Originally Posted By: knockemdownThe limiting factor of the amount of useable light a scope transmits to your eye has been & always will be EXIT PUPIL.
Objective diameter (in mm) divided by magnification power = exit pupil (in mm) Depending on YOUR eyes, how much light YOU can process is somewhere between 4-9mm, with a good average being 6-7mm.
Consider this. YOUR pupil can dilate (open) up to 6mm. That is the maximum amount of light your eye can process.
So then, if you want to compare scopes, do the math beforehand & set the mag ring on each so that the exit pupil value is equal. THEN, you can begin to compare glass quality, coatings...yada yada
To YOUR 6mm dilated eyes, the baby NXS 2.5-10x24 is has the same 6mm exit pupil on 4X as the full size NXS 3-15x56 does on 9.3X. (56/6 = 9.3)
Sooo, thanks to the larger objective of the full sized NXS, you can ideally use MORE of that scope's magnification range for low/no light shooting.
Now consider a NXS 5.5-22x50. You will only be able to get to 8.3X before you notice it becoming 'dimmer' than the 3-15x56 on 9.3x power. (50/6 = 8.3)
Comprehende?
So, of the three just I described, the most useable scope for low/no light shooting is obviously the 3-15x56. A good bit of the magnification range of that particular scope will net you a bright view, thanks to that >6mm exit pupil from 3x up to 9.3X magnification.
The 'baby' NXS is will only look 'bright' from 2.5x-4X power. Above that magnification, the sight picture will get progressive dimmer as you crank up the mag ring.
Same for the 5.5-22x50. Based on your "ideal" 6mm exit pupil, that scope's 'brightest' range is between 5.5x-8.3X magnification.
So in the end, it's up to the shooter to define what performance he's wanting from his optic. Then, choose the model wisely.
Anyone who makes a 'blanket statement the "XXX" brand gathers more light than "YYY" brand doesn't have a friggin' clue what they are talkin' about...
Geez there, knockemdown!
Did I say something to make you mad??