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35mm vs 1" tube

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Unread 09-21-2011, 03:17 PM
Junior Member
Join Date: Oct 2009
Posts: 26
35mm vs 1" tube

I am looking to pick up a new scope and fad now seems to be 35mm tubes. I hear people saw all the time that the 35mm tube is supposed to bring in more light and make it better in low light conditions and make the scope clearer. However, I was talking with an older guy in a gun store about that and he seemed to debunk the whole "more light" theory. Here's his point.

The human eye will dilate to approx. 5mm in low light conditions. I know this to be true from my medical background. Now exiting the back of the scope is a shaft of light. That shaft of light can be calculated by the size of the objective divided by the power of the scope. Which means, a 50mm objective at 10 power will have a shaft of light that is 5mm in diameter and will work great in low light. However, if you crank that same scope up to 20 power the shaft of light exiting the scope will be 2.5mm and your eye will be starving for light which will make the scope seem dim and grainy. None of this has anything to do with the size of the tube the light is going through.

He said the only advantage the larger tube would offer would be more travel in your adjustment knobs since there is physically more room inside the scope. But even then, he said that a lot of scope manufactures place 1" mechanisms in a 35mm tube and ship it out the door and charge a higher price for it.

What are your thoughts on this? Does a 35mm tube really make a brighter scope or does it have more to do with the quality of glass used and making sure your power set too high?
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Unread 09-21-2011, 04:35 PM
Platinum Member
Join Date: Jan 2004
Location: Blackfoot, Idaho
Posts: 8,876
Re: 35mm vs 1" tube

Does a 35mm tube really make a brighter scope?

NO!! The larger tube allows more vertical and horizontal reticle movement.

Brighter has to do with quality of lens material, polishing methods and coatings.
I may be the slowest guy on the mountain . . . . but . . . . I'm on the mountain!
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Unread 09-22-2011, 08:05 AM
Silver Member
Join Date: Feb 2002
Location: Nebraska
Posts: 410
Re: 35mm vs 1" tube

More light with the larger tube? NO. Roy and the guy in the gun shop pretty much said it all. Your not going to get more light with a larger tube no matter what you do but you do get a lot more adjustment with it.
Up to a point the larger objective lens will give you more light up to a point. You were given pretty accurate advice. What does it best are the lens coatings and lenses.
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Unread 09-22-2011, 08:31 AM
Junior Member
Join Date: Oct 2009
Posts: 26
Re: 35mm vs 1" tube

Thanks guys, That's what I thought. I am looking and getting a new scope and didn't want to spend the extra $ if I didn't have to.
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