A Leupold Vari-X III 6.5 - 20x scope with focusing ocular bell and focusing objective bell (Parallax adjustment).


The Parallax adjustment.

Parallax - A condition, when looking through a telescopic sight, when a movement of the eye, up, down or sideways, changes the position of the reticle with respect to the target. This condition is caused by the reticle not being in proper focus with the objective lens. It is difficult to achieve reliable accuracy while there is a parallax problem. And, the higher the magnification, the more likely parallax will be an issue. The cure is to focus the scope for the range it is to be used. Most scopes may be focused by rotating the ocular bell. Many high-powered scopes have a parallax adjustment---the ability to focus via the objective bell.

Also: by its more general definition, the angle described by two different points of view converging on an object---such as the view through a rangefinder camera's viewfinder (the top lens in the Rolliflex camera below) in relation to the view through the main lens (the bottom lens, below)---barely noticable at long distance, but rather inconvenient at very close ranges; the view as seen through a telescopic sight in relation to the line of the bore.




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