What is Parallax in Rifle Scopes?
Posted: Fri Apr 26, 2013 11:41 am
What is Parallax in Rifle Scopes?
Parallax is an optical issue that comes into play with any telescopic device, including gun scopes. For shooters looking for precision at mid ranges (100yds to 300yds), parallax is a serious issue. While it is not a standard feature, many scopes come with parallax compensators.
You can check the parallax of any scope by sighting an object at normal shooting distance, preferably outdoors by moving your eye side to side (then up and down), as far as you can, keeping the sighted object within the field of view.
THE APPARENT MOVEMENT OF THE RETICULE IN RELATION THE TARGET IS KNOWN AS PARALLAX.
HOW TO ADJUST THE PARALLAX ON RIFLE SCOPES
Parallax is the visual difference of position of an object when it is perceived from two separate lines of sight. Parallax in rifle scopes happens as the reticule or cross-hairs, appearing to be on different points on the target due to slight changes in the position of the eye, relative to the scope's eyepiece.
Parallax is naturally a problem for some kinds of shooting, as these slight changes can put a pellet / bullet off course. However, for most shooting purposes, parallax is not an issue, and most scopes do not have parallax compensators for this reason.
The odd thing about parallax and shooting is that the effects are often more noticeable in short-to-medium ranges than for long-range targets.
Some rifle scopes compensate for parallax by using a mechanism that puts both the target image and the reticule on the same optical plane. There are two ways of doing this and it’s called "AO" which stands for “ADJUSTABLE OBJECTIVE”
HOW TO USE AN ADJUSTABLE OBJECTIVE IN A SCOPE
You adjust it to get greater aiming precision. Parallax correction helps you sharpen your aiming because you always see the target from the same perspective.
HOW TO DO IT?
Look through the scope at the target and twist the ‘AO’ adjustment ring or knob until the target appears as sharp as you can make it. At that point, you've removed all the parallax that you possibly can. Even the best scopes will have some parallax left after adjustment, which is why your cheek placement on the stock is so important.
If your eye is always in the same position relative to the scope, there won't be a parallax problem. The problem comes when your eye isn't always in the same position. Small variations in placement introduce parallax, even in scopes with parallax adjustment.
EXAMPLE
Close one eye and point your index finger at some distant object. Hold your finger steady on that object and switch eyes. The finger will shift - That's because both your eyes cannot look at the same thing from the same perspective. The distance that they are separated in your head affects the amount of parallax they induce.
Now, imagine that your finger is the barrel of an air-gun and your eyes are the sights. How could you hit anything if the target image keeps moving relative to the sights? You would pick one place to look from (look from one eye, only) and always use that place to line up the sights.
So when you sight in, you will adjust the sights until that picture, seen from just one place, produces hits where you want them. In an air rifle it means always placing your head at the same place on the stock so your eye will be in the same place, relative to the sights. This eliminates parallax from any scope, even one that is not adjusted for the range you are shooting.
Scopes with parallax adjustment take care of the largest share of parallax removal however the shooter has to be careful when placing his cheek exactly on the stock each time.
The focusing function ‘AO’ works like the rangefinder of a 35mm SLR camera. When the target is in sharpest focus, the scope is set to the near exact distance to the target. This in fact is the closest you can get in removing parallax.
> BTW - My sincere advice for all those planning to buy scopes for ARs would be to - Insist on a Scope that's AR rated with AO adjustment facility. A fixed power scope with 4X x 32 is adequate for most spring powered ARs while a Variable Scope such as 2-7 x 40 or 3-9 x 40 are recommended for PCPs & magnums.
HAPPY SHOOTING!!!
Briha
Parallax is an optical issue that comes into play with any telescopic device, including gun scopes. For shooters looking for precision at mid ranges (100yds to 300yds), parallax is a serious issue. While it is not a standard feature, many scopes come with parallax compensators.
You can check the parallax of any scope by sighting an object at normal shooting distance, preferably outdoors by moving your eye side to side (then up and down), as far as you can, keeping the sighted object within the field of view.
THE APPARENT MOVEMENT OF THE RETICULE IN RELATION THE TARGET IS KNOWN AS PARALLAX.
HOW TO ADJUST THE PARALLAX ON RIFLE SCOPES
Parallax is the visual difference of position of an object when it is perceived from two separate lines of sight. Parallax in rifle scopes happens as the reticule or cross-hairs, appearing to be on different points on the target due to slight changes in the position of the eye, relative to the scope's eyepiece.
Parallax is naturally a problem for some kinds of shooting, as these slight changes can put a pellet / bullet off course. However, for most shooting purposes, parallax is not an issue, and most scopes do not have parallax compensators for this reason.
The odd thing about parallax and shooting is that the effects are often more noticeable in short-to-medium ranges than for long-range targets.
Some rifle scopes compensate for parallax by using a mechanism that puts both the target image and the reticule on the same optical plane. There are two ways of doing this and it’s called "AO" which stands for “ADJUSTABLE OBJECTIVE”
HOW TO USE AN ADJUSTABLE OBJECTIVE IN A SCOPE
You adjust it to get greater aiming precision. Parallax correction helps you sharpen your aiming because you always see the target from the same perspective.
HOW TO DO IT?
Look through the scope at the target and twist the ‘AO’ adjustment ring or knob until the target appears as sharp as you can make it. At that point, you've removed all the parallax that you possibly can. Even the best scopes will have some parallax left after adjustment, which is why your cheek placement on the stock is so important.
If your eye is always in the same position relative to the scope, there won't be a parallax problem. The problem comes when your eye isn't always in the same position. Small variations in placement introduce parallax, even in scopes with parallax adjustment.
EXAMPLE
Close one eye and point your index finger at some distant object. Hold your finger steady on that object and switch eyes. The finger will shift - That's because both your eyes cannot look at the same thing from the same perspective. The distance that they are separated in your head affects the amount of parallax they induce.
Now, imagine that your finger is the barrel of an air-gun and your eyes are the sights. How could you hit anything if the target image keeps moving relative to the sights? You would pick one place to look from (look from one eye, only) and always use that place to line up the sights.
So when you sight in, you will adjust the sights until that picture, seen from just one place, produces hits where you want them. In an air rifle it means always placing your head at the same place on the stock so your eye will be in the same place, relative to the sights. This eliminates parallax from any scope, even one that is not adjusted for the range you are shooting.
Scopes with parallax adjustment take care of the largest share of parallax removal however the shooter has to be careful when placing his cheek exactly on the stock each time.
The focusing function ‘AO’ works like the rangefinder of a 35mm SLR camera. When the target is in sharpest focus, the scope is set to the near exact distance to the target. This in fact is the closest you can get in removing parallax.
> BTW - My sincere advice for all those planning to buy scopes for ARs would be to - Insist on a Scope that's AR rated with AO adjustment facility. A fixed power scope with 4X x 32 is adequate for most spring powered ARs while a Variable Scope such as 2-7 x 40 or 3-9 x 40 are recommended for PCPs & magnums.
HAPPY SHOOTING!!!
Briha