catalog (1 Viewer)

Adhoc,

There are two specification stadards covered by ISO14133. These were revised last year and are the instrument resolution standard was actually relaxed for some models

The Synpix Knight D-ED x32 8.0" specification falls outside the higher 14122-2 standard but the x42 (5.5") and x50 (5.0") comply. Of course these are maximum values and individual sample may be better. They generally need to be quite a bit better to impress me. The best binoculars could be around 4.5", 3.5" and 2.5" or better for 8x32, x42 and x50 respectively, but I don't find that a reliable indicator of sharpness. As you know I find a stopped down resolution value very much more useful.

20/20 or 120 arcsecond acuity. Magnified 8 times, that gives a visulal limit on detail of 120/8= 15 arcseconds. Providing the stopped down resolution of the binocular is better than 15" it's the eyesight that will be limiting not the binocular. That $25 binocular had a stopped down value of 14.5". My best result for an 8x is 5.8" or 2.5x better.

Measured light levels, random distances, using USAF 1951, Snellen, Landolt C and tumbling E charts.

David
 
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Adhoc,

There are two specification stadards covered by ISO14133. These were revised last year and are the instrument resolution standard was actually relaxed for some models

The Synpix Knight D-ED x32 8.0" specification falls outside the higher 14122-2 standard but the x42 (5.5") and x50 (5.0") comply. Of course these are maximum values and individual sample may be better. They generally need to be quite a bit better to impress me. The best binoculars could be around 4.5", 3.5" and 2.5" or better for 8x32, x42 and x50 respectively, but I don't find that a reliable indicator of sharpness. As you know I find a stopped down resolution value very much more useful.

20/20 or 120 arcsecond acuity. Magnified 8 times, that gives a visulal limit on detail of 120/8= 15 arcseconds. Providing the stopped down resolution of the binocular is better than 15" it's the eyesight that will be limiting not the binocular. That $25 binocular had a stopped down value of 14.5". My best result for an 8x is 5.8" or 2.5x better.

Measured light levels, random distances, using USAF 1951, Snellen, Landolt C and tumbling E charts.

David

Trying to catch up here,
but isn't 20/20 (6/6) vision more like 60 arc seconds acuity?

:smoke:

" 6/6 is the visual acuity needed to discriminate two contours separated by 1 arc minute- 1.75 mm at 6 meters. "

https://en.wikipedia.org/wiki/Visual_acuity
 
Trying to catch up here,
but isn't 20/20 (6/6) vision more like 60 arc seconds acuity?

:smoke:

" 6/6 is the visual acuity needed to discriminate two contours separated by 1 arc minute- 1.75 mm at 6 meters. "

https://en.wikipedia.org/wiki/Visual_acuity

This is something that frequently crops up on forum. Due to a historical convention opthalmologists designed optotypes with feature differences of one arcminute for the 20/20 line. So the difference between an O and a C would be an one arcminute gap in the circle. The rest of the scientific world, including optical engineers, would call this a two arcminutes resolution. It's easier to understand if you consider a bar chart, where the bars and the gap between them is one arcminute. With a loss in resolution this pattern degenerates into a sine wave where the angle between the peaks is two arcminutes, 120 arcseconds of 30 cycles per degree. With the right software you don't need letters, bars or even star doublets. The resolution would normally be determined by analysis of the contrast spread of a straight edge (modulation transfer function).

Hope that helps.

David
 
This is something that frequently crops up on forum. Due to a historical convention opthalmologists designed optotypes with feature differences of one arcminute for the 20/20 line. So the difference between an O and a C would be an one arcminute gap in the circle. The rest of the scientific world, including optical engineers, would call this a two arcminutes resolution. It's easier to understand if you consider a bar chart, where the bars and the gap between them is one arcminute. With a loss in resolution this pattern degenerates into a sine wave where the angle between the peaks is two arcminutes, 120 arcseconds of 30 cycles per degree. With the right software you don't need letters, bars or even star doublets. The resolution would normally be determined by analysis of the contrast spread of a straight edge (modulation transfer function).

Hope that helps.

David

Ok, the ISO standard 5.5'' you mentioned for x42 is in Line Pairs I guess then?

If you have 20/10 eyes, (can see the last line on Snellen chart) and resolve aprox. 60 arc seconds LP, you would still be better than the ISO standard 5.5'' with a margin (60/8 = 7.5'') and eyes would be limiting?
And you would need fighter pilot eyes to come close to 5.5''?
Or are some bins not honoring the ISO standard? Sample variation etc.?

Still trying to catch up...perhaps did I miss the talk on hyperacuity? :smoke:

https://vrwiki.wikispaces.com/Visual+acuity

https://en.wikipedia.org/wiki/Visual_acuity#/media/File:Snellen_chart.svg
 
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Ok, the ISO standard 5.5'' you mentioned for x42 is in Line Pairs I guess then?

If you have 20/10 eyes, (can see the last line on Snellen chart) and resolve aprox. 60 arc seconds LP, you would still be better than the ISO standard 5.5'' with a margin (60/8 = 7.5'') and eyes would be limiting?
And you would need fighter pilot eyes to come close to 5.5''?
Or are some bins not honoring the ISO standard? Sample variation etc.?

Still trying to catch up...perhaps did I miss the talk on hyperacuity? :smoke:

https://vrwiki.wikispaces.com/Visual+acuity

https://en.wikipedia.org/wiki/Visual_acuity#/media/File:Snellen_chart.svg

The instrument resolution is measured for the full objective diameter and the current ISO standard for an 8x42 is 7.5". This measurement, has little useful value. Under optimum light condition the pupil of the eye will be about 2.5mm diameter. At 8x magnification that would correspond to just 20mm of the objective forming the image on the retina. The resolution for the objective stopped down to 20mm will usually be somewhat worse than the instrument resolution.

You are correct that someone with 20/10, 6/3 acuity with 8x magnification will effectively have a 7.5" acuity. An x42 binocular that just meets the 7.5" ISO standard will usually almost have a stopped down resolution worse than that and will therefore be limiting. There is a good chance that one with 5.5" will be too, but it's not inevitable. Most with 3.5" or better will usually be pretty good.

In an earlier post I drew a distinction between effective resolution and sharpness. While I can often distinguish detail differences down to 7.5" stopped down resolution . I've found I can also see sharpness or micro contrast benefits for binoculars with effective resolutions below that. Sores 6 to 10 correspond to stopped down resolutions from 7.5" to better than 6" but these were estimated by sharpness.

David
 
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Under optimum light condition the pupil of the eye will be about 2.5mm diameter. At 8x magnification that would correspond to just 20mm of the objective forming the image on the retina.
David

Over many years I have tried to verify this theory and, so far, the great majority of the circumstantial evidence is that this is fiction rather than fact.

I have not been able to find a source for this theory other than talk forums and would welcome any experiments that would prove this point of view to me.

As a simple test for those who wish to try for themselves.

Cut a 20 to within about 5 mm of the aperture circle out of opaque paper, wet it and stick it to the center of an objective lens. Then go outside on a bright day and describe what you see and how it relates to a 2.5 mm pupil using only the center 20 mm of the objective. As I see it, this pertains to the optical principle that for all objects in the field of view that both the entrance and exit pupil will be fully illuminated.
 

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Over many years I have tried to verify this theory and, so far, the great majority of the circumstantial evidence is that this is fiction rather than fact.

I have not been able to find a source for this theory other than talk forums and would welcome any experiments that would prove this point of view to me.

As a simple test for those who wish to try for themselves.

Cut a 20 to within about 5 mm of the aperture circle out of opaque paper, wet it and stick it to the center of an objective lens. Then go outside on a bright day and describe what you see and how it relates to a 2.5 mm pupil using only the center 20 mm of the objective. As I see it, this pertains to the optical principle that for all objects in the field of view that both the entrance and exit pupil will be fully illuminated.

Ron:

Thanks for setting the record straight, David does not know
all of which he claims.

Jerry
 
Over many years I have tried to verify this theory and, so far, the great majority of the circumstantial evidence is that this is fiction rather than fact.

I have not been able to find a source for this theory other than talk forums and would welcome any experiments that would prove this point of view to me.

As a simple test for those who wish to try for themselves.

Cut a 20 to within about 5 mm of the aperture circle out of opaque paper, wet it and stick it to the center of an objective lens. Then go outside on a bright day and describe what you see and how it relates to a 2.5 mm pupil using only the center 20 mm of the objective. As I see it, this pertains to the optical principle that for all objects in the field of view that both the entrance and exit pupil will be fully illuminated.

This is an excellent demonstration that our theories often are not fully founded on experimental fact.
Recognizing that and then finding a way to correct the misunderstandings is hard, even more so when it involves human perception.
I wonder how many more such misunderstandings lurk in cut and dried topics, apart from optics.
 
It was Ron that many years ago insisted that it was impossible for the eye to detect resolution differences in binoculars. It was quite evidently incorrect then, and I've met may along the way that would agree with me. Mostly thanks to Ron's misdirection it took me another year or so to figure out what was going on. It's a little amusing that it was the paper cut out test that I suggested Ron should try to prove my point. Like Ron I would urge you all to check it for yourselves.

I've done this in a rush so please excuse the crudeness of the cut outs the quality of the images. The first photo is just showing a paper disc just stuck to the objective with moisture. In order to see the resulting shading it is necessary to put a translucent screen at the exit pupil in order to show it and photograph it. I just used a strip of tissue paper. Ron's photos should be like these.

I hope my image is clear enough to demonstrate that the light from the periphery of the objective arrives at the periphery of the exit pupil, and would be blocked by the iris of the eye, exactly as I stated. The binocular effectively has a smaller objective. I can assure everyone that there is on trickery involved, masking an objective in this way most certainly causes blackouts when the light conditions are bright and proves my point. Try is for yourselves.

Ron, the only place I believe this has been published is in the German edition of Holger's book. Hopefully the English version will be along for too long. I have also discussed it at some length with some in the industry, most notably Gerold Dobler of Zeiss (ex Leica, ex Swarovski) who brought along some test results to BirdFair 3 years ago. Unfortunately he wouldn't let me scrutinise his MTF plots too closely, but confirmed what I was saying was essentially correct, and explained the compaints about the HT 8x54 at the time. He also acknowledged that Zeiss needed to revise their QC protocols. Something a forum member tells me the German representatives are telling cusomers they have done "to meet the expectations of the most exacting users".

David
 

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I usually know better than to disagree with Ron, since almost every time he’s going to be right, but on this one topic we have long agreed to disagree.

I’ve tried his experiment with opaque central obstructions of various sizes and today cooked up a variation using a translucent central obstruction. Below is part of my June 14 email to Ron.

“I modified the first experiment by using transparent tape to stick central obstructions of various sizes to the trim ring of my 8x56 FL. Looking north toward a cloudless sky in bright daylight a 30mm obstruction completely blacked out the FOV for a carefully centered eye. Reducing the obstruction to 27mm almost did the same, but only vey slight pupil movement caused a flickering of light to appear from the field edge. For 25mm or any smaller obstruction down to 15mm there was always some light at the edge of the field with the apparent size of the black spot of the obstruction decreasing in size with each smaller obstruction.

One possible explanation for why such a large obstruction was required for a complete blackout might be that my pupil was dilated beyond its normal size for the high light level by the dark obstruction covering most of the FOV for even the 15mm obstruction.”

I thought I might be able to minimize the tendency of my pupil to dilate when an opaque central obstruction blocks all or most of the light from the binocular exit pupil by using a translucent obstruction. I rummaged through a drawer and found an old 25mm eyepiece cap made of white translucent plastic. In the photos below you can see how I mounted it on the front of an old Zeiss 10x50 Porro, so that it blocks the central 2.5mm of the exit pupil.

I pointed the binocular toward a very bright area of sky not far from the sun, with the FOV including a spindly tree branch and some clouds, so I would know when the branch and clouds disappeared that the central obstruction was completely blocking the image forming light.

I found that with very careful centering of my pupil the clouds and branch did indeed disappear replaced by a featureless gray fog filling the FOV, indicating that my eye was closed to probably a bit less than 2.5mm and was not accepting any light from the objective lens outside the obstruction’s 25mm diameter. I would like to stress that the pupil must be very carefully positioned to prevent it from catching some image forming light just off the edge of the obstruction.

Before you accept the evidence from either side please do as Ron suggested and conduct the experiment yourself.

One last thing: Ron, check out page 171 in Rutten & van Venrooij, “Telescope Optics”. It’s not just the amateurs.

Henry
 

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"One last thing: Ron, check out page 171 in Rutten & van Venrooij, “Telescope Optics”. It’s not just the amateurs."

Henry is that Ray-Trace Results for Eyepieces? My book is copyright 1988.
 
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Henry,

Appreciate your contribution.

When I first tried these tests several years ago I had much the same experience. It was relatively easy to see that when I slotted a 20mm aperture in front of an objective while looking through the binocular there was no dimming of the view, but as you found, in the reverse experiment, with just the centre of the objective blocked, pupil dilation means the blackout might be very short lived. The results were more persuasive when using a high luminance view. For instance a bed sheet on the washing line in the sun on one occasion. Then, even a momentary glimpse of the bright surface when your will make the pupil contract again. It gives a more manageable working window to check out your eye alignment and such.

Henry, I think you may have been the first to draw our attention to the problems of the HT 8x54 so it was your observations I passed on to Dr Dobler and suggested that he should test it's stopped down resolution. Before our meeting at BirdFair I checked out a sample on the Zeiss stand and guessed the 20mm value was between 8.5" and 9.5". It sound like Dr Dobler had spent a little time on the fourm, and was initially quite dismissive of the criticism until I told him my visual estimate and he immediately got serious and produced a dossier of test results. He would not let me study the MTFs closely but even upside down I could see thay the 5% values were rougly 3 and 0.8 units, but there was no indication of what those units were. When I got home I went through the various unit options and figured they were probably cycles per minute. At 8x magnification that would be 2.5" and 9.4". I can't say for sure my reading of the plots or interpretation were correct, but I thought you might be interested. As I mentioned before, he concluded by saying Zeiss would be revising their QC protocols.

David
 
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"One last thing: Ron, check out page 171 in Rutten & van Venrooij, “Telescope Optics”. It’s not just the amateurs."

Henry is that Ray-Trace Results for Eyepieces? My book is copyright 1988.


Steve,

Mine's the fifth printing-2002. Maybe the page numbers shifted a little. The relevant part is below. I hope I can get by with reproducing this short excerpt from copyrighted material for "educational" purposes.

I don't think Ron would be persuaded by those passages. He already knows that's the conventional wisdom. As you would expect his contrarian arguments are sophisticated. So far, I haven't been able to follow them.

David,

Hard to explain why stopping down the 8x54 to 20mm would drop its resolution from 135/D to 188/D.

Henry
 

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Hi Henry;

I have no problem with “mechanically stopped” aperture changing resolution. The part I have been having a problem with for a long time is that the eye can stop an aperture that it can not even see. The only thing the eye can see is the already formed exit pupil.

On page 171 I take issue to the phrase “pencil of light”, this would imply a 2.5 mm bundle that translates to 20 mm of objective and this is easily understood for a narrow FOV instrument that is focused at infinity and a moveable eyepiece. The exit pupil of a 8x bino would have somewhere around 64° AFOV or 32° either side of the optical axis. The effective focal length (f#) change would have to be proportionally applied to the objective focal length, the distance through the erecting prisms, the eyepiece focal length and the field stop diameter. I can mathematically get close to the values at infinity focus but when I start shortening the objective focus distance the eyepiece FL and Field stop diameter start creating issues that I have been unable to resolve without changing some parameters such as magnification or FOV. This may be some issue with the focusing lens arrangement as opposed to a telescope that focuses by moving the eyepiece or something that I am missing in the erecting prisms.

I have used 8x20’s extensively and I always feel a brighter, more contrast and better image when I increase objective size. I do not feel like everything looks the same as 8x20 in daylight viewing.

I can not get away from the feeling, when using larger objectives, which I have some forward or rearward latitude with the bino placement for a good view and I attribute this to the FOV of the eye. At 100° FOV, the bino would only have to move back 1 mm for a full 5mm exit pupil to be in the FOV of a 2.5 mm pupil. Also keep in mind that the exit pupil still has DOF proportional to the object view.

What I see from the proposed experiment is distinctly different than your experience. When I place two 25 mm discs on the objectives of my 7x36 and take them outside on a bright day and look around normally I see a bright normal image but with two out of focus spots moving erratically around in the FOV. I have tried to focus on them and center them, but to no avail.

I was really hoping for more feedback, but besides your post, I have only had I PM and that sender saw the same thing I see.
 
What I see from the proposed experiment is distinctly different than your experience. When I place two 25 mm discs on the objectives of my 7x36 and take them outside on a bright day and look around normally I see a bright normal image but with two out of focus spots moving erratically around in the FOV. I have tried to focus on them and center them, but to no avail.

Ron,

I see the same thing as you if I try to use both eyes. I use only one eye which is enough to demonstrate the principle. It still requires critical pupil placement, but it's much easier to align only one pupil behind one obstruction.

Just now I went back to opaque obstructions and looked at a very bright cumulus cloud with my 8x56. It was relatively easy with careful positioning to achieve a complete blackout with a 30mm obstruction. A 25mm obstruction was difficult but just barely possible for a second at a time before my pupil would wander a little out of alignment with the obstruction.

Henry
 
Thanks Henry;

One other thing, if you try the experiment, use the eyecups as you normally use them.

I could duplicate Henry’s results, but only by fully collapsing the eyecups to the point I would get blackouts in any case, inside the exit pupil and using one eye.

Henry, are you using your normal eye relief setting? I am not able to get a blockage with my normal 1 click extended eyecup.
 
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Henry,

I can't swear to the accuracy of those values but I hope we can agree that the HT 8x54 was a rather peculiar binocular. I checked the results for 9 binoculars in my current notebook. Two were worse on stopping down, most were modestly better and one was dramatically improved stopped down. I don't know how much sample variation plays a part but I imagine the distribution of aberrations is very much part of the optical design process.

Dr Dobler emphasised that they specified that their models were always at least10% better than the ISO standard. That technically would be 7.5" for a 8x54, but from his explaination I think he meant the smaller objective standard of 240/D or 4.4", so that would be about 4". His MTF profile appeared to be better than that for full aperture.

Many thanks for posting that page. This arguement has been rumbling on fairly acrimoniously for years, but I always supposed that the likes of Carl Zeiss and Ernst Abbe knew this stuff 150 years ago, it just got lost in the computer age. Nice you found someone who hadn't forgotten.

David
 
Ron, Henry

Ron, I apologize for not trying your experiment yet. Now, with this discussion being so lively, I'll try to find the time to do it. As you know, my experience with small binoculars such as an 8x20 is very similar to yours. I have never been quite at ease even with a 10x32.

It is interesting to compare your description of the opaque/translucent disc obstruction experiment with Henry's. It sounds that you are trying to emulate normal viewing and Henry is trying to the best of his ability match a test bench setting. There are some questions I need to answer for myself about the 2.5mm exit pupil Leica Ultravid still, and your results may help in this.

Kimmo
 
Hello Kimmo, thanks for dropping in.

I was going to take a 10x40 monocular with about a 35 mm obstruction and place it on a tripod and try from normal setting for me, which shows a 4.2°
FOV and start backing off from the bino to see if as the FOV shrinks, indicating being on the optical axis, if the field would darken. But the weather here is not cooperating.

Based on your comments about bench test I went back to the bench and applied a rough shaped obstruction on the objective after aligning the camera and monocular optical axis. The camera was set to a 2 mm aperture. I tried to get to full FOV but the camera would no cooperate, so the pictures are from a little outside ideal viewing distance. I also got a little movement during the 1 and 2 second exposure times required for the small aperture.

This should have resulted in a 20 mm obstruction being able to obscure the view, but as can be seen it did not even obscure a 35 mm obstruction. I think the spot is a little off center because the stop is not centered very well.

Henry and I are still at the point of agreeing to disagree, hopefully you will see something we are both missing.
 

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Henry, are you using your normal eye relief setting? I am not able to get a blockage with my normal 1 click extended eyecup.

Ron,

Yes, normal eye relief setting. If I move my pupil too close the central obstruction shrinks and kidney-beaning begins to intrude from the field edge. Too far back and the central obstruction also shrinks along with the AFOV.

Kimmo,

Yep, I'm trying to eliminate everything that might effect the result other than blockage of the pupil by the obstruction. I found it impossible to center both pupils simultaneously behind fixed obstructions, even if the obstructions match the pupil size. I think the obstructions would need to move along with all the constant small involuntary pupil movements, not to mention jitters from hand holding. Also, I find that I need about a 3.5mm opaque exit pupil obstruction to counteract pupil dilation (and probably some jitter) even when I'm looking at brilliant white clouds.

Henry
 
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