First vs Second Focal Plane Optics, By Michael Baccellieri

Article By Michael Baccellieri, Leupold Product Applications Training Coordinator

All Photos Credit: Talus Creative

A lot of folks in this industry ask which is better, first or second focal plane. But the truth is it’s simply a matter of finding the right tool for the right job. Neither one is better than the other. They both have pros and cons based on the application of the system. Understanding the difference between the two and their benefits can make all the difference when purchasing an optic. Many shooters look at first focal plane as strictly a tactical optic, while second focal plane is only for hunting. What we will discuss in this article is the application of the components in an optic. This is defined by the understanding of what “components” or feature sets will best suit the needs of the shooter. So let’s begin by breaking down the differences between the focal planes themselves.

What Are Focal Planes?

There are two distinct locations or “planes” in an optic where all the lights and colors that move through the optical system converge down to a single finite point, thereby creating a real image for the shooter’s eye to see and their brain to compute what they are looking at. These two points are called focal planes. Every variable power optic has both a first and a second focal plane. Either one of these locations can be the housing area for a reticle. This is why we refer to a scope as a first or second focal plane optic. We are specifically referring to the location of the reticle within the scope.

Inside the erector tube of the scope, there are two erector cells. These lenses move forward and back as the shooter rotates the power selector ring, causing the image to grow and shrink. The erector cells will magnify and de-magnify anything that is in front of them. This is how the magnification in the scope works. If the reticle is housed in the first focal plane location, then the reticle will change magnification in perfect relation to the image as it is located in front of the erector cells. If the reticle is housed in the second focal plane location, then the reticle will remain a single size while the image changes throughout the magnification range. This is very important to understand if the reticle has angular unit of measure subtensions added to it (Mils or MOA).

In a first focal plane scope, the Mil/MOA lines will be accurate and true throughout the entire magnification range. In a second focal plane scope, the subtensions will only be accurate on a specific magnification, typically the maximum magnification. As an example, if you are using a second focal plane scope with a magnification of 5x-25x with a Mil-based reticle, then on 25x each Mil is truly a Mil. But if you dropped the magnification down to 15x — exactly half the magnification range — then each Mil will now equal two Mils due to the fact that you have shrunk the image to half the size in relation to the reticle.

What’s Better for My Needs?

This really comes down to the application. The primary application that necessitates first focal plane optics is a style of shooting called “hold-off”. This is where the shooter will simply hold high for elevation and hold left or right to compensate for wind. If the shooter needs to be able to maintain a lower magnification for a larger field of view and still use the Mil/MOA reticle to hold-off shoot, a first focal plane scope would be the best choice. Most hunters, military, and law enforcement shooters move, hunt or fight with the optic on the lowest power setting. This is specifically to have the largest field of view and exit pupil available to them for rapid deployment of their firearm. If a hunter is stalking in tight, thick brush, chances are the shot will be taken from a relatively close distance. In the U.S. in 2016, the average law enforcement sniper shot was taken at fifty-seven yards. In both cases, it would be safe to say that the shooter would primarily live in a lower magnification setting. In these two examples, if the shooters were using a first focal plane scope, they would not have a bold, usable reticle available to them as the reticle would shrink down with the magnification. So for tight country hunting and for most of the law enforcement sniper community, a second focal plane would be an optimum choice.

If, however, the hunter is in wide open country, or the sniper is military as opposed to law enforcement, then hold-off shooting will be a big part, if not the primary method of engagement. Whether it is dialing for elevation and holding for wind, or holding for both windage and elevation, the first focal plane scope becomes a much more usable tool.

When looking to purchase a new optic for a firearm, consider the application and choose accordingly. Do not let the masses convince you that one is “better” than the other. It is simply a matter of the proper application of components.

Posted by Adam Janke