From Zero Compromise Optics:
Setting Your Diopter
We’re often asked about setting the diopter on ZCO rifle scopes. There are a lot of techniques that people use to accomplish this, and we’ve tested numerous popular techniques to find the overall best method for optical performance throughout the entire magnification range.
Over the past few years, we have encountered many shooters not taking the necessary time to properly set their diopter to their eye. Generally, shooters adjust it once at the highest magnification until the reticle appears clear, then leave it set there. They then experience odd optical properties, or the sight image just isn’t optimized, due to an improperly adjusted diopter. Younger eyes are often better at rapidly adjusting to focus a reticle image when improperly set, leaving eye muscles having to continually work the entire time the shooter’s looking through the scope, resulting in increasing eye fatigue. By taking time to properly adjust the diopter, a much better optical performance of the scope will be realized, with the shooter experiencing much less eye fatigue over the duration of a day of shooting.
The biggest difference with our recommended method for adjusting your diopter is to do this on a reduced magnification setting. We suggest using around 8X magnification instead of the more commonly suggested maximum magnification for your scope. Employing a smaller but still very visible reticle prevents your eye from over-compensating and adjusting to focus on smaller details, leading to a more precise diopter setting.
Our method also differs from a common method of going directly to the first “focused” setting once, then wiggling the diopter back and forth in tiny increments. Again, your eye muscles will usually compensate for small errors in the proper setting for an individual’s eye. Our method requires you to go past the focused setting in one direction or the other, then back the other direction again until just past the focused point again. You then simply turn the diopter back immediately to the focus point for the reticle. This helps build the eye, brain, and hand memory for where the true focus point is for the reticle.
Therefore, please follow the recommended steps for adjusting the diopter on your ZCO riflescope for your specific scope and eye. This will give you the best optical performance of your scope and make use of the scope much more pleasing throughout the entirety of a day of shooting.
1. Set your scope to 8X power on the magnification ring. This will make your eye work to see the reticle, but you should still be able to clearly make out the fine graduations on the reticle.
2. Set the parallax to infinity.
3. Loosen the lock ring on the diopter adjustment, turning it counterclockwise 2-3 turns.
4. Looking through the scope at an all-white background, with a moderately fast speed, turn the diopter adjustment until the reticle goes out of focus. The speed of turning should be fast enough that your eye isn’t able to compensate to focus the reticle.
5. Next, turn the diopter back the other way at a moderately fast pace, again past the focus point one more time. Your eye/hand/brain will have a very good idea at which point the diopter needs to be for an in-focus setting.
6. Now, at a moderately fast pace, turn the diopter back toward the in-focus point until the reticle becomes clear and sharp.
7. You should now be able to look away from the reticle for a few moments and when you glance through the scope again, the reticle should be perfectly focused. Lock the diopter by turning the lock ring clockwise.
8. Your diopter will now provide a perfectly focused reticle throughout the entire magnification range giving you the best optical performance.