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Old Saturday 5th August 2017, 01:40   #51
NDhunter
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Originally Posted by etudiant View Post
It must be wonderful to have natural 20/20 vision.
Sadly, 300/400 with astigmatism does not correct well enough to permit useful personal contributions to this somewhat peripheral discussion.

However, I do think it is obvious that the alpha glass makers are under increasing pressure from technically comparable Asian producers. To retain alpha status, they will need to differentiate themselves better than they do presently, at least imho. A meaningfully tightened set of technical standards to ensure better product uniformity might be one aspect of such an initiative.

Perhaps Nikon has decided that alpha status is unrewarding under these circumstances. Their marketing strategy now appears to emphasize the Monarch line, all resolutely beta offerings sold at modest premiums, with only the WX line to maintain Nikon's status as a premier technology binocular supplier. So they meet the spec at minimum cost, while the halo product ensures that Nikon remains a name to be reckoned with.
You may have an idea of what Nikon is up to, but you don't have a clue
to what they have in the works.

The Monarch HG is a good example of what Nikon can do. It is the new leader in the mid-range, with the specs. of wide fov. and overall quality. A nice thing
in the 100th Anniversary year.

Read the Allbinos review for more, and how it ranks near the top.

Jerry
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Old Saturday 5th August 2017, 04:23   #52
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Originally Posted by NDhunter View Post
You may have an idea of what Nikon is up to, but you don't have a clue
to what they have in the works.

The Monarch HG is a good example of what Nikon can do. It is the new leader in the mid-range, with the specs. of wide fov. and overall quality. A nice thing
in the 100th Anniversary year.

Read the Allbinos review for more, and how it ranks near the top.

Jerry
Jerry,
It is quite true that we have no clue as to what Nikon has in the works.
We can only speculate based on what they do publicly.

Nikon is currently hurting, reflecting weakness in camera and industrial optics sales, so resources are scarce. Even their modest 100th anniversary offerings are coming out late.
Nikon Sport Optics has a coherent strategy, they set a new benchmark with the WX and address the mainstream with the Monarch line. Adding a new alpha line now is unnecessary for them imho.

You may see it differently, that is what makes horse races.
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Old Saturday 5th August 2017, 10:53   #53
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Are you sure you have only 20/20 vision? Some optometrists tell clients that they have "perfect 20/20 vision" so long as that standard is met, when in fact many have better vision than that...
Jerry, I would repeat that cautionary question and comment. Some optometrists are reluctant to say anything beyond this even when asked, apparently for fear that they may be taken to have certified better acuity than they are familiar with measuring.
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Old Saturday 5th August 2017, 14:44   #54
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Originally Posted by etudiant View Post
Jerry,
It is quite true that we have no clue as to what Nikon has in the works.
We can only speculate based on what they do publicly.

Nikon is currently hurting, reflecting weakness in camera and industrial optics sales, so resources are scarce. Even their modest 100th anniversary offerings are coming out late.
Nikon Sport Optics has a coherent strategy, they set a new benchmark with the WX and address the mainstream with the Monarch line. Adding a new alpha line now is unnecessary for them imho.

You may see it differently, that is what makes horse races.
Etud,

The latest quarterly financial results are indeed! showing both revenue and profitability downturns in many key streams.

On the photographic front I would be disappointed to see them abandon the interchangeable lens 1" sensor range - there was enormous potential there for high crop factor (2.7x) lightweight, high speed, high performance sports/wildlife photographic systems. I'm glad that they seem to have dropped the DL compact line though - that looked like being on a hiding to nothing considering the ubiquity and camera advances in smartphones.

The high end DSLR body future looks good - based on rumours so far even I might be tempted into a higher expenditure FF setup if the new D850 has the D5's AF system, and 44Mp, and up to 10fps ....
Their lenses though need upgrading to achieve the performance and light weight of the Canon offerings.

Given that no-one has yet implemented mirrorless technology in mid - larger sensor sizes to take full advantage of the reduction in system form factor, an opportunity exists for Nikon to leapfrog to the head of the pack, especially if combined with their patented curved sensor technology. Perhaps that opportunity is an unexpected upside of them lagging the field in the mirror less area, and even with scarce economic resources, could be a decisive move given an astute enough strategic decision.

I am less thrilled with the strategic direction in the Sports Optics market though, (despite Jerry's assertions) .....

While Nikon deserve full marks for their value engineering choices regarding wide Fov and light weight in the new Monarch HG line, I feel they have dropped the ball in not offering class leading sharpness (going by reports of those with better than 20:20 vision) and brightness. The EWA WX line is also an interesting kettle of fish which is to be commended, but with IF and at circa 2.5kg they are mounted astronomy observation instruments etc, and not really viable birding binoculars.

I believe there is room for Nikon to incrementally upgrade both the EDG and SE ranges to offer higher performance (wider Fov's, more transmission brightness, HT and Ultra FL glass, and lighter weights, and seal the deal with clear class leading sharpness/resolution). They should also sort the Customer Service offering out to be more in line with a leading Alpha company. These upgrades wouldn't be prohibitive resource-wise as it's more implementing existing technologies /better management, rather than investing in new innovations.

It just needs some savvy strategic direction ..... call me, Nikon!


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Old Saturday 5th August 2017, 15:32   #55
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Quote:
Originally Posted by Vespobuteo View Post
The quote says "any good binocular". Bad samples is another question.
Vespo,

The post you linked is from 2004. I have learned quite a bit since, and like David says, would revise that statement now. You can find plenty of later posts that reflect my current views much better. My present take is very close to David's stand on this. We have some differences of opinion, but they are relatively minor.

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Old Monday 7th August 2017, 09:41   #56
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Jerry, ...... You have given your MHG a pretty good rap. I know you have had the 10x42 SF, and 8.5x42 SV for a long time - how do you find your 10x42MHG in comparison to them? Specifically in the areas of:-
1. Resolution/ Sharpness
2. Microcontrast
3. CA handling
4. Brightness
5. Colour cast
6. Vividness of colour at the extremes of the spectrum (ie. the purples/blues, and reds)?

Thanks!
Jerry ,

I see on another thread that after a quick trip to the optometrist that you now have 20/10 vision

Some others that have since viewed the MHG haven't been that impressed. It would be interesting to hear your take on the questions I asked earlier (quoted above) .....

You could also include comparison with some of your other binoculars for reference too if you want, and indeed resolution chart testing and/or some typo of numerical sharpness ranking as David has done if you are so inclined.

Do you see a difference in Sharpness between the MHG and other binoculars?



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Old Monday 7th August 2017, 16:36   #57
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I have Monarch 8x42 HG and I do not see any difference in sharpness between it and my Leica 8x42 Ultravid BL or my old Nikon 8x32 HGL or my Nikon 8x32 SE. The latter two have a flat field views which the Monarch HG does not. These are the only quality 8x binoculars I own and I have used all of them extensively.

What I do see is a smaller sweet spot than the Leica and the HG L and SE have which causes some lack of sharpness outside of it. It is caused by pincushion curvature which can be dialed into sharpness if needed which is not important to me because the minute movement I have to make to center the object will take care of that.

This binocular has a "field flattener" but it does not have a "flat field of view" like my SE, HGL and my 10x32 EDG has.

I remember someone else here also noting that the sweet spot of the Monarch HG was somewhat smaller than some Alpha binoculars had.

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Old Tuesday 8th August 2017, 00:16   #58
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Jerry,

How many days or weeks do you spend in the optometrist's chair deciding which lens is sharpest? ;-)

Just want to point out a little morsel of information that might put things in perspective. The ISO resolution standard that all the major players work by is 240/D. I'll skip the maths, but if that level or resolution was uniform acoss the objective it would translate effectivelyas 20/16 acuity cut off. Fortunately most come out a bit better than that, but not every sample, or every model.

I've resolution tested about 30 binoculars that I either own, or have had for at least a couple of weeks to review. The stopped down values (20mm for an 8x) range from an amazing 5.8" to the pretty miserable 14.5". That approximates to 20/7.7 and 20/19. That will give you a pretty good idea if a binocular will look soft for your eyesight. Even that $25 roof have sufficient resolution for those with 20/20 vision but differences in microcontrast or sharpness with better binoculars might still be evident. You will have to take my word for it that I can see such differences in resolution, but it was easier a couple of years ago when my acuity was 20/11or 20/9 with two eyes... on a good day!


To keep things simple, rather than use arcsecond or VA values I'll just use a 'Typo score' of 1 to 10 for the rest of this post and roughly cover the arcsecond equivalent of equivalent of 20/20 to 20/8, so even 1 will be quite acceptable for some. These are visual estimates in most cases are based on comparison with my own binoculars and others available when the light is close to optimal for visual acuity. I don't rate resolution in poor light. If go to Birdfair or a retailer I'll normally take my ZenRay Prime 10x42 or Vanguard EDII 8x42 for reference. I would score those as an 8 and 8.5 respectively though I need a tripod for the decimal points. These were very good for the money when I got them, but the market is improving all the time and I would certainly look for better with newer, more expensive models (if I had the money). What follows are some memorable comparisons.

UK launch day for the Zeiss Terra.
Terra
S1: 3
S2: 6
S3: 5
S4: 9
Conquest HD
S1: 8
S1: 7
S3: 7
S4: 8
HT 8X42:
S1: 9
S2: 9+
S3: 8+
HT 8x54: 5

About 4 or 5 years ago on the Swarovski stand. I think there have been at least 4 versions of the ELSV 8.5x42, and this was when the second, and to my mind the worst version was around.
CL
S1: 3
S2: 3
S3: 3
S4: 4
ELSV 8x32
S1: 9
S2: 9
ELSV 8.5x42
S1: 7
S2: 7
SLC
S1: 9
S2: 8

Vortex Razor HD
8x42: 8
10x42: 8
10x50: 9+

Meopta Meostar
8x42: 8
10x42HD: 9
12x42HD: 10

Kowa Genesis 8.544: 10
KITE Bonelli 2.0: 10
Nikon EDG: 9+
Nikon Monarch HG: 7
Opticron DBA VHD: 7

The following is acompilations from different occations
Leica
UV: 8
UV: plus 9
Noctivid: 10
Trinovid HD: 8
Trinovid: 6

I think this illustrates that not only is there variation between models there is variation between samples. That is particularly evident at lower price points as the Terra samples show. I've seen samples of amongst the cheaper models from Vortex, Kowa, Opticron, Kowa, Minox, Celestron, Hawke and Nikon that would score 8 or occasionally 9, but that wouldn't represent the model as a whole. The Fujinon KF 8x32W, a Sightron clone I reviewed, scored a 10 (confirmed by testing) but I would be very surprised if that was representative of the model. I now have measured results of '10' for the Meostar HD12x50 and Kite Bonelli 2.0 as well.

I've now tried 4 samples of the Monarch HD on three separate occasion and I'd score them all a 7 for apparent resolution. I've said twice already I like the ergonomics and other characteristics, so I find that a disappointment. It's no surprise to me, as I have explained that others might judge it differently

Now Jerry, over to you. What's your acuity, and what are your resolution scores for those models? Obviously we need them backed up by resolution testing, "you should have the skills". In arcseconds please, I can take it.

David
David, what would the Canon 10x42 L IS score with your method ?
Presumably higher with the IS off ?

The new Nikon WX 10x50 IF must of turned the dial up to 11...
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Old Tuesday 8th August 2017, 10:55   #59
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David, what would the Canon 10x42 L IS score with your method ?
Presumably higher with the IS off ?

The new Nikon WX 10x50 IF must of turned the dial up to 11...
Although I've tried the whole Canon IS range on a number of occasions, I haven't compared them to a bunch of other binoculars, so I'm a bit uncomfortable about scoring them. The 10x42L was obviously the best optically and the 8x25 didn't impress at all. I mentioned a '10' binocular is pretty obvious when you see it. The 10x42L wasn't a 10 but it there is a very good chance it was a 9.

I'm sure the WX is a wonderful binocular, but unless they have managed to rewrite the rules of physics it couldn't beat a 10. The demands of binocular astronomy are quite different from terrestrial viewing and actually much less exacting on effective resolution. However for that money, I'd certainly expect a 10. I hope they have one on the Nikon stand at BirdFair in a few weeks to see for myself.

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Old Wednesday 9th August 2017, 17:15   #60
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David, intrigued by the current thread on Snypex (here) I visited their website. In the Specifications for each model is an item named "Resolution". It gives the figure 8 for their 32 mm ED and D-ED models, 5.5 for the 42 mm models (ED/D-ED) and 5 for the 50 mms (ED/D-ED).

This (present) thread has startled me and not me alone. First that $25 statement. It is too stark and needs to be qualfied, as indeed Paddy7 has done: "A $25 high-resolving bin may be saddled with other problems that would stop you buying it." Then Jerry adjusts the focus control on his personal record and we see his acuity resolving from 20/20 to 20/10.

David, how did you measure your acuity, and
Jerry, how did the optometrist now measure yours?
Thank you both!
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Old Wednesday 9th August 2017, 20:29   #61
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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

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Old Thursday 10th August 2017, 15:34   #62
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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?



" 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
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Old Thursday 10th August 2017, 17:13   #63
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Trying to catch up here,
but isn't 20/20 (6/6) vision more like 60 arc seconds acuity?



" 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
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Old Thursday 10th August 2017, 19:49   #64
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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?

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

https://en.wikipedia.org/wiki/Visual...llen_chart.svg

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Old Thursday 10th August 2017, 21:28   #65
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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?

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

https://en.wikipedia.org/wiki/Visual...llen_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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Old Thursday 10th August 2017, 23:11   #66
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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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Old Friday 11th August 2017, 02:43   #67
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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
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Old Friday 11th August 2017, 03:16   #68
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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.
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.
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Old Friday 11th August 2017, 07:31   #69
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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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Old Friday 11th August 2017, 18:50   #70
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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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Old Saturday 12th August 2017, 02:18   #71
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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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Old Saturday 12th August 2017, 07:43   #72
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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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Old Saturday 12th August 2017, 15:46   #73
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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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Old Saturday 12th August 2017, 19:59   #74
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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.
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Old Saturday 12th August 2017, 21:05   #75
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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
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