Gather or transmit more light to your eye

Discussion in 'Optics' started by TXCOONDOG, Jul 9, 2013.

  1. TXCOONDOG

    TXCOONDOG Highlands, Texas

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    Some information that is good to know:


    A 50mm objective does not gather or transmit more light to your eye than a 40/42mm objective in a 1" tube. It is the the exit pupil and the light transmission quality of the glass that determines low light visibility and what you can see at sunrise, sunset, and at night. The exit pupil should be as large as the human eye under the same conditions. The exit pupil is calculated by dividing the objective diameter by the power setting on the scope. At night a 42mm objective scope set on 6 power will give you a 7mm exit pupil which is optimal and matches your eye and transmits the maximum light the eye can see.


    From Nikon: "As far as 30mm vs. 1", they do not gather or transmit any more light than a 1" scope, but they provide a larger sweet spot to enhance resolution."


    From Leupold: "The key to a scope providing a bright image to the shooter is not how much light it "gathers" but how much usable light it transmits. "Gathers, transmits, what's the difference?" Quite a lot, actually. First of all, rifle scope do not "gather" light, they transmit it. Yes, large objective scopes allow more light to enter the scope, but that by itself does not guarantee that the image will be any brighter than a smaller objective scope's. In other words, the better the glass and coatings you get, the better your night hunting."


    Since a healthy eye pupil is 7, think in numbers of 7:


    First number represents magnification setting, 7 represents healthy exit pupil, last number is your objective lens size.


    1X7= 7MM
    2X7= 14MM
    3X7= 21MM
    4X7=28MM
    5X7=35MM
    6X7=42MM
    7X7=49MM
    7X8=56MM
     
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  2. Ratdog68

    Ratdog68 LSB Official Story Teller LoneStarBoars Supporter

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    We have stickage... we have stickage folks. Good find.
     
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  3. rob072770

    rob072770 Lewisville NC SUS VENATOR CLUB LoneStarBoars Supporter

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    I love to learn new stuff
     
  4. pruhdlr

    pruhdlr Cantonment,Fla. SUS VENATOR CLUB

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    I have been using the basic formula for some years now. The way that I heard it is the younger eyes will dilate down to 5mm,for us ol' farts use the 7mm formula. I used this while night hunting coyotes in Maine. The typical was to drag a road kill deer out onto a frozen lake with my snowmobile,then build a snow shelter on the bank and hunt the full moon,clear nights. I would actually crank back the power setting as the ambient light faded. I do the same thing night hunting in Fla.

    I will say though, that a 30mm will give you more field of view and allow you to track a moving target somewhat better. --- pruhdlr
     
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  5. PRyan1877

    PRyan1877 Roselle, Illinois LoneStarBoars Supporter

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    This is good useful information. Thank you for sharing it with us.
     
  6. BigRedDog

    BigRedDog LSB Active Member SUS VENATOR CLUB Vendor LoneStarBoars Supporter

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    Not sure that I follow the reasoning.

    Don't know that I agree.
     
  7. Brian Shaffer

    Brian Shaffer Pro Staff Third Coast Thermal SUS VENATOR CLUB LoneStarBoars Supporter

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    I am rather disappointed in the Leupold statement, or rather, misstatement. TCD is right in that a scope neither gathers or transmits.
     
  8. DaveABQ

    DaveABQ Albuquerque, NM

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    Brian Shaffer likes this.
  9. Drift

    Drift LSB Member

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    Pruhdir is right in that older eyes don't see in the dark as well as younger eyes. Where he is mistaken is that older eyes do not dilate as much as younger eyes. So 5 mm is about all the light older eyes let in; so any light> about 5 mm is wasted.
     
  10. rob072770

    rob072770 Lewisville NC SUS VENATOR CLUB LoneStarBoars Supporter

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    Well,that explains a lot and my eye Doc told me that cataracts have started. Typical for my young age Ha Ha.
     

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