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7mm exit pupil

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#1 warpsl

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Posted 18 February 2020 - 03:08 AM

I just recently acquired some old nippon 7x50,s.they are optically excellent. But I was worried about my 50 y o eyes not being compatible with a 7mm e p.i just did a daylight test.i measured my entrance pupil at 3.5mm.i then looked through my 8x30,s which gave me a similar exit pupil.then I looked through the 7x50,s.and the latter were noticeably brighter,even though my entrance pupil was only 3.5mm,and receiving only half the light of the 7x50.perhaps the larger pupil rays are absorbed by peripheral vision?the 7x50 was definitely brighter,

#2 sg6

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Posted 18 February 2020 - 03:51 AM

I would suspect that the 7mm is for fully dilated and so at night in the dark and with whatever chemical it is that causes better night vision present, not during the day.

As binoculars are "fixed" then a 7mm exit pupil seems around normal and people use that millions of times every day without thought or concern. You will after all be driving your car at some deadly speed with a 3-4mm pupil size.

 

Wouldn't worry or even think too much about it, we seem to do a lot of numeric comparisons and still end up nowhere. May I suggest you go down the "without thought or concern" line and forget it? lol.giflol.gif

I do and I worked in optics for 5 years. I can honestly say that "exit pupil" has never come into any stray thought process when buying a scope or binoculars at any time.

 

And at 3.5mm the eye will get just 1/4 the light of the 7mm exit pupil, it is the ratio of the area so the square of the diameters/radaii. So in a way 4x as bad not 2x as bad. grin.gifgrin.gif

 

Forget the numeric comparisons and forget the numeric rules.


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#3 Antonio R.G

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Posted 18 February 2020 - 07:07 AM

I'm a fan of 7x50 binoculars and I have a lot of them in my collection. It's my favorite configuration for all use (and I'm 52). Comfort, ease of use, stability, bright image, simplicity, good build quality ... they are a sum of values ​​that make a binocular good, not just the exit pupil. Also the intended use is important and some configurations offer better results depending of power or the weight and size (astronomy, ornithology, etc.). If I only had one binocular my choice would be 7x50. Anyway, I never think about exit pupil and other similar things when I use one of my best 7x50 (or other configuration). I simply limit myself to enjoy. Theory, numbers and mathematical formulas may be correct, no doubt, but in the end your eyes and your brain (what you really perceive) have the last word. If you try 8x30 against 7x50 and the latter seems much sharper and brighter, pay attention to what your eyes see and forget the theory.
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#4 Corcaroli78

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Posted 18 February 2020 - 08:10 AM

I just recently acquired some old nippon 7x50,s.they are optically excellent. But I was worried about my 50 y o eyes not being compatible with a 7mm e p.i just did a daylight test.i measured my entrance pupil at 3.5mm.i then looked through my 8x30,s which gave me a similar exit pupil.then I looked through the 7x50,s.and the latter were noticeably brighter,even though my entrance pupil was only 3.5mm,and receiving only half the light of the 7x50.perhaps the larger pupil rays are absorbed by peripheral vision?the 7x50 was definitely brighter,

 

 Theory, numbers and mathematical formulas may be correct, no doubt, but in the end your eyes and your brain (what you really perceive) have the last word. If you try 8x30 against 7x50 and the latter seems much sharper and brighter, pay attention to what your eyes see and forget the theory.

 

I agree with the statement of Antonio, let the math aside and find what brings ease of view and visual comfort.  I have binos with 7 mm exit pupil and means nothing at daytime, but they are very relaxing to use. Provide a bright sky? sure, but i can observe more time as i am not forcing my eyes and for people like us with a bad pair of eyes (i am 41), comfort is a must.

 

In my personal experience, if i need to pick one of the two binos you mention, i would take the 7x50 instead the 8x30.

 

Carlos


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#5 ButterFly

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Posted 18 February 2020 - 08:16 AM

The eye pupil is very quick to respond to changes in brightness.  The 3.5mm measurement, unless made while looking through the binos at the target, is meaningless.

 

7x50s are great under dark skies.  It it the brightest 7x view under any conditions (unless your pupil get bigger than 50/7 mm).


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#6 Simcal

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Posted 18 February 2020 - 08:21 AM

There's a chemical for night vision? 

 

.. and with whatever chemical it is that causes better night vision present, 

um.. what is this chemical of which you speak, and where would one acquire it?  bigshock.gif



#7 TOMDEY

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Posted 18 February 2020 - 08:30 AM

Hi, warpsl! In your daytime experiment, the two should deliver equal illuminance, provided your eyes are centered on the pupils. Here are some possibilities that could explain your experience.

 

>the 8x30s might simply transmit less aka lower throughput. Depending on coatings, prisms, etc. this is a possibility.

>your pupils could be expanding when you hold the binos up to your eyes. Daytime pupil adaptation is rapid.

>the 7mm pupils are a breeze to keep filling your eyes' aka plenty of alignment margin. The 3.75mm pupils would start to clip off light if you are even 0.25mm off on IPD and/or eye placement.

>the marginally pupil-matched binos are more likely to vignette toward the field edges.

 

Whatever is going on, it is ultimately explicable. For night time use, the 7x50s should certainly provide a brighter image.   Tom



#8 Jon Isaacs

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Posted 18 February 2020 - 10:47 AM

There's a chemical for night vision? 

 

um.. what is this chemical of which you speak, and where would one acquire it?  bigshock.gif

The chemical is called rhodopsin and it's a pigment in the retina of your eye that is responsible for dark adaption. 

 

https://en.m.wikiped.../wiki/Rhodopsin

 

In any event, I do think about exit pupil when both buying and using eyepieces, telescopes and binoculars. 

 

I do have large dark adapted pupils, closer to 8 mm than to 7mm. Experience has taught me that for some situations, very large exit pupils are desirable but that most of the time, a smaller exit pupil with its higher magnification will show me more..

 

Under dark skies, 10x50s generally show more than 7x50s. 10.5x70s show more than 10x50s and 15x70s show more than 10.5x70s..

 

Jon


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#9 PEterW

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Posted 18 February 2020 - 10:52 AM

The sensitivity improvement with dark adaption is far greater than the area differences in exit pupil, though more light in will mean more chance of seeing things if retinal sensitivity is the same.

Peter
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#10 Simcal

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Posted 18 February 2020 - 11:21 AM

The chemical is called rhodopsin 

Thanks Jon, I learned something new.  waytogo.gif



#11 Rich V.

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Posted 18 February 2020 - 11:30 AM

Perhaps the difference in brightness between the two binoculars can be explained.  

 

All binoculars have some degree of illumination fall off towards the edges of their fields.  With even the best, only the central 40-50% of the FOV is fully illuminated by the entire aperture.  A 7mm exit pupil binocular that is "stopped down" by the eye's 3.5mm entrance pupil will show better illumination across its field than a native 3.5mm exit pupil binocular that's less than half illuminated beyond the central area of the field.  The central 3.5mm of the 7mm exit pupil bino will be in the illumination "sweet spot" so will appear brighter than the smaller, lesser illuminated binocular's exit pupil.

 

Rich


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#12 MartinPond

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Posted 18 February 2020 - 12:57 PM

To get more 'good eye chemicals'  into your eyes,

   (there are multiple chemicals that help, some in

    the receptors and some as regenerative anti-oxidants)

   spinach pie or spinach dip is tasty and effective.

   Better biological absorption than a pricey pill.

 

I started with the pie, but I make a lot of 'dip' now,

   with chopped frozen spinach, sour cream, powdered parmesan,

    garlic, oil, salt, pepper, and fine corn meal.

   The corn meal prevents curdling and thickens so I can 

   dip crackers and eat cold (yum). Otherwise there is a process

    of squeezing and toweling the thawed spinach.

    Collard greens are very good, but chewy.  Kale is excellent,

    but other family members find it bitter. 

 

Most eyes cannot go to 7mm, but having the excess size

   makes it quick and easy to place the eyes, and the 7x power

   is easier for the cortex to track the image and follow any shaking.

   7x50  also makes any eye--2,1--obj  eyepiece have a long eye relief

   for even moderately priced models.

   As compared to, say, 7x35, the 7x50s usually seem brighter to me,

    but I suspect that has to do with eye placement and optical cortex

     tracking  (matching the 2 sides in terms of brightness),

     a 'signal processing' thing.

    The falling-off of brightness hadn't occurred to me,

      but it does happen in most binoculars..

 

The Eurasian standard 8x30 is small and light, but 

     the extra power and the small/light size aggrevate shaking.

     10x50s at least have the extra size/moment-of-inertia 

     improvement over 8x30.  It's great to have  both

     7x50 and 10x50..

 

 

For a bit more power but the same 7mm exit pupil, the

     8x56 size is more rare,  but available.

     It usually is heavier, though.


Edited by MartinPond, 18 February 2020 - 01:07 PM.

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#13 Mr. Bill

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Posted 18 February 2020 - 02:55 PM

Having an exit pupil larger than the eye pupil causes less blackouts when moving the eye to take in the edges of a large fov.


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#14 warpsl

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Posted 18 February 2020 - 03:39 PM

What rich v said is plausable.both binos are 60,s era jap glass with single coatings, but the prisms on the 7x50,s are huge relative to their objectives.

#15 Jon Isaacs

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Posted 18 February 2020 - 03:47 PM

Having an exit pupil larger than the eye pupil causes less blackouts when moving the eye to take in the edges of a large fov.

 

Having an eye pupil larger than the exit pupil also reduces the likely hood of blackouts. 

 

Jon




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