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10X42 vs 10X50

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Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/26/2016 at 14:32
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Originally posted by vortech347 vortech347 wrote:

A great topic and conversation.

If I'm way off base just say so.  In a very simplistic way, isn't it similar to lumens vs. Lux with flashlights.

One is total amount of light and one is intensity.

So you have 90% light transmission through the glass.  With a certain exit pupil size you could calculate the total amount of light being transmitted through the objective.

Increase that exit pupil size with the same transmission efficiency and the total amount of light passing through to the objective is greater.

Now, if your eye's pupil is only dilated to 3mm and your binocular has a 5mm exit pupil, you most likely won't see much difference compared to a binocular with the same 90% light transmission but only has a 3mm exit pupil.

BUT, your eyebox could be more forgiving since you have some margin of error for eye placement.

Here is an example I've personally experienced.

I have Nikon Monarch ATB 10x32's and a buddy has Leica 10x50 Ultravids.  In bright daylight the images are fairly comparable between the two.  The image is nicer through the Leicas but both are bright and clear and it's easy to view wildlife through either.

Now let's move to dusk.  The Leica's keep looking great while the Nikon get's dimmer and dimmer much faster.  It was truly night/day difference at sunset looking through both.

In that case I suspect both light transmission AND exit pupil both played roles in showing the drastic difference in quality between the two binoculars.  

Sound reasonable?

Way off base. 

somewhere on this site is a pretty good discussion of light transmission through a scope, I just don't have time to look for it right now... but the OBJECTIVE is the beginning point, the OCULAR, where EXIT PUPIL exists, receives the transmitted light... the last surface before impacting the eye.


Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/26/2016 at 14:59
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A while back I wrote a lengthy and wordy article I called Riflescope Fundamentals.  The section on optical quality is relevant to binoculars and talks a little about light transmission:


A couple of other things that came up in this thread while skimming through it that I do no think I addressed in that article:

If the exit pupil of the binocular is larger than your eyepupil, your eye naturally moves a little within the exit pupil and gives you better image fidelity.  If your eye pupil is 3mm and the exit pupil of the binocular is also 3mm, it will look a little worse than an otherwise identical binocular that gives your a 4mm or greater exit pupil at the same magnification.

When it gets dark and your eye pupil dilates, the imaging performance of your eye drops a little, since its effective F/# changes.

The overall amount of light scales with the square of the diameter: as far as total amount of light goes, a 50mm objective delivers 41.7% more light overall than a 42mm objective, assuming the same transmission ratios.  That does not mean that the image will look 40% better.  Image perception is complicated.

Now, on light transmission: there is a standardized way of measuring it.  For a few years I used to make customized equipment that did just that for a variety of electro-optical devices (and MTF stations, camera testers, night vision testers, spectral projectors, spectroradiometers, etc).  What is not standardized, is how that information is used in marketing materials. 

If you want to measure light transmission of optical devices in the Vis/NIR range, this is is the simpelst way to go:
Calibrated detector: https://www.newport.com/p/1936-R

These two plus some mechanics get you a calibrated, industry standard transmission tester for optical systems.  I am pretty sure I still have one of these mothballed somewhere.  When I first started looking at scopes, I used it on a bunch of riflescopes.

ILya
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/26/2016 at 15:39
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Originally posted by koshkin koshkin wrote:

A while back I wrote a lengthy and wordy article I called Riflescope Fundamentals.  The section on optical quality is relevant to binoculars and talks a little about light transmission:


A couple of other things that came up in this thread while skimming through it that I do no think I addressed in that article:

If the exit pupil of the binocular is larger than your eyepupil, your eye naturally moves a little within the exit pupil and gives you better image fidelity.  If your eye pupil is 3mm and the exit pupil of the binocular is also 3mm, it will look a little worse than an otherwise identical binocular that gives your a 4mm or greater exit pupil at the same magnification.

When it gets dark and your eye pupil dilates, the imaging performance of your eye drops a little, since its effective F/# changes.

The overall amount of light scales with the square of the diameter: as far as total amount of light goes, a 50mm objective delivers 41.7% more light overall than a 42mm objective, assuming the same transmission ratios.  That does not mean that the image will look 40% better.  Image perception is complicated.



This is perhaps a stupid question but... why is diameter used in scaling light transmission instead of area?  Also, 41.7% is mentioned but I am not sure where that number is coming from.  Am I missing an obvious calculation?  I keep finding a figure in the 30 percent range when squaring objective or exit pupil.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/26/2016 at 15:49
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The diameter is inextricably connected to the surface area. And since the aperture has been used by engineers, and professional optical specialists, for decades, it just makes sense not to reinvent the wheel.

PS BrockSW: How many smokestacks did RMS Titanic have? I am asking for a reason.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/26/2016 at 16:15
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Originally posted by WJC WJC wrote:

The diameter is inextricably connected to the surface area. And since the aperture has been used by engineers, and professional optical specialists, for decades, it just makes sense not to reinvent the wheel.

PS BrockSW: How many smokestacks did RMS Titanic have? I am asking for a reason.


I see what you mean about proportional relationships between diameter and area...no matter how you run the numbers, using area or diameter, the percentages remain the same.

That was a stupid question on my part...however, I'd still like to know where he got the 41% number.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/26/2016 at 16:20
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Originally posted by Brocksw Brocksw wrote:

Originally posted by koshkin koshkin wrote:

A while back I wrote a lengthy and wordy article I called Riflescope Fundamentals.  The section on optical quality is relevant to binoculars and talks a little about light transmission:


A couple of other things that came up in this thread while skimming through it that I do no think I addressed in that article:

If the exit pupil of the binocular is larger than your eyepupil, your eye naturally moves a little within the exit pupil and gives you better image fidelity.  If your eye pupil is 3mm and the exit pupil of the binocular is also 3mm, it will look a little worse than an otherwise identical binocular that gives your a 4mm or greater exit pupil at the same magnification.

When it gets dark and your eye pupil dilates, the imaging performance of your eye drops a little, since its effective F/# changes.

The overall amount of light scales with the square of the diameter: as far as total amount of light goes, a 50mm objective delivers 41.7% more light overall than a 42mm objective, assuming the same transmission ratios.  That does not mean that the image will look 40% better.  Image perception is complicated.



This is perhaps a stupid question but... why is diameter used in scaling light transmission instead of area?  Also, 41.7% is mentioned but I am not sure where that number is coming from.  Am I missing an obvious calculation?  I keep finding a figure in the 30 percent range when squaring objective or exit pupil.

The square of the diameter scales linearly with area.

(50/42)^2=1.41723356 which rounds to a ratio of 1.417 or 41.7% increase. 

ILya
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/26/2016 at 16:21
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I haven't found a need to research that. However, if you will answer my question, I think a bit more will be opened to you.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/26/2016 at 16:22
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Originally posted by Brocksw Brocksw wrote:

Originally posted by WJC WJC wrote:

The diameter is inextricably connected to the surface area. And since the aperture has been used by engineers, and professional optical specialists, for decades, it just makes sense not to reinvent the wheel.

PS BrockSW: How many smokestacks did RMS Titanic have? I am asking for a reason.


I see what you mean about proportional relationships between diameter and area...no matter how you run the numbers, using area or diameter, the percentages remain the same.

That was a stupid question on my part...however, I'd still like to know where he got the 41% number.

If you use the diameter, the percentages are not the same as when using area.

When you use the square of the diameter, they are.

ILya
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/26/2016 at 16:26
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Ilya:

I said "inextricably connected," not the same; just sayin'.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/26/2016 at 16:38
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Originally posted by WJC WJC wrote:

Ilya:

I said "inextricably connected," not the same; just sayin'.

Bill, I know you are on to of this.  My post was mostly a clarification for the original poster's benefit.

ILya
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/26/2016 at 17:04
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Sorry I meant ocular in my post.  

Originally posted by Kickboxer Kickboxer wrote:

Originally posted by vortech347 vortech347 wrote:

A great topic and conversation.

If I'm way off base just say so.  In a very simplistic way, isn't it similar to lumens vs. Lux with flashlights.

One is total amount of light and one is intensity.

So you have 90% light transmission through the glass.  With a certain exit pupil size you could calculate the total amount of light being transmitted through the objective.

Increase that exit pupil size with the same transmission efficiency and the total amount of light passing through to the objective is greater.

Now, if your eye's pupil is only dilated to 3mm and your binocular has a 5mm exit pupil, you most likely won't see much difference compared to a binocular with the same 90% light transmission but only has a 3mm exit pupil.

BUT, your eyebox could be more forgiving since you have some margin of error for eye placement.

Here is an example I've personally experienced.

I have Nikon Monarch ATB 10x32's and a buddy has Leica 10x50 Ultravids.  In bright daylight the images are fairly comparable between the two.  The image is nicer through the Leicas but both are bright and clear and it's easy to view wildlife through either.

Now let's move to dusk.  The Leica's keep looking great while the Nikon get's dimmer and dimmer much faster.  It was truly night/day difference at sunset looking through both.

In that case I suspect both light transmission AND exit pupil both played roles in showing the drastic difference in quality between the two binoculars.  

Sound reasonable?

Way off base. 

somewhere on this site is a pretty good discussion of light transmission through a scope, I just don't have time to look for it right now... but the OBJECTIVE is the beginning point, the OCULAR, where EXIT PUPIL exists, receives the transmitted light... the last surface before impacting the eye.


Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/26/2016 at 17:05
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Ilya:

Are you a Zemax user?
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/26/2016 at 17:22
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Originally posted by vortech347 vortech347 wrote:

Sorry I meant ocular in my post.  

Originally posted by Kickboxer Kickboxer wrote:

Originally posted by vortech347 vortech347 wrote:

A great topic and conversation.

If I'm way off base just say so.  In a very simplistic way, isn't it similar to lumens vs. Lux with flashlights.

One is total amount of light and one is intensity.

So you have 90% light transmission through the glass.  With a certain exit pupil size you could calculate the total amount of light being transmitted through the objective.

Increase that exit pupil size with the same transmission efficiency and the total amount of light passing through to the objective is greater.

Now, if your eye's pupil is only dilated to 3mm and your binocular has a 5mm exit pupil, you most likely won't see much difference compared to a binocular with the same 90% light transmission but only has a 3mm exit pupil.

BUT, your eyebox could be more forgiving since you have some margin of error for eye placement.

Here is an example I've personally experienced.

I have Nikon Monarch ATB 10x32's and a buddy has Leica 10x50 Ultravids.  In bright daylight the images are fairly comparable between the two.  The image is nicer through the Leicas but both are bright and clear and it's easy to view wildlife through either.

Now let's move to dusk.  The Leica's keep looking great while the Nikon get's dimmer and dimmer much faster.  It was truly night/day difference at sunset looking through both.

In that case I suspect both light transmission AND exit pupil both played roles in showing the drastic difference in quality between the two binoculars.  

Sound reasonable?

Way off base. 

somewhere on this site is a pretty good discussion of light transmission through a scope, I just don't have time to look for it right now... but the OBJECTIVE is the beginning point, the OCULAR, where EXIT PUPIL exists, receives the transmitted light... the last surface before impacting the eye.



THank you for clarifying… I hoped that was the case...
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/26/2016 at 23:03
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Originally posted by WJC WJC wrote:

Ilya:

Are you a Zemax user?


Not for a long time now.

My field of expertise is more on the side of image sensors, multispectral imaging systems, targeting pods, etc.

ILya
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/27/2016 at 04:18
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Originally posted by koshkin koshkin wrote:

Originally posted by WJC WJC wrote:

Ilya:

Are you a Zemax user?


Not for a long time now.

My field of expertise is more on the side of image sensors, multispectral imaging systems, targeting pods, etc.

ILya

PM me your email address.  I have something for you to look at.

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