What is Rifle Scope Parallax Adjustment
There is a certain obsession over parallax “focus” for some scope users. Often justified, sometimes not!
But what is this parallax “focus” thing all about?
For starters lets get one thing technically straight right away. It is NOT parallax focus. It is Parallax Correction.
Often referred to as focus as it being incorrect will manifest as a focus issue. But it is NOT a focus tool. Be one of the pro team and start calling it parallax correction today!
Parallax effect is the term that describes the difference in angles between objects that are seen up close and those seen far away. When you look at telephone poles passing by on the side of the road, those closest to your car seem to pass very fast, while the ones far away seem to go very slow. That difference is due to the parallax effect.
The reticle in your scope is like a telephone pole that's very close. If you move your head on the stock while watching the target through the scope the reticle may seem to move, wobble or blur against the target. That affects where you perceive the aim point to be, and that affects your accuracy. Parallax correction adjustment reduces this phenomenon to the greatest extent possible.
Parallax correction therefore is a must for anyone attempting to use either a high magnification scope, shooting drastically different yardages with the same scope or anyone attempting to shoot at extremely close ranges or extremely long ranges. Especially so if it is a combination of these factors.
Important note on parallax adjustment versus regular ocular focus
A common mistake is to use the parallax adjustment in an attempt to focus the reticle. The ocular end (eye piece) has a focus for the reticle. That is the sole purpose of the ocular focus. Returns have been caused by users attempting to use the reticle focus as an image focus and or using the parallax adjustment as a reticle focus. If done incorrectly the result will be poor clarity and blurry vision.
First action - Use the ocular focus to focus the reticle and only focus the reticle while looking through the scope at the sky. This will keep you from trying to focus an object instead of the reticle.
Ocular Focus (eyepiece) adjusts the scope to the individual shooter's eye... this is a one time adjustment. (For wearers of prescription lenses this could be a multiple procedure event if new prescription arrive.) The purpose of this adjustment is to adjust the scope so that the image of the reticle (crosshairs) is properly aligned with the back of the shooters eye.
Parallax adjusts the target to the reticle (crosshair). The target image and the reticle must be on the same focal plane within the scope or there is room for apparent movement of the reticle on the target when the shooters eye moves (or is positioned differently at the scope).
Tactical style scopes are not usually supplied with parallax adjustment because the exact range of the target can never be anticipated. Scopes of lower magnification are not usually supplied with parallax adjustment either, because at lower powers the amount of parallax is so small as to have no importance for practical, fast target acquisition.
Parallax focus adjusts the target to the reticle (crosshair). The target image and the reticle must be on the same focal plane within the scope or there is room for apparent movement of the reticle on the target when the shooters eye moves (or is positioned differently at the scope).
Tactical style scopes are not usually supplied with parallax adjustment because the exact range of the target can never be anticipated. Scopes of lower magnification are not usually supplied with parallax adjustment either, because at lower powers the amount of parallax is so small as to have no importance for practical, fast target acquisition.