The Ultimate Guide to Objective Lens Diameter How to Choose the Perfect Riflescope for Your Needs


Puzzling over the right scope for you? Don't worry – objective lens diameter is key to finding the perfect scope! What is it? Why does it matter? We've got the answers. Read on to learn all about objective lens diameter and how to choose the right scope for your needs.

What is an Objective Lens Diameter?

The objective lens diameter of a riflescope is an important factor when it comes to choosing the right scope. This measurement is usually in millimeters, and it decides how much light enters the scope when shooting at different distances. The bigger the objective lens diameter, the more light, resulting in better image clarity even with long-range shots.

But, there are drawbacks. Having a large objective lens adds weight and size to the scope. Too large of an objective lens can lead to problems like decreasing efficiency in low-light conditions, needing a tripod for higher magnifications, expensive lenses, and difficulty with small mounts like on rimfire rifles or shotguns.

Finding the right size for any rifle depends on

  • shooting distance
  • type of reticle
  • eye relief from recoil
  • and other factors

It's up to you to decide which mix of features is best for you, considering your budget. We're here to help make the right decision!

Understanding the Benefits of a Larger Objective Lens Diameter

When it comes to selecting a riflescope, objective lens diameter is key. It affects how much light reaches your eye and consequently the brightness, clarity and resolution of the image. Therefore, a larger diameter is typically recommended.

A larger diameter also helps reduce chromatic aberration. This is when light is unable to focus in the same plane, producing blurry or distorted images. This is prevented due to the higher light transmission rate.

Moreover, larger lenses increase field-of-view and exit pupil size. Field-of-view is the width of the area you can see, while exit pupil size dictates how bright it appears. This makes a larger lens perfect for activities like varmint hunting or precision shooting as you can get a better view of your target and still have a bright and clear image.

How to Choose the Right Objective Lens Diameter

Choosing the perfect riflescope for your needs requires knowing the Objective Lens Diameter (OLD). OLD size determines how much light it can gather and the sharpness of the image. This guide outlines the key aspects of OLD and how to select the right one.

Consider Your Shooting Distance

When selecting an objective lens diameter for your rifle, think about the distance you're shooting. If it's far, opt for a large lens. It'll capture more light and give better resolution. Plus, a large lens has more light transmission and a wider FOV – both important for accuracy at a distance.

On the other hand, if you're shooting close-up, a smaller lens is best. Too much glare will distort the image. Smaller lenses also have more magnification power but less size/weight.

If you're doing close-mid range shooting, look for adjustable lenses with zoom rings that can switch between 1x-4x or 3x-9x. This way, you get the optical power needed without extra weight.

Consider Your Rifle’s Caliber

Caliber is key when it comes to measuring the size of the objective lens. If you have a larger caliber rifle, you'll need a bigger objective lens. This is because more recoil is created from the larger caliber rounds, so you need a large enough scope to absorb the force without damaging it. But for smaller calibers, you won't need such a large objective lens.

To work out the size of your objective lens, you can use this equation – Objective Lens Diameter (mm) = (Caliber x 25) + 5. This helps to make the brightness and clarity of your view clearer. However, it's best to get a scope designed for your rifle, to ensure the best performance.

Consider Your Hunting Style

When picking the right objective lens diameter, your hunting style is key. Varmint shooting requires a small, portable scope with an objective lens diameter of 34mm or less. A scope with a 22mm diameter should give you clear images with no eyestrain. Big game in low light needs a bigger objective lens, from 42mm up to 56mm.

Bigger lenses will give you brighter images, a wider field-of-view, and more eye relief. Pick the size that suits your needs; if you need more brightness, go bigger; if you need portability, pick something smaller that still works well.

Consider Your Budget

When picking the right objective lens size for your riflescope, budget matters most. The size of the lens affects its cost. So, decide how much you can afford. Smaller lenses cost less. Bigger lenses cost more.

Apart from budget, keep other things in mind. Think about how wide or narrow of a field of view you want. That'll decide the size of the lens. Plus, ensure the reticle and other features like eye relief and parallax adjustment suit your rifle and shooting style before selecting the right lens size.


Thus, picking the right objective lens size for your rifle scope can be tricky. But, if you take into account factors like the environment and what you're aiming at, you can decide on the ideal scope for you. This article has given you a summary of the pros and cons of objective lens size to help you make an educated decision.

Summary of Key Points

This guide showed why objective lens diameter is important. It can affect image sharpness, brightness and more. Here are some key points to remember:

  • Bigger lenses for higher magnifications give brighter images in low light.
  • DiamondCoat and Enhanced Multicoating can fight glare, so use them if hunting in low light.
  • Longer eye relief helps if you often press against the eyepiece.
  • You can choose between vanguard (41mm or more), standard (30mm-40mm), mid-sized (25mm-29mm) and small (less than 25mm) lens sizes.
  • Which lenses you choose depends on where you are hunting and your preferences.

Frequently Asked Questions

Q: What is an objective lens diameter?

A: An objective lens diameter is the size of the objective lens, or front lens, of a riflescope. It is measured in millimeters, and the larger the objective lens diameter, the more light it can gather, resulting in a brighter image for the shooter.

Q: What are the benefits of a larger objective lens diameter?

A: A larger objective lens diameter has several benefits. First, it will provide a brighter image in low light conditions, allowing the shooter to see more clearly. Second, a larger objective lens diameter will provide a wider field of view, or the amount of the target area that can be seen at one time. Third, a larger objective lens diameter will also provide a greater magnification range, allowing the shooter to more accurately target distant objects.

Q: How do I know what objective lens diameter is right for me?

A: Choosing the right objective lens diameter for your needs depends on several factors. Firstly, consider the type of shooting you will be doing – if you are shooting at targets at long distances, you will need a higher magnification and a larger objective lens diameter. Secondly, consider the light conditions you will be shooting in – if you are shooting in low light conditions, you will need a larger objective lens diameter to gather more light. Finally, consider the type of rifle you will be using – a larger objective lens diameter typically requires a larger mounting system, which may be incompatible with some rifles.

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