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

pyplynr

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I always thought that the bigger the tube the more adjustment was available for elevation/ windage. But looking at the new NX8 4-32-50 with a 30mm tube it has 26.2 mills of elevation and the gen 2 Vortex 4.5-27x56 with a 34mm tube has roughly the same. What is the upside to a bigger main tube? Trying to decide which one to get.
 

gconnoyer

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Get the scope you like better. Whether it be the reticle, features, etc. I would go with the NF myself over the Razor, but they're two totally different optics at totally different prices. Compare the specs and go from there.

95% of scopes these days will have more adjustment than you will ever need.
After zeroing on my rifle, my Tangent has over 25mil left. I'm never going to shoot my 6mm 1800+ yards.
 
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bschneiderheinze

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I don’t know about the Nightforce but I have a Vortex AMG with a 30mm tube and a new Razor 7c. I can run the razor on 20x on a barricade and the field of view is good enough you don’t even notice it. My son runs the AMG on around 12-14
 
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Surfingsk8r

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I don't have any of the factual data behind the following but these are the reasons I have heard for a larger tube.

Easier to build out an erector that has more travel because there is more space.

Larger field of view (this may be bullshit, I honestly don't know, feel free to correct this and tell me I am wrong)

Larger tube can be thicker and therefor stronger.

Like I said. I don't have any factual data behind any of this it's just the things I have heard.
 

phlegm

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I don't have any of the factual data behind the following but these are the reasons I have heard for a larger tube.

Easier to build out an erector that has more travel because there is more space.

Larger field of view (this may be bullshit, I honestly don't know, feel free to correct this and tell me I am wrong)

Larger tube can be thicker and therefor stronger.

Like I said. I don't have any factual data behind any of this it's just the things I have heard.

You are correct, though a larger field of view is only theoretically possible, not guaranteed. FOV is very dependent on optical design.
 

Sdvldog1371

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A Broader field of view at magnification is what I've been told by countless optics sales people. The Vortex Razor AMG with its 3Omm tube has the same elevation as the 34mm razor gen 2 and the AMG has a slightly wider field of view at magnification. It's also almost 20 ounces lighter.
 

koshkin

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Scope tube diameter comes up a lot and somehow it never gets explained completely. I did a couple of videos that touched on this, I think, but I maybe I should do one focusing on what you get with a larger tube when I get my whiteboard back.

In a nutshell, a larger tube give you the real estate to combine wide FOV, large adjustment range and large zoom ratio.

One of the reasons AMG get good FOV with a 30mm tube is that it is a 4x erector, vs 6x erector on Gen 2. There are some other consideration potentially in play, like DOF, etc. For example, with the March-FX or Nightforce NX8, they are getting wide zoom ration, decent FOV and a lot of adjustment in a 30mm tube by using a very short objective lens system which makes parallax touchier and depth of field more shallow.

I think I touched on this subject in this video:

ILya
 

Moose

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    Scope tube diameter comes up a lot and somehow it never gets explained completely. I did a couple of videos that touched on this, I think, but I maybe I should do one focusing on what you get with a larger tube when I get my whiteboard back.

    In a nutshell, a larger tube give you the real estate to combine wide FOV, large adjustment range and large zoom ratio.

    One of the reasons AMG get good FOV with a 30mm tube is that it is a 4x erector, vs 6x erector on Gen 2. There are some other consideration potentially in play, like DOF, etc. For example, with the March-FX or Nightforce NX8, they are getting wide zoom ration, decent FOV and a lot of adjustment in a 30mm tube by using a very short objective lens system which makes parallax touchier and depth of field more shallow.

    I think I touched on this subject in this video:

    ILya
    Thank you Ilya,I enjoy listening to someone who knows what he is talking about.
     

    Mike_Pancake

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    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
     

    just browsing

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    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

    Lol you are literally talking to THE optics guy on the forum.

    Now you on the other hand... you I could see being the one to read ARFcom and come here claiming to know wtf you’re talking about.

    People like you don’t last long ‘round these here parts, that much I know.
     

    JakeM

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    Hahaha please enlighten me on why you disagree?
    There is a tube inside of a tube, just because the outer tube is bigger does not mean that the inner tube is bigger.
    The outer tube is made bigger, there is more room for adjustments, the inner tube is not made bigger= not any more light transmission.
    A lot of big tubed optics have big objectives, and people mistake the better light transmission because of the tube.
    Image result for pics of swarovski x5i
     

    Mike_Pancake

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    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
     

    Mike_Pancake

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    There is a tube inside of a tube, just because the outer tube is bigger does not mean that the inner tube is bigger.
    The outer tube is made bigger, there is more room for adjustments, the inner tube is not made bigger= not any more light transmission.
    A lot of big tubed optics have big objectives, and people mistake the better light transmission because of the tube.
    Image result for pics of swarovski x5i
    If the objective lense is bigger it will take in more light... a larger tube mean more light will pass through also.

    Its the same principle with cameras... bigger the lense and aperture, the brighter a picture will be... its simple...

    Now i will agree that if the inner tube is small then light would not be passed through regardless the objective lense... but not all inner tubes are the same size.
     

    Glassaholic

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    The best explanation I have seen on the scope tube question was answered by a gentleman on the Swarovski website and while he focusses on the difference between 1" and 30mm, the same applies between 30 and 34mm.


    Tube Size Matters – But Not Much
    Brightness is a product of exit pupil (EP) diameter and anti-reflection coatings. The EP is the little circle of light seen in an eyepiece held about 18 inches from your eye and aimed at a bright wall or sky. Its diameter is determined by the objective lens diameter divided by the scope's magnification. Thus, a 50mm objective at 10X would yield a 5mm EP. At 6X the EP would enlarge to 8.3mm and at 4X it would be 12.4mm. At 50mm objective at 25 power would produce a tiny 2mm EP. These numbers are the same whether the main tube is 30mm or 26mm (1-inch.)
    A scope's EP corresponds to your own pupil, which dilates from about 2mm in bright sunlight to perhaps 7mm in the dark. If your scope's exit pupil is smaller than your pupil, it can't transmit all the light you can use. If it's larger, the extra rim of light bounces off your iris and never enters your pupil to stimulate your retina. Wasted light. But an excess diameter of exit pupil does give your eye more room to wander around in without showing edge blackout, so that's something.
    The reason a 30mm main tube scope isn't inherently brighter than a 1-inch scope is because both carry internal lenses much larger than 7mm, so there is no loss of light through either. The reason some 30mm scopes appear to project brighter views is probably because they were built with the absolute finest materials and effective light transmission (how much light the scope passes through) determines brightness, is a product of the number of air-to-glass surfaces in the scope (the fewer the better) and the anti-reflection coatings on those lenses. (The more the better.)
    So what, then, are the advantages of a 30mm scope tube? The walls can be made thicker for added strength and durability or the internal lenses can be made slightly larger, which increases optical performance simply because larger lenses always perform better than smaller ones, all else being equal. Alternatively, manufacturers can keep internal lenses the same size as those in their 1-inch scopes and use the extra internal room for long range reticle adjustments.
     
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    Glassaholic

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    Scope tube diameter comes up a lot and somehow it never gets explained completely. I did a couple of videos that touched on this, I think, but I maybe I should do one focusing on what you get with a larger tube when I get my whiteboard back.

    In a nutshell, a larger tube give you the real estate to combine wide FOV, large adjustment range and large zoom ratio.

    One of the reasons AMG get good FOV with a 30mm tube is that it is a 4x erector, vs 6x erector on Gen 2. There are some other consideration potentially in play, like DOF, etc. For example, with the March-FX or Nightforce NX8, they are getting wide zoom ration, decent FOV and a lot of adjustment in a 30mm tube by using a very short objective lens system which makes parallax touchier and depth of field more shallow.

    I think I touched on this subject in this video:

    ILya
    I think the bigger question here is who took ILya's whiteboard? :mad: :LOL:
     

    koshkin

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    If the objective lense is bigger it will take in more light... a larger tube mean more light will pass through also.

    Its the same principle with cameras... bigger the lense and aperture, the brighter a picture will be... its simple...

    Now i will agree that if the inner tube is small then light would not be passed through regardless the objective lense... but not all inner tubes are the same size.


    In a photographic lens the amount of light that gets through is constrained by the limiting aperture. Same for a riflescope. Except tube diameter does not define the limiting aperture. At higher magnifications, it is the objective diameter.

    Now, if you are interested in optics or how simple optical systems work, go take a class or read a book. I can make some recommendations. It is not very complicated.

    ILya
     
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    JakeM

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    If the objective lense is bigger it will take in more light... a larger tube mean more light will pass through also.

    Its the same principle with cameras... bigger the lense and aperture, the brighter a picture will be... its simple...

    Now i will agree that if the inner tube is small then light would not be passed through regardless the objective lense... but not all inner tubes are the same size.
    Post 31 is what I was saying.
     

    JakeM

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    If the objective lense is bigger it will take in more light... a larger tube mean more light will pass through also.

    Its the same principle with cameras... bigger the lense and aperture, the brighter a picture will be... its simple...

    Now i will agree that if the inner tube is small then light would not be passed through regardless the objective lense... but not all inner tubes are the same size.
    Not all inner tubes are going to be the same, but they will be close enough not to matter that much.
     

    Glassaholic

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    If the objective lense is bigger it will take in more light...

    This is correct, the front objective takes in the light, but watch ILya's video and you'll see how light is then directed through the tube.

    a larger tube mean more light will pass through also.
    This is incorrect, see the quote from the Swarovski forum I posted above, how much light that actually passes through the tube is not necessarily determined by the tube size, it is an optical principal based on the exit pupil and how wide our own eye's pupil can dilate. Can a 150mm objective gather more light than a 56mm objective, yes, but what's the point when the exit pupil is waaaay above what our eye can take in (as Ron mentions in the Swarovski post, it is "wasted light" in essence; however, it can have an effect on eyebox which allows for more forgiveness when it comes to eye position), and the same goes with the tube, even the smallest we have today (a 1" (25.4mm) outer tube diameter) still has glass larger than the required 7mm for light to pass through. Here is the last paragraph from the article above:

    The reason a 30mm main tube scope isn't inherently brighter than a 1-inch scope is because both carry internal lenses much larger than 7mm, so there is no loss of light through either. The reason some 30mm scopes appear to project brighter views is probably because they were built with the absolute finest materials and effective light transmission (how much light the scope passes through) determines brightness, is a product of the number of air-to-glass surfaces in the scope (the fewer the better) and the anti-reflection coatings on those lenses. (The more the better.)

    During the day a 56mm objective scope pulls in a lot more light than our eye needs; however, we don't buy 56mm scopes for solely daytime use, there are other benefits to the larger objective, especially when it comes to low light situations.

    Its the same principle with cameras... bigger the lense and aperture, the brighter a picture will be... its simple...
    A camera lens is designed to direct light to a sensor whereas a rifle scope is designed to direct light to your eye, most camera sensors are far bigger than what our eye requires hence the need for larger diameter objectives, but again it's not the barrel of the lens that determines how much light hits that sensor rather it is the front objective.

    One final thought, the human eye is a very poor comparative detector to brightness change because of our brains ability to communicate what our eye actually picks up, this is why I always recommend to perform scope tests in poor lighting condition (after the sun goes down), this is when our eyes are at their worst and it allows us to identify flaws within a scopes design much more easily than during the day - I have seen many scopes perform very well during normal daytime conditions and fall apart when the light gets low.

    PS - I am not an optical engineer so understand this information is what I've gleaned in my passion for long range shooting over the years but I am prone to error at times and always willing to be corrected.
     
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    Cartman

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    Pancake, maybe you could post your bio highlighting your expertise in this field. Along with some technical proof of your concept. With Ilya's permission I'll post his as copied from his website.
     
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    notorious

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    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

    You just told Koshkin, a guy that has forgotten more about scopes than you will ever know, that he doesn't know what he's talking about.

    I've seen it all. ?
     

    lash

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    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
    There is a saying that goes, “you don’t know what you don’t know.” In essence, if you think that you already know it all and don’t pay attention to multiple clues that maybe there’s something that you’re missing, you will never learn what it is that you don’t really know. Because you already think you know it all.

    Now, if you can get off your indignant stance and take some time to actually learn the nuances that explain why your assumption is wrong, you’ll be ahead of the game and smarter for it. There are people here that are more than willing to help people learn everything that they can. The trick is that you have to be willing to learn.

    You don’t know what you don’t know. ;):cool:
     

    ChrisAU

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    Scope tube diameter comes up a lot and somehow it never gets explained completely. I did a couple of videos that touched on this, I think, but I maybe I should do one focusing on what you get with a larger tube when I get my whiteboard back.

    In a nutshell, a larger tube give you the real estate to combine wide FOV, large adjustment range and large zoom ratio.

    One of the reasons AMG get good FOV with a 30mm tube is that it is a 4x erector, vs 6x erector on Gen 2. There are some other consideration potentially in play, like DOF, etc. For example, with the March-FX or Nightforce NX8, they are getting wide zoom ration, decent FOV and a lot of adjustment in a 30mm tube by using a very short objective lens system which makes parallax touchier and depth of field more shallow.

    I think I touched on this subject in this video:

    ILya

    @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?
     

    lash

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    No doubt WJM, but when entering a room of strangers you would like to get to know a softer approach isn't a bad idea. :)
    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.
     

    Cartman

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    Pancake, here is some background on Ilya Koshkin:

    "I hold a B.S. in Applied Physics from CalTech and an MBA from University of California in Los Angeles (UCLA)

    I have spent most of my professional career working on projects related to test and measurement as well as image and data analysis. I started out working in telecommunications with fiber and micro optics. In 2002, I transitioned into infrared imaging and worked on imaging sensors for land-based astronomy, sattelite surveillance and night vision weapon sights for both Rockwell Scientific and Raytheon. Since then, I have spent some time involved with CMOS imaging sensors for high end digital photography, cinema and video conferencing. More recently, I transitioned back into the defense/aerospace world and I work with all manner of electro-optical test instrumentation."

    I believe someone also quoted an optical engineer from Swaro up above.

    I'm sure I'm not alone in wondering what credentials and technical explanations you have that demonstrate you know more about the physics of light than is taught at CalTech and what Swaro knows about it. So please, regale us with your credentials etc. I have learned a lot reading over the years. And I'm prepared to learn something new today as well. Thanks in advance.