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Extreme Long Range Hunting & Shooting (ELR)
Why are more expensive scopes so much brighter at high power?
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<blockquote data-quote="Hugnot" data-source="post: 2902798" data-attributes="member: 115658"><p>Optical science guys use the term - "numerical aperture" or NA to describe a lens. A lens with a bigger NA has a bigger angle of acceptance, like a cone with a larger diameter as related to cone height or length. This results in more light being gathered in the pointy end of the cone providing better resolution.</p><p></p><p>Higher priced scopes have better coatings that reduce light reflection (light bouncing off lens surface) and almost always have larger objective lenses and use higher quality glass. The result is superior resolution when cranked up to max powers.</p><p></p><p>Thru decades of peering thru various optics I think (opinion of one who struggled thru Physics 201 & 202):</p><p></p><p>Glass quality & coatings matter. Some 40 mm objective lens scopes are noticeably brighter than other 50mm objective lens scopes - both set at the same power.</p><p></p><p>Scopes with fat tubes like 30mm & 34mm will have internal lenses having larger NA's.</p><p></p><p>My Vortex Viper 20-60X85 spotter shows accelerated signs of distress (dull fuzzies) at about 45X magnification, at that point the diameter of the light beam (aperture) going into my eye pupil is reduced resulting in increased light diffraction (light spreading) & image degradation.</p><p></p><p>Given a choice of scope that would fit into almost all of my shooting - a 16X50 with 30 mm tube, highest quality coating & glass. Probably side focus. Mil Rad reticle & adjust. No reliance on springs for scope adjustments.</p><p></p><p>I got 3 Sightron STAC 3-16X42's that work just fine for almost every occasion - on sale at Midway for $250 - what a deal! Long range rodent shooting is better with the 4-20X50 Sighton STAC scopes.</p></blockquote><p></p>
[QUOTE="Hugnot, post: 2902798, member: 115658"] Optical science guys use the term - "numerical aperture" or NA to describe a lens. A lens with a bigger NA has a bigger angle of acceptance, like a cone with a larger diameter as related to cone height or length. This results in more light being gathered in the pointy end of the cone providing better resolution. Higher priced scopes have better coatings that reduce light reflection (light bouncing off lens surface) and almost always have larger objective lenses and use higher quality glass. The result is superior resolution when cranked up to max powers. Thru decades of peering thru various optics I think (opinion of one who struggled thru Physics 201 & 202): Glass quality & coatings matter. Some 40 mm objective lens scopes are noticeably brighter than other 50mm objective lens scopes - both set at the same power. Scopes with fat tubes like 30mm & 34mm will have internal lenses having larger NA's. My Vortex Viper 20-60X85 spotter shows accelerated signs of distress (dull fuzzies) at about 45X magnification, at that point the diameter of the light beam (aperture) going into my eye pupil is reduced resulting in increased light diffraction (light spreading) & image degradation. Given a choice of scope that would fit into almost all of my shooting - a 16X50 with 30 mm tube, highest quality coating & glass. Probably side focus. Mil Rad reticle & adjust. No reliance on springs for scope adjustments. I got 3 Sightron STAC 3-16X42's that work just fine for almost every occasion - on sale at Midway for $250 - what a deal! Long range rodent shooting is better with the 4-20X50 Sighton STAC scopes. [/QUOTE]
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Why are more expensive scopes so much brighter at high power?
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