Dave Merrill of Breech Bang Clear explains that there is really no such thing as parallax free. He breaks it down rather simply and it is easy to grasp.
Here is a photo that illustrates how the reticle is reflected in the optic.
Most of the time a shooter will not experience much parallax shift if they have a good solid and consistent cheek weld. The issues comes down to unusual shooting positions and the focal length of the dot in relation to the target.
Here is a very simple yet clear demonstration of how this works.
How do manufacturers deal with parallax? Here is Merrill’s explanation.
Have you ever seen 1x RDS with a parallax adjustment turret? Me either. There are several different methodologies that manufacturers employ to reduce parallax. One of them is focusing at infinity. Remember that perceived movement at longer ranges is reduced. A dot focused at infinity will have less apparent movement, especially with targets further than 50m away or so, than a dot focused at a closer range. A red dot sight with a smaller objective window will also have less parallax, simply because your vantage point can only deviate so much before you’re out of the window entirely. Many reflector setups will utilize a Mangin mirror, which is a concave lens that helps to ensure the dot stays in line with the body itself. This setup is especially useful for reducing parallax from lateral movement, though they still remain susceptible to deviations in vertical movement. No doubt there are several more methods.
Merrill does test this himself. Using a picatinny rail, a vice and a camera sliding rig he sets up some red dots and a target out at 68m. Here are the optics he tested.
- Aimpoint Micro H1 (4 MOA)
- EOtech EXPS
- Trijicon MRO
- Leupold LCO
- Trijicon RMR 01 (3.25 MOA)
- $40 Tru-Glo Walmart Special
To check out Merrill’s article click here.