March 31st, 2017

How Scopes Work — Understanding Lenses and Light Paths

Accurateshooter.com optics rifle scope Swarovski

The Swarovski Optik website features a blog with interesting technical articles. In the “On Target” series of blog stories, Swarovski has provided a handy explanation of how optics systems work, with exploded diagrams of rifle scopes, spotting scopes, and binoculars. CLICK HERE for Swarovski Optics Blog.

Accurateshooter.com optics rifle scope Swarovski

Scope Terminology
Focusing Lens
The focusing lens is an adjustable lens inside the optical system for focusing the image at different distances…. In the case of rifle scopes, apart from focusing, the focusing lens also facilitates parallax compensation.

Diopter Adjustment
For rifle scopes, the reticle can be focused using the diopter adjustment on the eyepiece, thereby correcting any visual impairment. [Editor’s Note: Movable eyepiece diopter adjustment is not offered on all rifle scopes. It is a useful feature on Swarovski and other premium scopes. This allows shooters who need eyeglasses to get a sharply focus image even without wearing corrective lenses. Of course shooters should always wear ANSI-certified eye protection. With the diopter, folks who need correction can use inexpensive, non-Rx safety eyewear instead of expensive prescription safety glasses.]

Reversal System
The purpose of the reversal system is to reverse the image by means of prisms in binoculars and telescopes, and lenses in rifle scopes….The lens reversal system is needed in rifle scopes to control the variable magnification and move the exit pupil[.]

Parallax Explained
What is Parallax? What problems can Parallax create when you are shooting? Many novice shooters can’t answer those questions easily. Likewise, many folks don’t understand how to use their front or side-focus parallax controls most effectively. Yes the parallax control basically sharpen focus at different target distances — but there’s more involved. This video offers helpful insights.

Resource tip by EdLongRange. We welcome reader submissions.

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