Home    Mission Statement RBA Section IR 50/50 Section ARA Section Worth Reading Scoring Program
Parallax with a clear image?
 “I focus the adjustable objective or side focus dial on my scope until I have a clear image of the objective, but I still see parallax when I move my head.?”
Often, people will pick up and use technical terms without really understanding their meaning. Take, for instance, parallax. How often have you heard people talk about parallax? Do you know what it means? Can you explain it to other shooters? If you can't, you're not alone. Many people are confused as to just what this term means. Quite simply, parallax is the situation that occurs when the reticle and the image are not in the same optical plane, causing the image to be unclear or to move in relation to the reticle.

The trick to parallax is focusing the reticle, which is about six inches from the shooters eye, and the objective (target), which is maybe 100 yards away. Try holding both of your thumbs out in front of you. Place one thumb at arms length and the other thumb right behind it about half way to your eye. Now, you should have your thumbs lined up in front of your eyes about a foot apart. If you move your head from left to right you will notice that the thumb closest to you appears to move across the image of the front thumb. That’s parallax. The front thumb represents the objective and the thumb closest you represents the reticle. The distance between the thumbs represents two optical planes.

Now try putting your thumbs side by side. When you move your head now you will see that neither thumb move in relation to the other. This is because they are both in the same optical plane. Notice that we don’t say that they are both in focus. It is possible to have no parallax even if the objective and the reticle are out of focus and appear fuzzy. What is critical to parallax is having both images on the same optical plane, wherever that plane may be as far as focus is concerned.

Most instances of parallax are caused by the objective being slightly out of focus, but this assumes that the reticle has been focus properly. It is also possible to have the objective in focus and not have the reticle focused and experience parallax.

“Wait a minute. How do I get rid of parallax in a fixed objective scope?” Great question! Fixed objective scopes have very deep field of focus. The focus of the objective, which is typically set at 150 yards, is much less critical than a variable objective scope and these scopes are usually lower magnification scopes where focus and the affects of parallax are much less. Also, the application of these lower magnification, fixed objective scopes (i.e. hunting) requires the least amount of shot to shot maintenance as possible. An adjustable objective set at 150 yards would greatly detract from that 75 yard snap shot at the whitetail that just jumped up in front of you.

With an adjustable objective scope the user has the ability to control the focus of both the reticle and the objective. The adjustable objective has a very shallow field of focus and is usually a higher magnification scope which both make the adjustment of the objective more critical. It also makes it more precise. AFTER you have PROPERLY set the reticle/eye piece/diopter adjustment the adjustable objective, whether objective dial or side focus, should be focused by looking through the scope at the objective.

MOST IMAGE AND PARALLAX PROBLEMS OCCUR FROM IMPROPER ADJUSTMENT OF THE RETICLE FOCUS. IF YOU HAVE ALREADY MADE THIS ADJUSTMENT AND THINK THAT YOU HAVE DONE IT CORRECTLY, SECOND GUESS YOURSELF.

Leupold

~