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Thread: 1" vs 30mm light transmission?

  1. #1

    1" vs 30mm light transmission?

    I'm shortly going to be looking for a new scope and have narrowed the field to a handful of different options... One of these being a Swaro z3. This scope has a 1"tube, will this mean the scope will be less good at dawn/dusk than a 30mm tubes scope or will the difference be negligible?
    Last edited by palmer_mike; 09-09-2015 at 17:48.

  2. #2
    Many get mixed up between tube size and light transmission. It makes no odds. What matters FAR more is scope design (ie nr of lenses and whether fixed or variable), lens quality, whether apochromatic or non apo lenses are used, lens coating quality and ratio of objective to ocular lens. The eye benefits from the brightest image when the objective to ocular ratio is about 7. Any decent glass should perform well form between about 4.5 to 5 though. Above 7, the eye doesn't benefit from the full lens image. If you check out specifications such as light transmission, and to what extent the lens groups have been coated, that matters more than tube diameter. Basically, 30mm tube sizes are there to allow more movement for the erector tube assembly to allow greater adjustment, something that longer range target shooters benefit from as it allows better flexibility for dialled in fire solutions without the need perhaps to use an adjustable mount.

    Prime lenses (ie non zooms) will always offer better resolution and light tramsmission than zoom lenses, so a mediocre 1" fixed scope of say 6 x 42 will usually outperform a more expensive 30mm tubed zoom scope.

  3. #3
    And you couldn't get a much better answer than that!

  4. #4
    Quote Originally Posted by crimson View Post
    And you couldn't get a much better answer than that!
    It is the premise of the OP question which is curious.

    I have a Z4i and it has a 30mm tube.

    The Z4i with the 56mm objective lens should be better than most at dawn and dusk.

    Alan

  5. #5
    Quote Originally Posted by Alantoo View Post
    It is the premise of the OP question which is curious.

    I have a Z4i and it has a 30mm tube.

    The Z4i with the 56mm objective lens should be better than most at dawn and dusk.

    Alan
    oops sorry I meant z3, I'll ammend the op. It's the Z3 4-12 x 50 I'm looking at. I currently have a duralyt 3-12 x 50 on another rifle........

  6. #6
    I'm not familiar with the Z4i but the tube size won't make a difference to light gathering. The size of the objective lens will. Basically a larger objective combined with a lesser magnification is the best combination (for light gathering). The greater the twilight factor the better.

    Courtesy of Zeiss:

    The twilight factor makes it possible to compare the performance of binoculars and scopes in low -light conditions. It is calculated by first multiplying the magnification by the objective lens diameter and then finding the square root of the result. In a 7x42 binocular, the twilight factor is therefore 17.2 - the minimum for sufficient detail recognition in twilight - and an 8x56 binocular has a twilight factor of 21.2. A comparison: An 8x30 binocular, on the other hand, has a twilight factor of 15.5 and is therefore less suitable for viewing in very low light conditions.

    so perhaps the answer could have been better��

  7. #7
    There is however the proposition of a preferred esthetic to be considered here and I'd be the first to concede the larger tube can, when suitably mounted both in terms of rings and height above action/chamber, look far more 'planted' as does a Land Rover with wider than standard tyres. This being particularly noticable when a 56mm objective blossoms from a circa 1" tube.

    This properly doesn't help Palmer Mike though!


    K
    The enemy of knowledge is not ignorance, it is the illusion of knowledge.

  8. #8
    This is true - on both points, aesthetics and not helping Palmer Mike ��

    A properly proportioned 1" scope fitted to a classic hunting rifle is a thing of elegance. A lump of 30, 34 or even 35mm is very much out of place in that context. However, each to his own and I admit to owning most variants.

  9. #9
    Quote Originally Posted by crimson View Post
    This is true - on both points, aesthetics and not helping Palmer Mike ��

    A properly proportioned 1" scope fitted to a classic hunting rifle is a thing of elegance. A lump of 30, 34 or even 35mm is very much out of place in that context. However, each to his own and I admit to owning most variants.
    I should have simply said a 56mm objective looks less incongruous when coupled to a 30mm tube but I take your wider point.



    K
    The enemy of knowledge is not ignorance, it is the illusion of knowledge.

  10. #10
    Chester P is quite right the 30mm tube does not carry more light, but it isn't there for that reason.
    A greater diameter tube allows for greater elevation for those really long shots.
    Tactical scopes have been getting wider; because the range of sniper and squad support rifles have been getting longer and longer.
    So the choice is yours; lighter scope with the same light transmission (given the objective is the same dia) but limited to say 700m or a heavy scope with the same light transmission but the ability to wind up to 1000m+ without resorting to a special base (+big cost penalty usually).
    Last edited by hybridfiat; 10-09-2015 at 10:02.

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