Rifle Scopes What’s the plus of having a bigger tube?

[Glassaholic]

@koshkin Whats the science behind erector zoom ratio affecting exit pupil? As a hunter I enjoy having a large exit pupil at minimum magnification as it helps with quick shots when I am walking around still hunting. Repeatable cheek weld isn’t always a thing when you are standing but leaning under a tree limb while leading an animal and trying to avoid objects with the barrel.

The classic calculation that most fud’s take as the gospel is that objective diameter/magnification = exit pupil, but am I wrong in saying that only holds for 3x erector scopes? (And perhaps 4x? My AMG claims 8.3 at 6x which fits the calculation).

I’ve moved some higher zoom ratio scopes down the road because of my perceived trouble “getting behind” them at low power in awkward shooting positions. For instance, a Swarovski Z8i 2.3-18x56 that I had, 56/2.3 = 24.3, but Swarovski states exit pupil at 2.3x is only 8.1mm. Also moved on from a 5-30x50 Zeiss V6, the classic calculation says 10mm but Zeiss states 9.5mm, which is the same for the 3-18x50 Z6, which to me indicates the limitation on exit pupil exists in the erector?

If I understand what you're saying correctly Chris, I believe what you are experiencing is eyebox rather than exit pupil. You got it right with the diameter of the objective/magnification = exit pupil, that holds true regardless of the erector, for example, a Schmidt 3-27x56 will have the same exit pupil at 16x as the Hensoldt 4-16x56 even though one is using a 4x erector and the other a 9x. Now, how finicky the eyebox is between a given 4x or 8x scope is another question entirely and that's where ILya could probably explain better than I how that relationship works.

 

[ChrisAU]

If I understand what you're saying correctly Chris, I believe what you are experiencing is eyebox rather than exit pupil. You got it right with the diameter of the objective/magnification = exit pupil, that holds true regardless of the erector, for example, a Schmidt 3-27x56 will have the same exit pupil at 16x as the Hensoldt 4-16x56 even though one is using a 4x erector and the other a 9x. Now, how finicky the eyebox is between a given 4x or 8x scope is another question entirely and that's where ILya could probably explain better than I how that relationship works.

I don’t believe we are quite on the same page - I am discussing the scientific gobbledy gook of exit pupil diameter. In other words, if I hold my head at the exact same distance behind the scope, how much can I move my head on a plane keeping the distance constant and maintain a full sight picture.

If the calculation holds true regardless of zoom ratio then why would a Swaro 2-16x50 Z8 have an exit pupil of 8.1mm at 2x instead of 25mm, while a Swaro 2-12x50 Z6 has an exit pupil of 9.6mm at 2x instead of 25mm. As the zoom ratio lowers the exit pupil diameter does grow with a constant zoom value and objective diameter, based on that one example anyway. Meanwhile a Swaro 3-10x42 Z3 has an exit pupil at 3x of 12mm, even with a higher zoom value (3x vs 2x) and smaller objective.

Just something I’ve been wondering about, and a disclaimer is that I am by no means any kind of expert. Just always prescribed to the obj diameter/mag = exit pupil diameter calculation but it obviously doesn’t work on most scopes who publish the specs and definitely shows a tendency to deviate even further as zoom ratio goes up in the erector.

Edit: Forgive typos please, corrected a few, typing on my phone.

 

[koshkin]

@koshkin Whats the science behind erector zoom ratio affecting exit pupil? As a hunter I enjoy having a large exit pupil at minimum magnification as it helps with quick shots when I am walking around still hunting. Repeatable cheek weld isn’t always a thing when you are standing but leaning under a tree limb while leading an animal and trying to avoid objects with the barrel.

The classic calculation that most fud’s take as the gospel is that objective diameter/magnification = exit pupil, but am I wrong in saying that only holds for 3x erector scopes? (And perhaps 4x? My AMG claims 8.3 at 6x which fits the calculation).

I’ve moved some higher zoom ratio scopes down the road because of my perceived trouble “getting behind” them at low power in awkward shooting positions. For instance, a Swarovski Z8i 2.3-18x56 that I had, 56/2.3 = 24.3, but Swarovski states exit pupil at 2.3x is only 8.1mm. Also moved on from a 5-30x50 Zeiss V6, the classic calculation says 10mm but Zeiss states 9.5mm, which is the same for the 3-18x50 Z6, which to me indicates the limitation on exit pupil exists in the erector?

For most scopes, the exit pupil on the low magnification setting is not equal to objective diameter divide by magnification. On low power, you are not using all of the objective.

At higher magnifications, it is. For the Swarovski you mention, on 2.3x, the scope is using only a bit over 18mm of the objective. Exit pupil stays right around 8.1mm until you are around 7x. That is the point where the scope starts utilizing using the entire objective and continues to do so as you go up in power.

With higher erector ratio scopes, the overall system is a lot more complicated: more optical elements are moving with respect to each other as you zoom up and down, so optimizing all of that for a larger exit pupil size is substantially more difficult.

It is not difficult to make large exit pupil on low power, but if it is not optimized right, it will look horrible. It is much easier to have a well optimized large exit pupil on low power with a scope that does not have a very high erector ratio.

This is most observable with low power scopes. Look at the spec table in this piece of 1-8x scopes: http://opticsthoughts.com/?p=2410

Notice than the exit pupil of Nightforce NX8 on 1x stands out as being the smallest. I did not test the NX8 for that article, but got my hands on it for a little bit at a later point. I really like the illumination on that scope and the size, but it is notably harder to get behind for me than with many competing designs. It is not bad, but it is noticeable.

When I looked at the Blaser 1-7x24, I compiled another data set with different scopes:

Blaser Infinity 1-7×28 Riflescope » OpticsThoughts

What I found is that for me, for a LPVO, above 10mm does not make too much difference, but once you start getting below that, I am a little slower getting behind the scope. It may vary rifle to rifle depending on stock fit. I did my experimentation on the same AR for consistency.

One of the reasons you pay a lot more for the ATACR than NX8 is that 1x exit pupil, but ATACR is also measureably longer. That makes it kinda impressive that March almost made it to 10mm with their 1-8x24 Shorty.

I am not awayre of any 1-4x scope that has a 1x exit pupil smaller than 12mm and several were in the 15-16 range.
It is simply easier to design a lower magnification erector scope.

ILya

 

[ChrisAU]

For most scopes, the exit pupil on the low magnification setting is not equal to objective diameter divide by magnification. On low power, you are not using all of the objective.

At higher magnifications, it is. For the Swarovski you mention, on 2.3x, the scope is using only a bit over 18mm of the objective. Exit pupil stays right around 8.1mm until you are around 7x. That is the point where the scope starts utilizing using the entire objective and continues to do so as you go up in power.

With higher erector ratio scopes, the overall system is a lot more complicated: more optical elements are moving with respect to each other as you zoom up and down, so optimizing all of that for a larger exit pupil size is substantially more difficult.

It is not difficult to make large exit pupil on low power, but if it is not optimized right, it will look horrible. It is much easier to have a well optimized large exit pupil on low power with a scope that does not have a very high erector ratio.

This is most observable with low power scopes. Look at the spec table in this piece of 1-8x scopes: http://opticsthoughts.com/?p=2410

Notice than the exit pupil of Nightforce NX8 on 1x stands out as being the smallest. I did not test the NX8 for that article, but got my hands on it for a little bit at a later point. I really like the illumination on that scope and the size, but it is notably harder to get behind for me than with many competing designs. It is not bad, but it is noticeable.

When I looked at the Blaser 1-7x24, I compiled another data set with different scopes:

Blaser Infinity 1-7×28 Riflescope » OpticsThoughts

What I found is that for me, for a LPVO, above 10mm does not make too much difference, but once you start getting below that, I am a little slower getting behind the scope. It may vary rifle to rifle depending on stock fit. I did my experimentation on the same AR for consistency.

One of the reasons you pay a lot more for the ATACR than NX8 is that 1x exit pupil, but ATACR is also measureably longer. That makes it kinda impressive that March almost made it to 10mm with their 1-8x24 Shorty.

I am not awayre of any 1-4x scope that has a 1x exit pupil smaller than 12mm and several were in the 15-16 range.
It is simply easier to design a lower magnification erector scope.

ILya

Thank you for taking the time for that, makes sense. Every google result trying to explain simply says some version of “a scope at 5x with a 50mm scope has an exit pupil of 10mm etc etc” and it just isn’t true and I’ve wondered about it. I think it’s a weakness of high zoom ratio scopes for hunters that isn’t given enough consideration.

 

[koshkin]

Thank you for taking the time for that, makes sense. Every google result trying to explain simply says some version of “a scope at 5x with a 50mm scope has an exit pupil of 10mm etc etc” and it just isn’t true and I’ve wondered about it. I think it’s a weakness of high zoom ratio scopes for hunters that isn’t given enough consideration.

Correct. Usability matters, but noone wants to talk about it.

ILya

 

[Nik H]

That has to be the most valid explanation ive ever heard. I take it you have no idea what you are talking about and just read that on SH or AR15 somewhere...im sorry homie....you are incorrect.

Now light absorbing isnt the only reason, like stated previous generally the big the tube more adjustment...

Im not going to explain how light works in a scope cause you have no idea... good day sir

HAHAHAHAHAHA

You should STFU, take notes and apply same....

I would refrain from saying anymore as it reinforces your shoe size IQ about anything to do with optics

 

[ChrisAU]

Correct. Usability matters, but noone wants to talk about it.

ILya

What would be the correct way to measure exit pupil for a guy without advanced equipment? I have noticed Vortex and Leupold do not publish specs and went and measured the apparent exit pupil at min mag on a few Vortex scopes I have using a caliper and a very imprecise method of holding the caliper near the eyepiece while I held an eye closed to measure with the scope at arms length. I came up with some surprising results using the same method across a handful of scopes.

 

[koshkin]

What would be the correct way to measure exit pupil for a guy without advanced equipment? I have noticed Vortex and Leupold do not publish specs and went and measured the apparent exit pupil at min mag on a few Vortex scopes I have using a caliper and a very imprecise method of holding the caliper near the eyepiece while I held an eye closed to measure with the scope at arms length. I came up with some surprising results using the same method across a handful of scopes.

The flashlight method is the most common, but what you are doing works surprisingly well if you are simply comparing scopes. Keep in mind that this is just one metric and how the roll off toward the edge of the XP behaves makes a difference too.

Also, this will work differently depending on how dilated your eye pupil is.

ILya

 

[phantomskittles]

For most scopes, the exit pupil on the low magnification setting is not equal to objective diameter divide by magnification. On low power, you are not using all of the objective.

At higher magnifications, it is. For the Swarovski you mention, on 2.3x, the scope is using only a bit over 18mm of the objective. Exit pupil stays right around 8.1mm until you are around 7x. That is the point where the scope starts utilizing using the entire objective and continues to do so as you go up in power.

With higher erector ratio scopes, the overall system is a lot more complicated: more optical elements are moving with respect to each other as you zoom up and down, so optimizing all of that for a larger exit pupil size is substantially more difficult.

It is not difficult to make large exit pupil on low power, but if it is not optimized right, it will look horrible. It is much easier to have a well optimized large exit pupil on low power with a scope that does not have a very high erector ratio.

This is most observable with low power scopes. Look at the spec table in this piece of 1-8x scopes: http://opticsthoughts.com/?p=2410

Notice than the exit pupil of Nightforce NX8 on 1x stands out as being the smallest. I did not test the NX8 for that article, but got my hands on it for a little bit at a later point. I really like the illumination on that scope and the size, but it is notably harder to get behind for me than with many competing designs. It is not bad, but it is noticeable.

When I looked at the Blaser 1-7x24, I compiled another data set with different scopes:

Blaser Infinity 1-7×28 Riflescope » OpticsThoughts

What I found is that for me, for a LPVO, above 10mm does not make too much difference, but once you start getting below that, I am a little slower getting behind the scope. It may vary rifle to rifle depending on stock fit. I did my experimentation on the same AR for consistency.

One of the reasons you pay a lot more for the ATACR than NX8 is that 1x exit pupil, but ATACR is also measureably longer. That makes it kinda impressive that March almost made it to 10mm with their 1-8x24 Shorty.

I am not awayre of any 1-4x scope that has a 1x exit pupil smaller than 12mm and several were in the 15-16 range.
It is simply easier to design a lower magnification erector scope.

ILya

Found this interesting and had a thought related to exit pupil and amount of the objective that is used. Is this part of why the 5-25 PMii tunnel? They have the exit pupil at 5x listed as 10.95mm which means it would be using the entire objective lens. I may be thinking about this backwards and it doesn't tunnel because of this but because of it tunneling it has a large exit pupil.

Thanks in advance I always enjoy learning from your posts.

 

[koshkin]

Found this interesting and had a thought related to exit pupil and amount of the objective that is used. Is this part of why the 5-25 PMii tunnel? They have the exit pupil at 5x listed as 10.95mm which means it would be using the entire objective lens. I may be thinking about this backwards and it doesn't tunnel because of this but because of it tunneling it has a large exit pupil.

Thanks in advance I always enjoy learning from your posts.

Exit pupi size and field of view do not have anything to do with each other.

Tunneling is a field of view related phenomenon.

You can put an aperture reducer on the objective lens if you want to test this. You will see exit pupil get smaller, but FOV will not change.

ILya

 

[Glassaholic]

Thank you for taking the time for that, makes sense. Every google result trying to explain simply says some version of “a scope at 5x with a 50mm scope has an exit pupil of 10mm etc etc” and it just isn’t true and I’ve wondered about it. I think it’s a weakness of high zoom ratio scopes for hunters that isn’t given enough consideration.

I fell into the same trap. Learn something new every day. I’m glad you brought this up Chris as it helps us all to understand what an engineer is doing when they are designing an optical formula, and how that plays out with regard to our experience behind the scope. Back to the comments made by the Swarovski guy, he mentioned wasted light with an overly large exit pupil, but then mentions that does allow for some movement - I assume without losing the sight picture.

 

[phantomskittles]

Exit pupi size and field of view do not have anything to do with each other.

Tunneling is a field of view related phenomenon.

You can put an aperture reducer on the objective lens if you want to test this. You will see exit pupil get smaller, but FOV will not change.

ILya

Ok, thanks for the quick reply.

 

[koshkin]

I fell into the same trap. Learn something new every day. I’m glad you brought this up Chris as it helps us all to understand what an engineer is doing when they are designing an optical formula, and how that plays out with regard to our experience behind the scope. Back to the comments made by the Swarovski guy, he mentioned wasted light with an overly large exit pupil, but then mentions that does allow for some movement - I assume without losing the sight picture.

Wasted light is a pretty terrible way to go about describing this, frankly.

It is not a bad idea to let your eye have some freedom to dither within the exit pupil. It helps you see better and cuts down on eye fatigue.

ILya

 

[Glassaholic]

Scopes are stronger with a 34mm tube so it doubles as a hammer. NF has a vidya on this. The ATACR serves double duty when I lose my hammer.

10/10, would buy a second to duel wield hammers.

You'd be at a disadvantage if someone came at you with a US Optics (aka the baseball bat)

 

[Glassaholic]

Wasted light is a pretty terrible way to go about describing this, frankly.

It is not a bad idea to let your eye have some freedom to dither within the exit pupil. It helps you see better and cuts down on eye fatigue.

ILya

Eye fatigue, eyebox, exit pupil, they all have a relationship with how the scope delivers light. Would love to see one of your videos to explain a little more how they are all related, but no rush, we can wait until you get your whiteboard back

 

[davere]

What make him "The Optics" guy? Explain that to me? Heres the thing.... i could care less about "last long around here" i simply disagree with the invaild statement... but anywho

Ilya's an optical engineer by trade, and if you bothered to spend even a couple minutes looking at anything on this forum, you'd not only find that fact out, but you'd also discover that the dude has spent a lot of his free time publishing a lot of useful information about optical systems and rifle scopes in particular... all for free.

Tube diameter (above a certain minimum size - and I don't know what that size is for modern scopes) has nothing to do with "light gathering" in the scope. You're looking at a balance between the front element size and the scope's magnification, as others have pointed out.

In photographic lenses, the design goals are different, but the same things apply. The aperture is effectively the tube diameter limitation, and the focal length is effectively the magnification (though not exactly) - and the exit pupil has a far larger minimum size (approximately 43mm for a full frame 35mm camera system). In order to design a lens that provides a certain focal length at a certain aperture, the lens has to accommodate both the physical size of the aperture itself and associated control system, and the (sometimes much) larger size of the front element required to not shadow the aperture. Lens coatings and lens glass composition have a lot to do with light transmission within the lenses, and therefore apparent "brightness".

 

[koshkin]

Scopes are stronger with a 34mm tube so it doubles as a hammer. NF has a vidya on this. The ATACR serves double duty when I lose my hammer.

10/10, would buy a second to duel wield hammers.

A larger diameter tube, if made with the same wall thickness, is stiffer, but less resistant to deformation if memory serves me right. A thicker wall will make it more resistant to deformation and stiffer yet, but then you lose some of the real estate you got by going to a larger tube.

As always, everything is a compromise.

ILya

 

[koshkin]

Eye fatigue, eyebox, exit pupil, they all have a relationship with how the scope delivers light. Would love to see one of your videos to explain a little more how they are all related, but no rush, we can wait until you get your whiteboard back

What other topics should I address when my life settles back down a little again?

Future Video and Article Ideas? » OpticsThoughts

ILya

 

[7WSMShooter]

Well this thread took a turn for the FUNNY! ;D

Hoping to God @Mike_Pancake goes full on Budly up in this!

We need another full on Buddly thread. I need a good laugh.

 

[Glassaholic]

What other topics should I address when my life settles back down a little again?

Future Video and Article Ideas? » OpticsThoughts

ILya

I'd love to see you address the new Nightforce NX8's and the Burris XTR III's

 

[YF12A]

Looking forward to this as well.

 

[SRPowah]

That has to be the most valid explanation ive ever heard. I take it you have no idea what you are talking about and just read that on SH or AR15 somewhere...im sorry homie....you are incorrect.

Im not going to explain how light works in a scope cause you have no idea... good day sir

Considering this was in response to Koshkin, can we ban this homie for this sentence alone?

 

[SnowMan]

My bicycle has an inner tube. Sometimes the sun gets in my eyes, Is that the same thing?

 

[koshkin]

I'd love to see you address the new Nightforce NX8's and the Burris XTR III's

I will later in the year.

ILya

 

[JakeM]

Well this thread took a turn for the FUNNY! ;D

Hoping to God @Mike_Pancake goes full on Budly up in this!

Hell, he could be Buddly with a new name.

 

[YF12A]

How about MrPancake? Seriously, if this guy thinks he knows everything about rifle and camera and optics in general at all, he ought to look into "amateur astronomy". Decades ago, the money I spent would have paid for a batch of Tangent Thetas now. A great optics learning experience and I got to see many great Comets and other events. When I got to look at the Rings of Saturn for the first time with my own eyes it sent chills up my spine!

Now I feel we are blessed to have people like Ilya and others to pass on knowledge and testing that I don't have the experience or wallet to do as I gradually go from a 100yd bench shooter to L/R. Thanks to all.

 

[Glassaholic]

Hell, he could be Buddly with a new name.

I think that Budly thread and his Quigley Ford optics or whatever those were called should be stickied, it took me a few months with everyone mentioning Budly to actually look it up and find out what that was all about, I must say it was quite entertaining but I fear the guy might have had a stroke or something with how some responded.

With regard to Mr. Pancake, I've noticed you have not responded for a while now, you may have dropped off the forum for all I know, but if you're still on, don't take the responses and jabs personally, you came in as a newb and made some pretty bold statements that couldn't be backed up, evidence was brought forth to show this was the case, if you take time to evaluate what you've said and how you've responded and can admit you were wrong, no hard feelings. Seriously, this community may be a bit harsh and gruff at times, but overall it's a great community and soon this will be behind you. Heck, I've been on here for years and have had my own share of "stupid" stuff that I've said, and often times I've been corrected by those who know more than me and yes, it's embarrassing at times, but it's how we learn and grow.

 

[SRPowah]

With regard to Mr. Pancake, I've noticed you have not responded for a while now, you may have dropped off the forum for all I know, but if you're still on, don't take the responses and jabs personally, you came in as a newb and made some pretty bold statements that couldn't be backed up, evidence was brought forth to show this was the case, if you take time to evaluate what you've said and how you've responded and can admit you were wrong, no hard feelings. Seriously, this community may be a bit harsh and gruff at times, but overall it's a great community and soon this will be behind you. Heck, I've been on here for years and have had my own share of "stupid" stuff that I've said, and often times I've been corrected by those who know more than me and yes, it's embarrassing at times, but it's how we learn and grow.

Ok, its one thing to say something stupid and learn from it, especially when its something that has changed over time. I have made that mistake. Its a whole other game when you state something factually wrong and then insult everyone that tries to correct you, including the one guy that could factually answer it better than arguably anyone else on this forum. That is straight up Buddly quality thinking.

 

[Glassaholic]

Ok, its one thing to say something stupid and learn from it, especially when its something that has changed over time. I have made that mistake. Its a whole other game when you state something factually wrong and then insult everyone that tries to correct you, including the one guy that could factually answer it better than arguably anyone else on this forum. That is straight up Buddly quality thinking.

Or young arrogance - the know it all attitude before they realize they don't know it all

 

[hk dave]

Ok, its one thing to say something stupid and learn from it, especially when its something that has changed over time. I have made that mistake. Its a whole other game when you state something factually wrong and then insult everyone that tries to correct you, including the one guy that could factually answer it better than arguably anyone else on this forum. That is straight up Buddly quality thinking.

Well at least he didn’t talking about how he’ll tear people new bungholes and that he’s a real bad muther that benched 275!

God I miss Budly.

 

[notorious]

Heck, I've been on here for years and have had my own share of "stupid" stuff that I've said, and often times I've been corrected by those who know more than me and yes, it's embarrassing at times, but it's how we learn and grow.

Humility is a wonderful attribute. I get to exhibit mine often.

 

[JakeM]

I don't think mike learned anything. He hasn't replied saying he could be wrong, or backing up his point any more.

 

[Franko]

What other topics should I address when my life settles back down a little again?

Future Video and Article Ideas? » OpticsThoughts

ILya

I'm not an optics expert and won't ever be one. However I am an optics consumer. Perhaps a series on "how to be a better buyer of optics".

You could address topics like; What features matter for what applications. How to tell a good optic from a mediocre one. Where the thresholds for diminishing returns lie (sure a 34mm tube is bigger than a 30mm but is it better, and if so when, and by how much?).

 

[BANG...ping]

This is false. Don’t spread misinformation.

On a camera the F stop increases and decreases the aperture size to control the amount of light that the camera records. Please explain how tube size is irrelevant.
Bang

 

[koshkin]

On a camera the F stop increases and decreases the aperture size to control the amount of light that the camera records. Please explain how tube size is irrelevant.
Bang

In a rifle scope, the equivalent of what you are calling F-stop is the diameter of the objective lens.

ILya

 

[SRPowah]

On a camera the F stop increases and decreases the aperture size to control the amount of light that the camera records. Please explain how tube size is irrelevant.
Bang

BANG...miss

 

[Carlos0311B4]

Where did he go? George?! Where did he go?!

 

[hk dave]

BANG...miss

You sir just won the internet. Lol

 

[Steel head]

I’ve been seeing a lot of the approach from new members that is the aggressive, “I’m dominant” approach to the forum. Make definitive statements about stuff you only know a little about or have read about in the internet and don’t back down no matter what. Double down on your ignorant statements and belittle all who try to point you in the right direction so as to make sure that they know you are an alpha male who knows everything. Then whine and cry or attack anyone who decides they’ve had enough of your immature bullshit and call them names, ‘cause, you know...you’re immature.

Lol
I was a noob here once.
I quickly found out how ignorant I was.

I decided to learn rather than be a twat.

 

[Currycure]

there is also better light transmission through the 30mm tube. same concept as objective lenses. the larger the objective lens, the more light it allows to pass. i've found that with a scope with a 40mm objective lens with a 1" tube vs. a scope with a 50mm objective lens and a 30mm tube the latter will allow you to see your target for up to 45 minutes longer during the hours of dawn and dusk. ie, 45 minutes earlier in the morning and 45 minutes later in the evening.

 

[koshkin]

This has got to be the same troll with different logins.

ILya

 

[goosed]

Lol
I was a noob here once.
I quickly found out how ignorant I was.

I decided to learn rather than be a twat.

Wait... what... not a twat??? since when???

 

[hk dave]

there is also better light transmission through the 30mm tube. same concept as objective lenses. the larger the objective lens, the more light it allows to pass. i've found that with a scope with a 40mm objective lens with a 1" tube vs. a scope with a 50mm objective lens and a 30mm tube the latter will allow you to see your target for up to 45 minutes longer during the hours of dawn and dusk. ie, 45 minutes earlier in the morning and 45 minutes later in the evening.

That’s not how it works.

 

[Pusher591]

That has to be the most valid explanation ive ever heard. I take it you have no idea what you are talking about and just read that on SH or AR15 somewhere...im sorry homie....you are incorrect.

Now light absorbing isnt the only reason, like stated previous generally the big the tube more adjustment...

Im not going to explain how light works in a scope cause you have no idea... good day sir

Hahahaha dude, do you realize who you just said that to? You may want to do some checking on his credibility before you just make blind statements.

 

[Glassaholic]

there is also better light transmission through the 30mm tube. same concept as objective lenses. the larger the objective lens, the more light it allows to pass. i've found that with a scope with a 40mm objective lens with a 1" tube vs. a scope with a 50mm objective lens and a 30mm tube the latter will allow you to see your target for up to 45 minutes longer during the hours of dawn and dusk. ie, 45 minutes earlier in the morning and 45 minutes later in the evening.

Where did you learn this? Is it just an assumption you are making or did you learn this in school or? Given your scenario above, do you think it is possible that the greater longevity in lower light situations might be due to the 50mm objective vs. the 40mm objective? Yes, it may "seem" like a larger tube would allow more light through; however, this is not how a riflescope is designed to function. Don't believe us, call up any "good" riflescope manufacturer and ask to speak to an engineer and let them explain. I posted an article earlier from Swarovski, here is another from Leupold - https://www.leupold.com/leupold-core/core-knowledge/articles/top-5-optics-myths-explained

MYTH - A LARGER MAINTUBE LETS IN MORE LIGHT AND MAKES FOR A BRIGHTER SCOPE​

On the surface, this seems like it makes sense. If you had a 2-foot diameter water pipe vs. a 1-foot diameter pipe, the 2 foot one is going to let more water through. But light is a weird thing, and there’s more going on inside your rifle scope than you may think...​

​

The little-known fact is that it’s the erector system that limits how much light is getting to your eye. It also has a big effect on image quality.​

Using the water example above, think of it like this, if you turn on a fireman's hose you're going to have a lot of water gushing out right, but if you hooked up your garden hose to the fireman's hose you're going to constrict the flow of water right? This is how you're thinking with the statement above and you're wondering how on earth can a smaller hose diameter handle that flow of water, but consider this, let's put a nozzle on that fireman's hose and that nozzle allows for a 1/2" stream of water that is blasting out an incredible amount under pressure, and let's say you could connect your 3/4" garden hose in perfect alignment and let's just say gravity and other effects would not hinder the trajectory of this stream, what would happen? Well that stream of water would pass right through your garden hose unhindered. In a similar fashion that is what is happening to the light through the riflescope, the front objective is the source for bringing in the amount of light, but the rest of the optical system is redirecting and focusing that light similar to how the nozzle works in the example above. Yes, you do need a diameter that will allow enough light to pass through to be effective based on how much light your eye can handle (the Swarovski article explains a little about how much the average eye can handle during the day and in low light). Optical engineers understand this which is why we do not see scopes with 50mm maintubes or larger, it would be a waste of material and cost to do so when the reality is they wouldn't be able to get "more light" out of this design than another manufacturer can out of a good 30mm design.

I understand this might be a difficult concept to understand, but hopefully this helps. And if you simply refuse to believe us and every optical engineer out there, that is fine too, but maybe this is not the forum for you.

 

[Ledzep]

So the smaller tube has better light transmission then?

 

[notorious]

 

[Langford]

I love IOR Scopes because if their 40mm tube, lets much more light through.

 

[goosed]

I love IOR Scopes because if their 40mm tube, lets much more light through.

Way too obvious buddly...

 

[beetroot]

Way too obvious buddly...

Some folk have the knack for trolling, others no so.