Hi oldelkhunter,

I have never owned either of the Kahles you've asked about....but I have owned their 1.5X6 power. I do not recall the size of the objective lens but it had a 30mm tube. I do remember the objective wasn't really large...and that scope passed all the light a human eye can distinguish. You reach a point of diminishing return on objective size. (And when the exit pupil diameter exceeds the ability of the human eye to distinguish the existing light....it doesn't make any more difference as measured by a human eye.)

Remember not only will that be affected by the size of the objective lens...but by what power your scope is set at as well. You can turn down the power to increase exit pupil diameter on a scope. But many other factors will play an important role as well. Good lenses will transmit more light than poor lenses. The coating on the lenses will have an affect on light transmission. And if "all other factors are equal".....a 30mm tube will pass light more efficiently than a 1" tube.

For more information concerning exit pupil and light transmission go to:

http://web.ask.com/redir?bpg=http%3a....htm&qte=0&o=0

Then scroll down to:

Understanding Exit Pupil Detail Resolution

To See The Light
Light Gathering vs Light Transmission
Relative Brightness vs Twilight Factor


There are only a handful of short paragraphs of information, (don't be intimidated by the URL). It is easily understood and concise. And though it is written regarding binoculars....exactly the same information applies to scopes.

Hope it helps!