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Rifles, Reloading, Optics, Equipment
Long Range Scopes and Other Optics
Question about exit pupil for scopes with really high magnification.
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<blockquote data-quote="bruce_ventura" data-source="post: 1041785" data-attributes="member: 34084"><p>Four things to keep in mind: </p><p></p><p>1. The resolution of the adult human eye is about 1 MOA (20/20 vision). Objects smaller than this size are just blur. Younger people can have a little better resolution, say about 0.7 MOA. </p><p></p><p>2. The resolution of a really good telescope is loosely called the "diffraction limit". For a 56 mm objective telescope the resolution is about 27 times better than the adult eye, or about 39 times better than a young, exceptional eye. </p><p></p><p>So, above a magnification of roughly 33X, give or take, a 56 mm objective telescope is magnifying blur, but it's not providing any more detail about the target to someone with good vision. Below that magnification, the eye is the limiting factor. </p><p></p><p>If you have vision problems that cannot be improved with correction, then additional magnification can be helpful. For example, an adult with 20/40 vision with correction would benefit from a 54X telescope. </p><p></p><p>3. Brightness in daytime decreases dramatically above 33X for most people. At a magnification of 54X, the image through a 56 mm objective telescope is roughly 1/4th the brightness perceived by the naked aye. At 80X, the brightness is about 1/9th that of the naked eye. </p><p></p><p>4. Glare due to "stray light" increases dramatically with magnification in rifle scopes. For example, glare is more noticeable at 20X than at 10X. Even for a good (low glare) rifle scope, stray light rays are concentrated just outside the exit pupil. When the exit pupil is smaller than the eye pupil or the eye is not properly aligned with the exit pupil, this stray light gets into the eye pupil and washes out the image. </p><p></p><p>So, unless you have vision problems, magnification above about 33X for a 56 mm objective rifle scope is not beneficial, and usually degrades the image rather than enhancing it. </p><p></p><p>However, we live in a society where bigger is better regardless of physics, and marketing people exploit that fact.</p></blockquote><p></p>
[QUOTE="bruce_ventura, post: 1041785, member: 34084"] Four things to keep in mind: 1. The resolution of the adult human eye is about 1 MOA (20/20 vision). Objects smaller than this size are just blur. Younger people can have a little better resolution, say about 0.7 MOA. 2. The resolution of a really good telescope is loosely called the "diffraction limit". For a 56 mm objective telescope the resolution is about 27 times better than the adult eye, or about 39 times better than a young, exceptional eye. So, above a magnification of roughly 33X, give or take, a 56 mm objective telescope is magnifying blur, but it's not providing any more detail about the target to someone with good vision. Below that magnification, the eye is the limiting factor. If you have vision problems that cannot be improved with correction, then additional magnification can be helpful. For example, an adult with 20/40 vision with correction would benefit from a 54X telescope. 3. Brightness in daytime decreases dramatically above 33X for most people. At a magnification of 54X, the image through a 56 mm objective telescope is roughly 1/4th the brightness perceived by the naked aye. At 80X, the brightness is about 1/9th that of the naked eye. 4. Glare due to "stray light" increases dramatically with magnification in rifle scopes. For example, glare is more noticeable at 20X than at 10X. Even for a good (low glare) rifle scope, stray light rays are concentrated just outside the exit pupil. When the exit pupil is smaller than the eye pupil or the eye is not properly aligned with the exit pupil, this stray light gets into the eye pupil and washes out the image. So, unless you have vision problems, magnification above about 33X for a 56 mm objective rifle scope is not beneficial, and usually degrades the image rather than enhancing it. However, we live in a society where bigger is better regardless of physics, and marketing people exploit that fact. [/QUOTE]
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Rifles, Reloading, Optics, Equipment
Long Range Scopes and Other Optics
Question about exit pupil for scopes with really high magnification.
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