Diagnosing parallax–a lesson from Lucid Optics

I’ve been fortunate to attend the Blue August gun writers’ conference this week. In the process of learning about new products industry reps were there to promote, I also learned a few things about shooting. This one will be of interest to anyone who uses a magnifying scope. It was shared by Jason Wilson, founder and CEO of Lucid Optics, based in Riverton, Wyoming.
The correct definition of parallax involves more science than I can digest in a year. So here’s the Parallax for Dummies version: when viewing a target through multiple lenses, its real location may be different, by a few inches or even more, as compared to how it’s perceived by your eye.

A brief demonstration of parallax can be done right now. Put your hand in front of you, making a “V” with your thumb and forefinger. Through the bottom of the V, view an object across the room, like a doorknob. Focus on the V. Now, shift your focus to the doorknob. Notice how whatever you’re not primarily focused on appears to float a bit? Perhaps a duplicate image even appears.
Our eyes are incredible tools, and so are good quality scopes. But this bit of inaccuracy could result in a miss or an inhumane kill, so it must be addressed by the long range shooter.
Now that you’ve witnessed parallax sans scope, let’s diagnose it behind the glass using Wilson’s technique. This method assumes your scope is securely mounted to your rifle and zeroed for you, not some other shooter.
Make sure the rifle is supported on a bipod or other object and is stable. Pick a stationary target at midrange distance, about 300 yards. Make sure the picture is clear and in focus as you center the reticle on it. Now, keeping the rifle and scope perfectly still, move your head, keeping focus on the target. See how the target appears to move around? Repeat this head movement exercise, taking note of whether the reticle stays on the target and appears to move with it, or whether it remains in the center as the target “moves” around.
If the center of the reticle remains on target, moving in unison with it, you’re good to go. If the reticle and target separate, you’re experiencing parallax.
Wilson said that many people make the mistake of assuming the left-hand adjustment knob on their riflescope (if one exists) is a fine focusing knob. It’s actually there for parallax adjustment. If your scope has a parallax adjustment knob, repeat the parallax test as you continue turning it until the target and reticle images “float” as one.
Incidentally, the fine focus adjustment on most riflescopes is the small ring on the very rear of the optic, behind the magnification adjustment. My long-range shooting advisors recommend securing that ring with electrical tape once fine focus is achieved for you and your scope. That prevents unintentional turning of the ring as you carry the rifle afield.
As the owner of a Lucid Optics L7 scope, which was previously reviewed on GunCarrier and held up to some hard use over the summer, I was eager to meet the man behind the optics. It was a treat to take in a bit of Jason Wilson’s encyclopedic expertise on optics and their human interface. My scope doesn’t have a parallax adjustment, by the way, but Lucid Optics’ L5 models, with more magnification, do.