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Old Monday 13th January 2020, 15:55   #101
Pileatus
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The OP simply does not understand the difference between laboratory values and the realities of field use. The idea of using a handheld, non IS, 25X binocular for normal birding activities is ludicrous. Go to the hawkwatch in Cape May for three weeks straight in September/October and tell me how many you see. The answer is zero. You'll see very few 12/15X bins and countless 7/8/10 models of all variations around the necks of birders from around the world.

In the modern world it could and probably will be argued that the Cape May birding folks have no idea what they're missing and are nothing more than buffoons. One must rethink that notion, however, when one realizes they are in the presence of many of the authors of the most widely read and acclaimed birding books and guides. They are the world's foremost birding experts and they use 7/8/8.5/10X bins. I don't wonder why.

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Old Monday 13th January 2020, 19:58   #102
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Lee, re. #97

In #90 he claims "Of course, the 25x70 format is substantially too bright for daytime...." This has a Light power of 196 and the other combinations are similar, and even with EPs ranging from 2.8mm to 4.4mm they are all be "substantially too bright" for daytime birding. What do you think?

David
I have never tried a 25x70 but I doubt I would be dazzled. What do you think?

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Old Monday 13th January 2020, 20:04   #103
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I have never tried a 25x70 but I doubt I would be dazzled. What do you think?

Lee
My wonder is whether there is such a thing as an off the shelf (hand held) High Grade 25 x 70 for comparison? I cannot find anything akin to the build of say a Kowa Highlander. Once I looked through an Opticron or Binolyt 20 x 80 I think. (hand held ) for about 30 seconds, felt giddy rather than dazzled....... no disrespect to the optics, just could not keep the image steady.

Pat

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Old Monday 13th January 2020, 20:39   #104
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I have never tried a 25x70 but I doubt I would be dazzled. What do you think?

Lee
Never tried a 25x70 either, but I have good Pentax 20x60. Being dazzled because it is too bright is not an issue. Being useful on a tripod is also not an issue. Using it handheld as a binocular is ...well ludicrous.

I agree with Pileatus three posts above
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Old Monday 13th January 2020, 21:25   #105
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https://www.cloudynights.com/topic/5...t-impressions/ Do one, choose your own eyepieces to tune the power. Basically two spotting scopes strapped together. 4.5kg 45degree is certainly not hand holdable ;-)

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Old Monday 13th January 2020, 21:43   #106
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Celestron have a regular stand at the UK Birdfair and they put a bit more of their astro stuff on show a couple of years ago. I tried the 25x70 and 20x80 on tripods and the 15x70 hand held. I wouldn't have described any of them as bright, but the 20x80 was the best of the bunch.

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Old Monday 13th January 2020, 21:50   #107
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... as bright as spotting scopes normally are.
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Old Monday 13th January 2020, 21:54   #108
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There is a binocular Hartmann 25x80 in our collection. It is completely useless for handheld obervations despite its magnificent optical properties and very well constructed housing.
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Old Monday 13th January 2020, 23:58   #109
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The OP has presented yet another startling fact - that most, including those with vast field experience are simply unaware of - that many optics are too ‘bright’ for daytime use!
And that consequently, extraordinarily small exit pupils are to be preferred on hand held binoculars for general daytime use, including at extremely high magnifications

However, rather than getting drawn into arcana, let’s exercise some incredulity and apply some common sense


No conventional optic gives you a brighter image compared to the unaided eye, instead its use results in a loss of brightness
e.g. even those transmission champions Swarovski’s Habicht Porro prism binoculars have only 96% transmission

Of course using an optic may give you the impression of a brighter image, since it effectively brings the subject closer than when viewed unaided
e.g. when you view a subject at 20 meters with an 10x binocular, it’s as if you're standing at 2 meters when using unaided vision
- and the greater perceived detail is associated with a brighter image

I live in a part of the world where the summer light intensity is greater than many reading would regularly experience (it’s one of the world’s skin cancer capitals)
However, even on the brightest summer days none of my Swarovski Habichts are too bright, and nor is my EL SV 12x50

And the 6 mm exit pupil of the 7x42 is never too large. As is the case in any terrestrial viewing,
a larger exit pupil adds to both the ease and pleasure of the viewing experience

When you read a review of a telescope with a zoom eyepiece, you never see a phrase such as
‘. . . and while I wanted to test it at lower magnifications, the image was just too bright to comfortably see the detail’

And as Lee points out in post #97, the lighting intensity does often change markedly during the course of a day in the field
(and depending on the weather, sometimes repeatedly during the course of a day)


So really . . . ?


John


p.s. an opto-electronic night vision device does of course amplify the available light, and hence the image brightness, but that’s not the context here

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Old Tuesday 14th January 2020, 07:19   #110
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John

You have hit the nail on the head. I have occasionally been told that a certain bino model is too bright but when I pointed out that looking through binos is like looking through weak sunglasses due to the light transmission losses, I usually didn't hear any more about the excessive brightness.

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Old Tuesday 14th January 2020, 14:37   #111
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Rico it seems that you are really saying is that no one needs an exit pupil bigger than the size of their own pupil on a bright day.
That's right, Lee. What amazes you? Who has a 4-6mm pupil on a bright day?

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But I have been out on the islands of the west of Scotland where the sun was super bright in the morning and the sky covered with heavy black clouds in the afternoon while heavy rain was falling. In late autumn and in the winter when days are short and the day darkens rather early in the afternoon, you sometimes need all the light-gathering power you can get.
In these twilight situations, we will need twilight binoculars. It also seems a little "foolish" to make this comparison-example. Are you joking?
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Old Tuesday 14th January 2020, 14:41   #112
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I am a birder and vastly enjoy my (tripod mounted) 30x70 binoculars, two eyes is certainly better than one as we all know. If it gets a bit dim I swap down to 16x70 and keep going until you need more than optics to see stuff.
I'm glad there are also some birder with the right experience to testify.
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Old Tuesday 14th January 2020, 14:50   #113
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My wonder is whether there is such a thing as an off the shelf (hand held) High Grade 25 x 70 for comparison?
Unfortunately there is nothing lightweight HG 25x. Only some 15x and 18x (Swaro, Zeiss, Canon).
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Old Tuesday 14th January 2020, 15:01   #114
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The OP has presented yet another startling fact - that most, including those with vast field experience are simply unaware of - that many optics are too ‘bright’ for daytime use!
And that consequently, extraordinarily small exit pupils are to be preferred on hand held binoculars for general daytime use, including at extremely high magnifications

However, rather than getting drawn into arcana, let’s exercise some incredulity and apply some common sense
John, my friend. It would have been enough to read more carefully, to avoid the headache

try again:
the exit pupil is not the only factor to calculate the "light power" of binoculars, but it is essential to also use the magnification value. And in daytime hours (from sunrise to sunset), in the open field, the minimum power more than sufficient is on average equivalent to 7x17 = 8x18 = 10x20 = 25x32. Where to satisfy people with the lowest retinal sensitivity, simply increase the values to 7x21 = 8x22 = 10x25 = 25x40.

So, 25x70 = 7x37 (ep 5.3mm) = 8x40 (ep 5mm) = 10x44 (ep 4.4mm) are values that are far too "bright" for anyone. Mostly unnecessary and too heavy compared to the real need. ... in daytime hours

Sorry, but I have the impression of talking to those who don't want to listen.

There is no worse deaf than those who do not want to hear!

Last edited by Rico70 : Tuesday 14th January 2020 at 15:04.
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Old Tuesday 14th January 2020, 15:06   #115
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Never tried a 25x70 either, but I have good Pentax 20x60. Being dazzled because it is too bright is not an issue.
It's obvious to me too, but maybe not for everyone ...
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Old Tuesday 14th January 2020, 15:37   #116
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The image of the chimney pot at 124m in bright morning sunshine using a hand held 25x70 Skymaster was bright and large, but not too bright.
However, it quickly became silly because of the movement.
The sensible thing would be to tripod mount the 25x70 for viewing at 100m or more.

Or just use my Canon 18x50 IS hand held, which is perfect for the job.

I have had many instances of binocular images being too bright for me.
It depends on the lighting levels previous to using the binoculars.
If one has been indoors, especially in low light then going outside into bright sunshine is disturbing to me.
in fact I have to use sun glasses and a peaked cap.
This is mainly in the last ten years when I find bright sunshine disturbing.
I don't have cataracts and see quite well except being far sighted.

Formulae are being banded about as fact when they are not.
They are hypotheses.
Many statements have been made of opinions that are presented as facts.

Facts are when papers have been presented in peer reviewed learned journals with submitted dates and accepted dates.
I see none of that here.
Bold type insistence does not make opinion fact.
Forceful repetition of opinions does not make facts.

As to hand holding 20x80s and 20x60s I did this for years.
But on the sky where acuity is less important than light grasp and image scale.
Nebulae and galaxies that are invisible in 10x50s are readily seen in the 20x60 or 20x80.
Additionally pointing up in the sky gives more stability and for seeing faint extended objects a bit of movement is helpful.
But for examining Jupiter's moons stability is needed.

Nikon provide tripod adapters for the 16x50 Action but not for the 12x50 I think.
Skymaster provide a tripod adapter for the 25x70. It is there to be used.

Hand holding a 25x70 will reveal glimpsed coarse detail that is invisible with even a good 10x42.
But the fine detail is not seen.

There are many small zoom 25x binoculars. Most are unacceptable.
But the Pentax 8x-20x24 was admirable at 20x. Best of three that I had.

There are many quite good older Japanese 20x80s that reveal a lot more detail boosted to 60x or 80x.
But the binocular must be firmly mounted.

For birdwatching it is clear that 25x70s are a non starter, especially hand held and unbraced.
Because someone wants to do this, fine, but don't try to force it on others who don't want it.

There have been many statements made about all sorts of things that are incomplete or just wrong, but there is no point going point to point discussing this, because it is simply not productive or sensible to do so.

B.

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Old Tuesday 14th January 2020, 16:11   #117
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Rico70, post 114,
You keep insisting that magnification is a factor in image brightness. It is not, only the combination of light transmission and size of exit puil determine image brightness. Show me one physiscs textbook to prove your point (I have a few, since I did my PhD work about the effect of light on living matter).
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Old Tuesday 14th January 2020, 17:01   #118
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Rico it seems that you are really saying is that no one needs an exit pupil bigger than the size of their own pupil on a bright day...
Quote:
Originally Posted by Rico70 View Post
That's right, Lee. What amazes you?...
Hi Rico70,

Birders generally agree that larger-than-"necessary" exit pupils are a significant advantage for birding binoculars, and you will find plenty of discussion of this on BirdForum. The principle advantage is ease of eye placement, which helps for getting the best view possible of a bird as quickly as possible. This advantage applies in situations where standing and viewing is physically awkward. It also applies for those of us who dart our eyes off-axis in looking around the FOV when searching for birds within the FOV. When exit pupils are small, eyes must be kept fixed on the center axis, which is awkward, inefficient, and uncomfortable for many types of birding. Another advantage of big objectives is that when stopped down, as effectively happens when the pupils are contracted in daylight, the optical performance of a bin can, in practice, be improved in several ways over that of bin of the same magnification but with smaller objectives.

--AP
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Old Tuesday 14th January 2020, 20:26   #119
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I can confirm that using my big bins at high power with 1mm exit pupils is a right pain to get good eye alignment and no blackout! (Not to mention the much dimmer image... good in the moon though). For seeing detail stability is everything, tripod, internal stabilisation or a good bit of wall...

Peter
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Old Tuesday 14th January 2020, 22:54   #120
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Rico70, post 114,
You keep insisting that magnification is a factor in image brightness. It is not, only the combination of light transmission and size of exit puil determine image brightness. Show me one physiscs textbook to prove your point (I have a few, since I did my PhD work about the effect of light on living matter).
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Old Tuesday 14th January 2020, 23:26   #121
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John, my friend. It would have been enough to read more carefully, to avoid the headache

try again:
the exit pupil is not the only factor to calculate the "light power" of binoculars, but it is essential to also use the magnification value. And in daytime hours (from sunrise to sunset), in the open field, the minimum power more than sufficient is on average equivalent to 7x17 = 8x18 = 10x20 = 25x32. Where to satisfy people with the lowest retinal sensitivity, simply increase the values to 7x21 = 8x22 = 10x25 = 25x40.

So, 25x70 = 7x37 (ep 5.3mm) = 8x40 (ep 5mm) = 10x44 (ep 4.4mm) are values that are far too "bright" for anyone. Mostly unnecessary and too heavy compared to the real need. ... in daytime hours

Sorry, but I have the impression of talking to those who don't want to listen.

There is no worse deaf than those who do not want to hear!
Some homework for you...
https://imaging.nikon.com/lineup/spo...asic/index.htm
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Old Wednesday 15th January 2020, 01:24   #122
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200114

Rico70:

Rico, I think you are trying to offend the wrong people. Most folks have been exceptionally kind and patient with you. I speak with people from all over the world ... every week (Claudio Manetti from your country is a longtime friend) and I am beginning to believe that the problem lies not in your language barrier but with your understanding and experience barrier.

My interest in optics started at age 8 and I have spent my entire adult life in professional optical engineering and technologies, I published Amateur Telescope Making Journal (ISSN 1074:2697) for 10 years, made Chief Opticalman in the US Navy in record time, have published 4 books and several monographs on Optics, Telescopes, and Binoculars, coined the term “conditional alignment,” and taught optical engineering PhDs the difference between binocular collimation and conditional alignment.** In almost 50 years, I have never heard of “move vision, “light power,” or come in contact with a number of facts that seem to be known only to yourself.

I think my neighbors on BirdForum have been exceptionally kind. I would like to be. But you seem to shed facts and logic from knowledgeable people like water on a duck’s back. We all have to start somewhere. God gave us two ears and only one mouth; there was great wisdom in that. It seems, however, some of your assertions are from another dimension and I suggest before you start pontificating about optics that you spend a little time learning about optics. I would like very much to be your friend and have a long association with you on BF, but as long as you repeatedly ignore wise counsel or set that counsel at naught, it can’t be so. I realize that most newbies think binocular forums are totally about opinions. That is almost true but to overlook the helpful knowledge presented to you, thinking your pronouncements are facts that everyone—even those far more experienced than yourself—should embrace is a grave mistake.

** When I am forced to flash credentials, my more erudite friends take me to task. But you keep barreling forward, and I saw no other way to hopefully get your attention. It is my hope that you will join us—not as a superior, but—as a peer.

“Any fool can know; the point is to understand.” — Albert Einstein

Bill
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Old Wednesday 15th January 2020, 01:38   #123
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Show me one physiscs textbook to prove your point (I have a few, since I did my PhD work about the effect of light on living matter).
Maybe it was.....

Click image for larger version

Name:	51Vv0vqFDNL._SX394_BO1,204,203,200_.jpg
Views:	14
Size:	32.0 KB
ID:	715039

psst.... I just couldn't help that... it was right out there in front of me, so I went with it.... no offense meant, just a post to lighten the hearts of all you physicists, opticians, optical scientists, innocent bystanders, birders, do-gooders, friends, and cranky old men...
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Old Wednesday 15th January 2020, 03:32   #124
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Maybe it was.....

Attachment 715039

psst.... I just couldn't help that... it was right out there in front of me, so I went with it.... no offense meant, just a post to lighten the hearts of all you physicists, opticians, optical scientists, innocent bystanders, birders, do-gooders, friends, and cranky old men...
Steve Holzner, the author, was an MIT grad, earned a PhD. from Cornell and was on the faculty at both institutions.

https://www.legacy.com/obituaries/na...?pid=166827876

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Old Wednesday 15th January 2020, 07:29   #125
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That's right, Lee. What amazes you? Who has a 4-6mm pupil on a bright day?


In these twilight situations, we will need twilight binoculars. It also seems a little "foolish" to make this comparison-example. Are you joking?
Rico
Alexis has explained why exit pupils larger than the observer's own pupils is an aid to the comfortable use of binoculars.

As for twilight binoculars: these are very useful when you leave home in the twilight to watch twilight wildlife. It is not practical when leaving home on a bright and sunny morning to also carry pair of 56mm objective binoculars in case the day should darken or in case you stay out longer in the evening than planned.

But this means that what you seem to describe as the 'excessive exit pupil' of say an 8x42mm binocular becomes very useful if the day becomes darker.

Lee
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