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Help resolving potential issue with UV 8x42HD+

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Old Tuesday 20th August 2019, 18:39   #26
Binastro
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Pies are round (:

Unnecessary to introduce pi.

40+2 squared is 1604+160= 1764.
32 squared is 1024.

1764 divided by 1024 is about 1723 divided by 1000, so about 72%.
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Old Tuesday 20th August 2019, 18:47   #27
dipped
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Quote:
Originally Posted by Binastro View Post
Pies are round (:

Unnecessary to introduce pi.

40+2 squared is 1604+160= 1764.
32 squared is 1024.

1764 divided by 1024 is about 1723 divided by 1000, so about 72%.
So you're working on the principle of square exit pupils?

Am I missing something here, as the last time I checked my binoculars I saw a round (circular) exit pupil.
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Old Tuesday 20th August 2019, 18:54   #28
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What has not been discussed, and which has far greater impact than exit pupils and eye pupils is dark adaptation.

This varies with great complexity.
It depends on age, and on whether one has been in bright sunshine or dull conditions during the previous day.
It depends on health and medication. Antibiotics and numerous medicines affect eye sensitivity.

When twilight and night descend then the chemical effects in our eyes take over.
So switching between binoculars as one dark adapts can give incorrect results.
So can exposure on and off to a light.

When dark adapted, merely looking at a bright object such as Jupiter changes the eye condition.
One can be convinced by comparison, even though actually we are interpreting things wrongly.

Places like the National Physics laboratory in the U.K. and in many other countries carry out tests to set standards. These are accurate unless mistakes are made.
I have had accurate transmission tests carried out by Imperial College and a University lab in Finland and the lab technicians presumably know their jobs.

Individuals using non standard methods and not properly trained will probably not give calibrated results.

As to advertised transmissions. This can be peak transmission or averaged or anything.

Regards,
B.
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Old Tuesday 20th August 2019, 18:54   #29
Mark9473
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Quote:
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Pi x Radius squared gives area so 3.14x4 for 32mm gives 12.56 and so on...
and 3.14 x 2.625 x 2.625 = 21.65
and 21.65 / 12.56 = 1.72 just like I said...
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Old Tuesday 20th August 2019, 18:58   #30
Binastro
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Dipped,

As both exit pupils are round, the only variable is 42 and 32.
Or for area the ratio between 42 squared and 32 squared.

Pi just cancels out.

Regards,
B.

P.S.

Pi r(a) squared divided by Pi r(b) squared is the same as

r(a) squared divided by r(b) squared.

Pi divided by Pi is 1.

Last edited by Binastro : Tuesday 20th August 2019 at 19:08.
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Old Tuesday 20th August 2019, 19:37   #31
dipped
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and 3.14 x 2.625 x 2.625 = 21.65
and 21.65 / 12.56 = 1.72 just like I said...
Hi Mark

Apologies - I worked out my %age increase incorrectly.

I agree with you though I would express the increases as 172% and 142% respectively.
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Old Tuesday 20th August 2019, 19:39   #32
Mark9473
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No it's not a 172% increase. Starting from 1, you have a 72% increase going to 1.72.
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Old Tuesday 20th August 2019, 21:44   #33
John A Roberts
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To pick up on Binastro's point in post #30 . . .

While the standard formula to calculate the area of a circle produces an exact result, for most to use it requires a calculator of some sort

And while that’s not a big deal with the proliferation of hand held digital devices, there is a much simpler way to calculate the relative area of two or more circles
- just square the diameter

That is, eliminate Pi as it’s a constant, and don’t bother to divide the diameter before squaring it
It's a good technique for when you have to use your own embedded device

Leica uses this simplified calculation in it’s manuals for the relative area of exit pupils, where it’s called Geometric Light Value
And it works equally well to compare the relative area of objectives


John
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Old Tuesday 20th August 2019, 23:31   #34
tenex
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When I look at movies with young actors, the pupils are often huge, sometimes up to 9mm.
Maybe they're just very interested in one another? ...Which raises a question, does loving birds improve the performance of one's binoculars?
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Old Wednesday 21st August 2019, 07:42   #35
Mike F
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To pick up on Binastro's point in post #30 . . .

While the standard formula to calculate the area of a circle produces an exact result, for most to use it requires a calculator of some sort

And while thats not a big deal with the proliferation of hand held digital devices, there is a much simpler way to calculate the relative area of two or more circles
- just square the diameter

That is, eliminate Pi as its a constant, and dont bother to divide the diameter before squaring it
It's a good technique for when you have to use your own embedded device

Leica uses this simplified calculation in its manuals for the relative area of exit pupils, where its called Geometric Light Value
And it works equally well to compare the relative area of objectives


John
Thanks for this, John. Very helpful!
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Old Wednesday 21st August 2019, 12:13   #36
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Hi Mark

Apologies - I worked out my %age increase incorrectly.

I agree with you though I would express the increases as 172% and 142% respectively.
Mark is correct because we are talking about the extent of the increase.

A 100% increase would mean double the starting point, because you start from the existing 100% so an increase of 100% takes you to 200%.
A 172% increase would mean double plus another 72% on top or 272% of where you started.

In your case the increase is 'only' 72%.

Lee

Last edited by Troubador : Wednesday 21st August 2019 at 15:51.
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Old Wednesday 21st August 2019, 16:29   #37
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My head hurts....
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Old Wednesday 21st August 2019, 16:38   #38
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I always find a 5mm ep a more comfortable viewing experience than a 4mm whatever the light conditions, and that increased comfort makes me choose the 42mm more often than not. I`v learned to never undervalue a comfortable view.
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Old Wednesday 21st August 2019, 18:29   #39
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Moose8,

Try using the 8X42 for a while (say a week) without the 8X32, then go back to the 8X32.

I am also in agreement with the aforementioned opinion of a 5mm ep, unless it is a good porro prism glass.

Andy W.
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Old Wednesday 21st August 2019, 18:44   #40
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My head hurts....
Time to get those HTs collimated James.

Lee
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Old Thursday 22nd August 2019, 00:51   #41
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Moose: Welcome to Birdforum, as just mentioned above, you need to spend some time with your
new Leica to get acquainted. That means more than just a few quick looks in the evening.

Usually it takes days or weeks to get used to a binocular, how it handles and how to adjust it to your
best use. That means in all conditions, early, daytime and in varying light conditions.

So, don't be hasty in your evaluation, it does take time. Then you will know how you like it.
Good luck, Leica makes some very good optics.

Jerry
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Old Thursday 22nd August 2019, 04:17   #42
chill6x6
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Quote:
Originally Posted by dries1 View Post
Moose8,

Try using the 8X42 for a while (say a week) without the 8X32, then go back to the 8X32.

I am also in agreement with the aforementioned opinion of a 5mm ep, unless it is a good porro prism glass.

Andy W.
Quote:
Originally Posted by NDhunter View Post
Moose: Welcome to Birdforum, as just mentioned above, you need to spend some time with your
new Leica to get acquainted. That means more than just a few quick looks in the evening.

Usually it takes days or weeks to get used to a binocular, how it handles and how to adjust it to your
best use. That means in all conditions, early, daytime and in varying light conditions.

So, don't be hasty in your evaluation, it does take time. Then you will know how you like it.
Good luck, Leica makes some very good optics.

Jerry
^^^^^^
This!
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Old Saturday 24th August 2019, 16:00   #43
Moose8
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Thanks for all the responses! A brief update after having spent a bit more time with the 8x42's-

I think initially I wasn't really distinguishing the forest from the trees, so to speak. In my evening viewing I was so focused on what small details that I couldn't see with the 8x32's that I could with the 8x42's (and not coming up with much) that I wasn't appreciating that as far as overall image and subjective impression is concerned, the 8x42's are presenting a brighter image. I'd still classify the difference in brightness as subtle, but at least noticeable now, if I'm not specifically overthinking it when viewing.

As for if this warrants owning both pairs, I can't say yet. Still need to use them a bit more to appreciate other differences besides brightness.
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