Top 5 Optic Myths Explained


On the surface, this seems like it makes sense. If you had a 2-foot diameter water pipe vs. a 1-foot diameter pipe, the 2 foot one is going to let more water through. But light is a weird thing, and there’s more going on inside your rifle scope than you may think.

The actual benefit of a larger maintube is more adjustment travel – plain and simple. The erector system (the part inside the scope that controls magnification and point-of-impact) moves around inside the maintube. With long-range shots, the bullet drops more the farther you shoot. Adjusting your elevation dial allows you to compensate for this bullet drop. The larger the maintube, the more adjustment you can dial into your elevation, which compensates for larger drops at farther distances.

The little-known fact is that it’s the erector system that limits how much light is getting to your eye. It also has a big effect on image quality.

Here’s a scenario that you may have run across – you have two different scopes from two different brands with similar specs. Both have the same magnification range, maintube diameter, and objective lens size. But brand A has 20 MOA less travel than brand B. How is that possible? Well you can’t cheat physics, so instead, some companies decrease the diameter of the erector system, thus providing you with more travel. Of course, the downside is that this also decrease the amount of light and the quality of the image that’s getting to your eye.

That’s why we didn’t skimp on the Mark 5HD’s maintube size. We decided to go with a 35mm maintube, so we could have the right amount of travel, while still preserving an incredibly bright and clear image with a larger diameter erector system.


Again, this seems like common sense. But the size of the objective lens is directly tied to the magnification range of the scope. Have you ever noticed how lower-magnification scopes usually have a small diameter objective lens, while high-magnification scopes have larger ones? That's because the combination of these specs is what creates the scope's exit pupil size.

The exit pupil is the disc of light that actually hits your eye. This disc needs to be the right size in order to have a bright, clear image all the way through the magnification range. You can visualize this by taking an un-mounted scope, holding it in your hand with the objective lens facing up. Put a white piece of paper on a table below it and shine a flashlight through the scope. Make sure the scope is the same distance away from the paper as it would be from your eye if you were shooting. With the light shining through the scope, you should see a disc of light hit the paper on the other side. Move the scope up and down to see how the disc goes in and out of focus. Adjust the magnification, and you’ll see the disc get bigger and smaller.

There’s also a very ease mathematical formula to figure out what size your exit pupil will be. It’s the diameter of the objective lens divided by the magnification. This will give you the exit pupil diameter in millimeters.


If you have a 1-4x20mm scope that's on 1x, the equation looks like 1/20 = 20mm exit pupil. If it’s on 4x, it would be 4/20 = 5mm exit pupil

Now let’s say you have a 3-18x44mm scope. If it were on 8x, the equation would be 8/44 = 5.5mm exit pupil. Almost the same as if the 1-4x scope was on 4x.

The other thing to consider is how much light your eye can physically use. It actually varies by age. When you’re young and your eyes are fresh and new, your pupils can dilate quite large, maybe to 7 or 8mm’s. But as you age, your eyes age, as well. Your average 35-year-old eye may only be able to dilate to 4 or 5mm’s. So yes, we could definitely create a scope that gives you a 30mm exit pupil, but your body wouldn’t actually be able to absorb all the light.


This myth seems to stem from the more traditional hunting crowd. It was a common practice back in the day to get a scope, mount it, sight it in at 100 yards and never touch the adjustments again.

While this isn’t a horrible thing to do (you’ll be able to hit the kill-zone of most animals out to about 400 yards), it definitely limits what you can do with the scope.

Adjustments on Leupold scopes are kind of like a car’s engine – they want to run. Actually, the first thing we tell customers to do on a new scope is run the adjustments back and forth for a few cycles to make sure all of the grease is evenly spread out – kind of like the break-in period on a car but much shorter.

We take it a step further with our Custom Dial System (CDS). This system is designed for you to dial the exact distance every time you shoot. So you’ll be dialing the elevation adjustment back and forth, depending on the yardage your shooting, for as long as you own the scope. Since our adjustments are precisely made and repeatable, you’ll have no issues with tracking and returning to zero.


Another common misconception that seems logical. The heavier something is the more durable it is; right? Most people think of a huge truck compared to a little compact car. Obviously, the truck can take more of a beating. But recoil energy on a rifle is different; it doesn’t like traveling through a dense mass.

When you pull the trigger on a rifle, the shot creates a lot of kinetic energy. That energy needs to go somewhere. It makes its way through the gun, up into the rings, and eventually into the scope. A lighter scope will actually disperse this kinetic energy more efficiently.

Think about a truck hitting a super-dense wall. The wall is going to transfer some of that energy back into the truck, but it’s also going to internalize a lot of it, which could cause damage. But if the wall was made of heavy-duty netting, the truck would receive minimal damage because the netting transfers that energy more efficiently, which prevents damage.

It’s the same concept with a scope. When a lighter rifle scope receives that wave of energy, it flexes in the rings, dispersing that energy more efficiently. Go watch a high-speed video of a rifle being shot, and you’ll see the scope flexing. The less mass the rifle scope actually has, the more efficiently it can do its job and the longer it’s going to last.


You’ve probably heard it before, “I need at least 25x to shoot 1000 yards,” or whatever your “long range” is. But the truth of the matter is that long shots can be taken with relatively low-magnification optics. Even a semi-proficient shooter can hit a man-sized target at 1000 yards with a 3-9x rifle scope. We've even seen shooters who can consistently hit 300-400-yard targets with 1x red dot sights. At the end of the day, skill and knowing your equipment can make up for the lack of magnification.

While it is nice to have that large magnification for long-range shots, the max power on your scope may not always be the best option. If someone’s shooting a 5-25x scope, they may actually be able to shoot more accurately on 20x, 18x, or even 12x.

When your image is magnified, it actually magnifies everything else, as well. So your breathing, involuntary movements, and the mirage all have a magnified effect on the image. When you knock the power back down a bit, everything can feel much more stable. You may surprise yourself with how accurately you can shoot on lower magnifications.

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