And this is from Nikon:

"Question

Do the 30mm[/b] scope tubes have oversized optics, or are they just 1 inch tube optics placed in a 30mm[/b] tube?


Answer

The 30mm[/b] scopes are actual 30mm[/b] scopes with optics that are larger than the standard 1” scopes. This does not gather or transmit any more light than a 1” scope, but it does provide a larger sweet spot to enhance resolution."


So, resolution may be enhanced, but again, brightness is not affected.