Scope questions

[Mike D]

Do you have equations , calculations, or tables when the tube is 30mm?



Sincerely interested. Thanks.

No difference. Your exit pupil will always be smaller than 30mm.

Larger main tubes offer more elevation and windage adjustments and when getting into 6x and 8x adjustment scopes they need the extra diameter to allow that much range of adjustment for the lenses to shift.




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[150class]

As said before the glass, multi coatings, and bell size. Exit pupil is how to calculate it and also some scopes gather more light then our pupils can absorb or transfer so there's limitations on our end.

[Swampa]

Mike D knows the specifics. All I can say is words like Swarovski, Zeiss, Leica help that equation as well


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[TexMax]

No difference. Your exit pupil will always be smaller than 30mm.

Larger main tubes offer more elevation and windage adjustments and when getting into 6x and 8x adjustment scopes they need the extra diameter to allow that much range of adjustment for the lenses to shift.




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For now. I'm sure someone has a 1-whatever by large objective in the works. But it wouldn't be relative to what the eye could see anyway lol.

What mike (and others) are saying is right. Tube diameter is irrelevant to light transmission. Assuming you are not severely limiting yourself on exit pupil with the formula provided above it is really easy to see how the quality of your glass plays an equal if not more significant role than objective size. Your running the image through multiple sets of lenses all with the ability to distort the image or kill light. A 40mm zeiss and many other quality scopes will kick the pants off a low end 50mm all day.

[tigerscowboy]

For now. I'm sure someone has a 1-whatever by large objective in the works. But it wouldn't be relative to what the eye could see anyway lol.

What mike (and others) are saying is right. Tube diameter is irrelevant to light transmission. Assuming you are not severely limiting yourself on exit pupil with the formula provided above it is really easy to see how the quality of your glass plays an equal if not more significant role than objective size. Your running the image through multiple sets of lenses all with the ability to distort the image or kill light. A 40mm zeiss and many other quality scopes will kick the pants off a low end 50mm all day.

In your honest opinion, where would that actually rate something like a Vortex Viper 4-16 x 50 w/30mm tube? I've read all that is out there, and then put it all to the eye test. Appreciate your input here. Thanks.

[Old Bald Guy]

The pupil of the average human will expand to approx. 7 mm in extremely low light situations so magnification x 7 gives you the optimum objective lens diameter [6x42][8x56] etc. Lens quality, coatings, design and construction make a tremendous difference in low light performance.
Until you have used a 8x56 Kahles @ 350yds across a oat patch 29 minutes after sunset-or way longer if it's pigs- you probably won't understand.

[tpcollins]

Glass, coatings and exit pupil all play a part in the amount of light that gets to your eye and the quality of the image that goes with it.

Exit pupil is strictly a mathematical formula of the objective diameter divided by the magnification. For example 40mm objective divided by 10x magnification would = a 4mm exit pupil. You want to stay at 4mm minimum, but higher doesn't necessarily mean better; 4mm is ideal.

Glass quality and coatings is where you get what you pay for.


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The usable exit pupil can depend on a persons age. As we get older we lose the ability for our pupil to expand. When younger we might be able to use 6-7mm whereas when we get into our 60's it might be tough to take advantage of much more than 5mm.

At one time I had Zeiss Victory 8x42 binocular with a 5.25mm exit pupil and then I bought the Zeiss Victory 8x32 binocular with a 4mm exit pupil. I did a side by side comparison one morning looking across a picked bean field and the brightness of the 8x42 was clearly noticeable.

That 3-9x40mm scope for example has an exit pupil of a bit over 13mm on 3x and just over 4mm at 9x. If you looked thru that 3-9 scope at 9x in low light and started turning the magnification down, I would think you wouldn't notice any additional brightness after getting past 6x or so.

And the most logical way to improve on a specific exit pupil value is with quality glass (flourite) and coatings that transmit light and that cost money.

[Mike D]

Typically the human pupil is around 4mm at dusk/dawn. No matter how much more light you transmit to the eye through the exit pupil of any optic, that's all your eye will physically absorb and any additional can cause your pupil to constrict.

If I recall in total darkness the human eye dilates to about 7mm.


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[tigerscowboy]

Thanks Mike. High interest and learning with this thread.

[LFD2037]

I have a 50mm obj. w/34mm tube scope. It works well in low light.

[Gary Roberson]

Have you looked at Trijicon???? I am shooting the 3-9x40's on my rifles and love them for brightness and accuracy of adjustments.
Adios,
gary