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- Magnification and move vision: (1 Viewer)

Pileatus

"Experientia Docet”
United States
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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Troubador

Moderator
Staff member
Supporter
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?

Lee
 

PYRTLE

Old Berkshire Boy
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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Steve C

Well-known member
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
 

typo

Well-known member
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.

David
 

Gijs van Ginkel

Well-known member
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.
Gijs van Ginkel
 

John A Roberts

Well-known member
Australia
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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Troubador

Moderator
Staff member
Supporter
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.

Lee
 

Rico70

Well-known member
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?

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?
 

Rico70

Well-known member
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. :t:
 

Rico70

Well-known member
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!
 
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Binastro

Well-known member
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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Gijs van Ginkel

Well-known member
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).
Gijs van Ginkel
 

Alexis Powell

Natural history enthusiast
United States
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?...

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
 

wllmspd

Well-known member
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
 

WJC

Well-known member
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).
Gijs van Ginkel

"The enemy of knowledge is not ignorance, it's the illusion of knowledge." — Dr. Stephen Hawking
 

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