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Rifles, Reloading, Optics, Equipment
Long Range Scopes and Other Optics
Accuracy of ParallexMarks on SF or AO
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<blockquote data-quote="Bart B" data-source="post: 99155" data-attributes="member: 5302"><p>I wish everyone in the world who uses rifle scopes would learn and understand that you do not adjust parallax. And those marks on the thing that changes the range the rifle scope is focused at are usually marked in yards or feet or meters. And those marks don't mean parallax; they mean distance or range the scope's front lens is focused at. </p><p></p><p>The only time parallax exists is when the aiming eye is off center from the rifle scope's optical axis "AND" the scope is focused at some distance other than what the target is. How much parallax there is or how much you notice it depends on how far the aiming eye is off the scope's axis and how far in front or behind the reticule the target image's focus is. In other words, if the aiming eye is positioned on the scope's axis parallax will never exist regardless of the difference between focus and target distance or range.</p><p></p><p>Regarding errors in marking the focus adjustment, consider the following facts. When a batch of lenses are made, each one does not have exactly the same curved surfaces. Which means they do not all have the same focal length. As there's usually two or three individual lens elements cemented together at the front of the scope that comprise the objective lens assembly. And each objective lens assembly for a given scope make and model will therefore not have exactly the same focal length; they'll vary a few tenths of a millimeter or more. As each objective lens assembly is mounted in a lens barrel that's made to the same mechanical specs for a given scope make and model, it will move the same amount front and back for a given amount of focus change that moves the barrel back and forth.</p><p></p><p>All of which means that if the focusing mechanics move the objective lens .0010 millimeter when changing focus from 400 to 500 yards but the actual focal length of the objective lens requires it to move only .0009 millimeter then obviously there's an error. How much will this change things? Nobody will ever notice it.</p><p></p><p>If you want to see how critical focusing is for a 150 mm lens (typical of most high magnification rifle scopes' objective lens) at 500 yards, look at a camera lens of that same focal length, then notice how far you have to move it to change focus from 400 to 500 yards. The finest camera lenses in the world are not exactly the same, but the mounts they are put it sure are.</p></blockquote><p></p>
[QUOTE="Bart B, post: 99155, member: 5302"] I wish everyone in the world who uses rifle scopes would learn and understand that you do not adjust parallax. And those marks on the thing that changes the range the rifle scope is focused at are usually marked in yards or feet or meters. And those marks don't mean parallax; they mean distance or range the scope's front lens is focused at. The only time parallax exists is when the aiming eye is off center from the rifle scope's optical axis "AND" the scope is focused at some distance other than what the target is. How much parallax there is or how much you notice it depends on how far the aiming eye is off the scope's axis and how far in front or behind the reticule the target image's focus is. In other words, if the aiming eye is positioned on the scope's axis parallax will never exist regardless of the difference between focus and target distance or range. Regarding errors in marking the focus adjustment, consider the following facts. When a batch of lenses are made, each one does not have exactly the same curved surfaces. Which means they do not all have the same focal length. As there's usually two or three individual lens elements cemented together at the front of the scope that comprise the objective lens assembly. And each objective lens assembly for a given scope make and model will therefore not have exactly the same focal length; they'll vary a few tenths of a millimeter or more. As each objective lens assembly is mounted in a lens barrel that's made to the same mechanical specs for a given scope make and model, it will move the same amount front and back for a given amount of focus change that moves the barrel back and forth. All of which means that if the focusing mechanics move the objective lens .0010 millimeter when changing focus from 400 to 500 yards but the actual focal length of the objective lens requires it to move only .0009 millimeter then obviously there's an error. How much will this change things? Nobody will ever notice it. If you want to see how critical focusing is for a 150 mm lens (typical of most high magnification rifle scopes' objective lens) at 500 yards, look at a camera lens of that same focal length, then notice how far you have to move it to change focus from 400 to 500 yards. The finest camera lenses in the world are not exactly the same, but the mounts they are put it sure are. [/QUOTE]
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Rifles, Reloading, Optics, Equipment
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