I would be surprised that you would notice a difference in a 10x54 versus a 10x70 in low light. Usually you have to be under 50 to get any advantage out of a 7mm exit pupil binocular.
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best low light bino 10x (1 Viewer)
- Thread starter batvenci
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It sure would be if you are young enough to use a 7mm exit pupil.
If you are young your pupils can dilate to 7mm.
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That 14 to 16mm advantage in aperture wouldn't help you unless your pupils dilate enough to use the extra light. Think younger eyes. I once had a Fujinon 7x50 and I thought it was bright and then I compared it to a Swarovski Habicht 8x30 which was 1/2 the size. You know what. I could hardly tell the difference between the two in brightness in most situations.
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Chosun Juan
Given to Fly
Dennis, what's the source of that graph?
Ed once presented some other data which showed quite a bit more dilation than that graph as folks age ..... :cat:
Of course a dilated pupil is not just a one way trip down beneficial lane - there's the odd aberration travelling head-on the wrong way down that road too ....
I guess each person has to find their own preferred magnification/exit pupil diameter/objective lens size (~= weight) compromise and sweet spot B
Chosun :gh:
Dennis, what's the source of that graph?
Ed once presented some other data which showed quite a bit more dilation than that graph as folks age ..... :cat:
Of course a dilated pupil is not just a one way trip down beneficial lane - there's the odd aberration travelling head-on the wrong way down that road too ....
I guess each person has to find their own preferred magnification/exit pupil diameter/objective lens size (~= weight) compromise and sweet spot B
Chosun :gh:
CJ
Not sure of the ultimate origin of the graph but it is displayed by Televue on their website and they make stuff for astronomical use. This graph has also been posted on Cloudy Nights.
Lee
A colleague, in optics, measured his pupils as 7mm at age 65.
Another colleague almost as large.
Perhaps optics specialists and astronomers all have large pupils.
I think I read that persons in the Nordic countries have larger pupils.
My last proper photographic measure in 20 minutes total darkness was 5.9mm and 6.0mm at age 65.
I really wonder whether that much reproduced average pupil size graph was properly researched.
If you look at youngsters on T.V., say in the daft reality shows, or more or less any movie shot in low light, it is clear that their pupils are sometimes 8mm even 9mm.
Perhaps they are all on substances, but I doubt it.
The Ross 10x80 binoculars are huge but have around 8mm exit pupils, some may be to allow movement of the head.
I think it was mentioned here that another 10x80 actually had 7.5mm exit pupils.
Fuji would not make a 10x70 high quality binocular for no reason.
More to the point is the variability in low light detection by different individuals.
Some can only see magnitude 5.9 stars when other can see 7.9 magnitude stars. Same place same time. That is 6 times fainter.
Another colleague almost as large.
Perhaps optics specialists and astronomers all have large pupils.
I think I read that persons in the Nordic countries have larger pupils.
My last proper photographic measure in 20 minutes total darkness was 5.9mm and 6.0mm at age 65.
I really wonder whether that much reproduced average pupil size graph was properly researched.
If you look at youngsters on T.V., say in the daft reality shows, or more or less any movie shot in low light, it is clear that their pupils are sometimes 8mm even 9mm.
Perhaps they are all on substances, but I doubt it.
The Ross 10x80 binoculars are huge but have around 8mm exit pupils, some may be to allow movement of the head.
I think it was mentioned here that another 10x80 actually had 7.5mm exit pupils.
Fuji would not make a 10x70 high quality binocular for no reason.
More to the point is the variability in low light detection by different individuals.
Some can only see magnitude 5.9 stars when other can see 7.9 magnitude stars. Same place same time. That is 6 times fainter.
WJC
Well-known member
Etudiant:
Of course, you are correct. And, if we get into the super-duper deep theoretical optics, then, perhaps, diffraction of the iris might play a part. I find it interesting, however, that when I was pointing out some of the physiological reasons why straight mathematical calculations could not be used to thoroughly explain a perception of brightness, I was met with those math calculations. But, when I offer 2 simple—math-based sentences--totaling 10 words—people are ready to jump on the physiological bandwagon.
‘Seems I can’t win for losing. I think I am going back to bed. :cat:
Bill
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Those big 10x70 and 10x80 binoculars are made for astronomy. In astronomy aperture rules because the bigger the aperture the fainter the stars and Messier objects you can see and the resolution is higher allowing you to separate closer double stars.That is why you see people with 20 inch aperture Dobsonian telescopes.
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The 10x80 binoculars were not made for astronomy. They were made for low light level military use, in fact very similar to observing birds in similar conditions.
But they are heavy and bulky and independent eyepiece focus, so that is why they are not used for birdwatching.
As to double stars, those where one would use 10 times magnification are usually better observed with 10x30 or 10x42 binoculars. 10x70 and 10x80 make the double stars too bright to be split.
For fainter double stars one would use 20x60, 20x70 and 20x80 binoculars, not 10 times.
But they are heavy and bulky and independent eyepiece focus, so that is why they are not used for birdwatching.
As to double stars, those where one would use 10 times magnification are usually better observed with 10x30 or 10x42 binoculars. 10x70 and 10x80 make the double stars too bright to be split.
For fainter double stars one would use 20x60, 20x70 and 20x80 binoculars, not 10 times.
elkcub
Silicon Valley, California
Oh, you're back to pupil size again. Take a look at Fig. 9, pg. 4 of the Watson & Yellott paper. Age has its highest predictive value at low luminance levels, r-squared = 56%, and lowest predictive power at high luminance, r-squared = 21%. The fitting equations are linear.
To summarize, age is much less a predictive variable for daylight birding than for nighttime astronomy. It's all very clear.
Ed
To summarize, age is much less a predictive variable for daylight birding than for nighttime astronomy. It's all very clear.
Ed
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elkcub
Silicon Valley, California
Alan,
Given that you read the article, it may be worth another try. I believe you're missing the important connection with binoculars because you have this incorrect understanding (para. 2, post 95):
The field-stop necessarily decreases light throughput! That's what an optical 'stop' does. The area of the field stop 'aperture' is what allows light to enter the eyepiece and leave at the exit pupil. [If that aperture were zero, for example, no light would leave the instrument.] The amount of light leaving defines the exit pupil flux density, which can be renamed the corneal flux density as it enters the eye. The projection area on the retina corresponds to the 'adapting field' referred to in the Watson & Yellott paper, and the AFOV of the instrument. It's all very consistent and beautiful, IMO. Brightness is a function of corneal flux density, since the eye is an integrator.
Ed
There a lot of double stars that are best viewed at 7x to 10x. It depends on their separation in arc seconds and brightness. The big 10x80's might have been developed for military use but most civilian use now is Astronomy.
http://www.astronomy.com/observing/...ky/2006/12/fun-with-double-and-variable-stars
WJC
Well-known member
Oh, you're back to pupil size again. Take a look at Fig. 9, pg. 4 of the Watson & Yellott paper. Age has its highest predictive value at low luminance levels, r-squared = 56%, and lowest predictive power at high luminance, r-squared = 21%. The fitting equations are linear.
To summarize, age is much less a predictive variable for daylight birding than for nighttime astronomy. It's all very clear.
Ed
Years ago, a fellow wrote an article for ATMJ that I let slip through my editing—having more on your plate than you can handle will do that. He was describing how removing the flared secondary baffle on a certain SCT improved the image because it greatly reduced the central obstruction. I pointed out that while his perception might have changed, the central obstruction was still the same because there was a painted ring on the primary mirror with the same diameter as the maximum diameter of the baffle he removed.
He replied that “[didn’t] count because it was painted on.”
I tried to reason with him that the ring—somewhat larger than the primary baffle—still constituted a central obstruction.
He replied that “All the old masters say different.” Being familiar with some of the “old masters,” I asked him to name one. He said he couldn’t because “They’re all dead, now.” But, he hurried on to say that proof of his assertion was in all the classical literature. I asked him to state the appropriate chapter in each volume of that “classical literature.” He said he no longer had any of the books.
When sharing our conversation with one of his well-known associates, he shared a quote from this fellow’s wife: “Each morning, he wakes up to see just how many people he can ‘piss off’ before going back to bed.”
With that revelation, I stopped trying to push Gibraltar … uphill. Pontification is simpler than research and certainly caters to those long on opinion but short of facts.
My last comment was to ask a simple question. “Are you saying that if I painted out a 7-inch disc on the 8-inch mirror it wouldn’t affect the image because it wouldn’t constitute a “real obstruction” because it was paint as opposed to something metallic?
With that bit of logic, he got into a huff and we had no further contact … Amen! :cat:
Bill
HL Mencken is one of my heroes.
Ed,
Neither of us seems to have had any impact on the other. Yet, for the sake of others who have read our exchange or may read this exchange in the future I'd like to make a closing statement.
You believe I misunderstand what a field stop does. I believe you misunderstand what an exit pupil is, how an image is formed by an objective, the role of the ocular, and how the field stop of an ocular figures in the design and function of the combined objective/ocular system.
These are not merely matters of preference or personal opinion. They are also not issues of perception or physiology. For this reason, I would be happy to see what an optics designer or physicist/engineer with expertise in optics, has to say about our exchange with regard to the images produced by different optical instruments.
Best Regards,
Alan
Neither of us seems to have had any impact on the other. Yet, for the sake of others who have read our exchange or may read this exchange in the future I'd like to make a closing statement.
You believe I misunderstand what a field stop does. I believe you misunderstand what an exit pupil is, how an image is formed by an objective, the role of the ocular, and how the field stop of an ocular figures in the design and function of the combined objective/ocular system.
These are not merely matters of preference or personal opinion. They are also not issues of perception or physiology. For this reason, I would be happy to see what an optics designer or physicist/engineer with expertise in optics, has to say about our exchange with regard to the images produced by different optical instruments.
Best Regards,
Alan
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