A Look at Telescopic Scopes

In this article, we will discuss telescopic scopes; specifically looking at objective lens size comparison, scope tube size, and the concept of parallax. To start, when would and when would you not use a 50mm objective lens. From there we will consider low-light allowance and adjustability in regard to scope tube size. Wrapping up our examination of telescopic scopes, we will explain the concept of parallax.

Are bigger scopes better? If so, why doesn’t everyone use 50mm objective lens? It’s best to remember that rarely will two shooters find themselves in the exact same situation, in the exact same environment, under the exact same conditions, and having the exact same physical characteristics or limitations. For this reason, as it is with the shooter’s choice of firearm, a 50mm objective lens may or may not be beneficial to the shooter’s needs. In long range, low-light conditions are when the 50mm objective lens really begins to show its worth. In these conditions the lens provides “improved image quality in low light conditions” and the “ability to use higher magnifications longer as available light diminishes.” (Cuthbert, 2023) For those box stand, open field deer hunters, this could be extremely advantageous in bagging those late evening arrivals. However, the added cost, weight, and profile may not be worth it for those thick bush gamesmen operating in close range. 

Many people believe that scope tube size allows more light to the shooter; however, it has more to do with adjustability than the amount of light reaching the shooter. The size of the tube affects the “adjustment travel of the erector assembly” and the larger the tube, “the more elevation adjustment possible.” (Brown, 2020) It is the erector assembly that most greatly impacts light allowance and image clarity. The increased adjustment travel and size of the erector lenses has a direct impact on these two factors.

Parallax is a concept that most of us have experienced and may not have even realized. The effect is created by viewing objects that are on two different focal planes. As your perspective of the two objects change, by moving in another direction, it appears as though one of the objects is moving. In reality, both objects are still in the exact spot. You may have noticed this just walking down the sidewalk. As you walk, if you look at two objects that are separated by some distance, or on two different planes, but are in line with each other, these objects will stay in line as long as you continue to look in that direction. As soon as you change direction or move out of line with them, the objects will begin to move from their perceived position. This is the parallax effect. 

In using scopes for shooting, the parallax effect also comes into play. If you are looking at a target at 300 yards, but the scope parallax is set for 150 yards; as you move your head the reticle will appear to move from its previous position. Just as the objects in the example above moved. The objective and reticle are on two different focal planes. If the scope has a parallax adjustment, the shooter could move the reticle to align with the same plane as the target. The reticle would now remain in roughly the same position as you move your head around the scope. (Gun Talk Media, 2013)

Bibliography

Brown, Greg. “Does Scope Tube Size Matter?” Badass Optics. July 5th, 2020. https://www.badassoptic.com/does-scope-tube-size-matter/. 

Cuthbert, Simon. “Rifle Scope Objective Lens Diameter - Why & How Lens Size Matters.” Target Tamers. March 30th, 2023. https://www.targettamers.com/guides/rifle-scope-objective-lens-diameter/. 

Gun Talk Media. “Understanding Parallax with Leupold.” June 14th, 2013. https://www.youtube.com/watch?v=6ziKTDIMCig.