In theory this is true, but glass and coating quality plays a big part in perceived brightness.
Not all 8X42’s or 3-9X40’s are equal on light transmission.
Originally Posted by UncleAlps
Many have recommended 6x scopes with at least 30 mm objective lenses as the solution to low light. This combination provides a 5mm exit pupil which is widely accepted as the required amount of light to work with the human eye. The rule of 5x works with any variable scope just as well as a fixed power scope. A 3x9-32mm scope set at 6x also provides the same 5mm exit pupil. The old 3x9 -40 works as well up to 8x and costs much less than the fixed 6x scopes. 3x9's are the bread and butter of each major scope manufacturer. The lower price and similar quality makes them the best buy.
But don't listen to me. Get yourself a 10x fixed power with a 50mm objective so you have more confidence to shoot at shadows in the woods 30 minutes after sunset. Just don't shoot your buddies by accident.
