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?