What is Parallax?
- Parallax is the visual difference of position and/or orientation of an object when it is perceived from two separate lines of sight.
Parallax in Rifle Scopes
Parallax in rifle scopes manifests as the reticle or crosshairs, 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.
I have also read in Webster's Unabridged Dictionary that "Parallax is the apparent displacement of an observed object due to a change in position of the observer".
In a well written article from John Barsness in the August 2010 issue of Guns Magazine, he uses this illustration to make it easier to understand:
"An easy demonstration of parallax can even be performed by the average couch potato. Look across the room at a stationary object, say the remote control you left beside the TV, where it isn't doing you any good. Hold up your hand and making a circle with the thumb and forefinger, look through the circle at the remote. Now holding your hand still, turn your head back and forth as if firmly telling your teenage daughter that no, she can't go on spring break in Daytona Beach. The TV remote will apparently move back and forth inside the finger-circle. That's parallax."
How important is it for big game hunters whose shots at whitetails, elk, moose, caribou under 200 yards and black bear over bait etc.? Most of us don't have to worry about it and some of us have never heard about it.
Even if your shot is left or right 3 to 5 inches of center on a pie plate set of lungs on a broadside or slightly quartering away animal, you are still in the kill zone. Many scopes have NO parallax adjustment and I have never missed not having it. Try and keep your EYE centered behind the scope which is where you get a FULL FIELD OF VIEW ANYWAY, and parallax in most cases is a NON-issue for big game hunting. For the lion's share of big game shooting, especially N/E whitetails under 200 yards, it is not a concern. I am fond of the Bushnell Elite 3200 series of rifle scopes and per their own literature parallax is factory set under 11X at 100 yards. See below:
Parallax
A condition that occurs when the image of the target is not focused precisely on the reticle plane. Parallax is visible as an apparent movement between the reticle and the target when the shooter moves their head or, in extreme cases, as an out-of-focus image. Bushnell center fire rifle scopes under 11x are factory-set parallax-free at 100 yards; rim fire and shotgun scopes at 50 yards. Scopes of 11x or more have an adjustable objective to adjust for parallax.
Most rimfire rifle scopes are set parallax free at 50 yards and most reputable big game scopes are pre-set at 100 to 150 yards.
What I FEEL is a greater concern for most hunters after handling hundreds of other shooter's rifles at the range is that their scopes are often not aligned properly and is in fact canted to one side of the other. The scope is "Listing to Port or Starboard" as we used to say in the NAVY. I believe what causes more missed shots than the parallax issue is a scope that is canted to the right or left of center. If it is sighted in with a scope that is canted and then in the heat and excitement of the hunt you take a 150 yard or 200 yard shot and your eye naturally aligns the scope properly it is going to throw you shot right or left by several inches. If your eye is not centered in the scope and your are not getting a full field of view to boot, you might completely miss an animal.
For more valuable information on PARALLAX see the links below:
Dan
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