The Importance of Objective Lens Diameter How to Choose the Best Riflescope for Your Hunting Trip


When picking the ideal riflescope for your next hunting trip, it's important to consider a few factors. These include the size of the objective lens. Knowing what size lens fits best and which magnification is suitable for different distances will help you select the right scope for a successful hunt.

The objective lens is the part of a riflescope that faces forward. It stops dust and debris from getting in your eye while aiming. It also focuses light and produces images inside the scope. The objective has two measurements – diameter (in millimeters) and focal length (in inches). This tells you how much light can be collected by a specific scope. In addition, lenses come with different zoom powers – how much they magnify. This helps you stay focused when shooting over various distances.

By understanding the type of lenses, as well as their practical uses, you can make an informed decision about which riflescope is best for you. This will help you make every shot count when you go hunting.

Objective Lens Diameter Explained

The size of the objective lens diameter is critical when selecting the right riflescope. This is because it controls the amount of light that enters the scope. This affects your sight picture and shooting accuracy.

Let's delve into how the size of the objective lens diameter impacts your riflescope performance:

What is objective lens diameter?

Objective lens diameter is a must-know when buying a riflescope for hunting. It's usually between 32 and 50 mm. The objective lens is the opening that lets light in from what you're viewing. The bigger the lens, the brighter and clearer the image. Also, it determines how powerful of magnification you can get out of your optics system. Bigger lenses allow greater magnifications, helping you spot targets at further distances with better clarity.

It is important to understand the characteristics of each size and what they bring to various types of shooting scenarios, to make sure your investment will meet your needs:

  • Objective lens diameter is usually between 32 and 50 mm.
  • The bigger the lens, the brighter and clearer the image.
  • Bigger lenses allow greater magnifications, helping you spot targets at further distances with better clarity.

How does it affect performance?

Objective lens diameter hugely affects a riflescope's performance. It influences the size of the front lens element, which impacts light transmission and image-forming capabilities. A larger diameter lets more light in, producing brighter images. Whereas, a smaller diameter transmits less light, making the image appear darker.

The size also affects image quality. A larger diameter provides greater magnification power, enabling you to see objects at greater distances with clearer details. Smaller scopes may weigh less, but if you need long range shots or will be hunting in different conditions, you should consider investing in a bigger objective lens. This way, you'll get superior zoom capabilities and brighter images at longer distances.

What is the ideal objective lens diameter?

Objective lens diameter (known as obj or OD) is measured in millimeters. The more light it allows in, the brighter and more detailed the image will be. But, it also adds weight, size, cost, and glare.

For hunting, a 50mm or 56mm lens diameter is best. It provides enough light while keeping the size and weight reasonable.

When deciding the size, consider the optic you'll mount on your rifle. For low powered scopes like a fixed 4x, 40mm is enough. For mid-to-high magnification scopes (3-9x), 42mm is ideal. For 6-20×50, a 56mm lens diameter is best. It provides clear images without making the gun too bulky.

Types of Riflescopes

Riflescopes are a must-have for hunting. There's a range of types, from classic fixed magnification to digital and variable ones. A key factor to consider is the size of the objective lens. It dictates the light and image quality the scope can take in. So, size really matters when it comes to selecting the right scope.

Fixed Power Riflescopes

Fixed power riflescopes are referred to as “fixed” because the magnification does not change. They are often less expensive than variable power scopes, making them a great choice for beginners or casual shooters. Plus, they come with larger lenses that let in more light and provide a clearer image. Fixed power scopes come in different objective lens diameters (from 24mm to 56mm). This makes them more affordable and versatile than variable scopes.

A fixed scope has many advantages:

  • It is more durable and easier to use than variable scopes, which have more moving parts that can get worn out.
  • It has fewer internal moving parts so it is less likely to fail.
  • It is lighter and more compact than variable optics, so they can reduce rifle weight.
  • Many professional hunters prefer higher magnification levels, so they can take long range shots accurately without sacrificing quality.

Variable Power Riflescopes

Variable power riflescopes are popular. They let you adjust the magnification of the scope. You can focus on the target better, and get more details of it. The zoom range is usually 4X to 12X. You use a dial on one side of the scope to adjust the zoom. Variable power scopes have adjustable reticles. It helps you aim more precisely and accurately when shooting from long distances.

Variable power scopes have fixed or variable objective lens sizes. Usually, the lens size is between 40mm-50mm. Bigger lenses let in more light for clarity and accuracy. However, smaller ones are better for shooters who hunt from trees or other tight spaces. They make it easier to stay steady and reduce fatigue.

Factors to Consider When Choosing a Riflescope

Searching for a riflescope for hunting? Understand the factors that impact its quality. One of the main ones is Objective Lens Diameter (OLD). OLD offers light transmission and image resolution. Therefore, choose the right diameter for your scope. Here, we'll delve into the importance of OLD and how to pick the best riflescope for your needs.


Magnification is a key factor when picking a riflescope. It influences your accuracy with far-away targets. Generally, you want higher magnification levels for greater distances.

For example, a 6-24x50mm scope is great for long range accuracy, since it can magnify from 6x to 24x.

Many optics makers offer rifle scopes with various magnifications, such as:

  • 4-12x40mm
  • 4-16x44mm
  • 6-18x40mm

When deciding the right scope magnifications for you, take into account terrain, weather, wind and light. Plus, techniques like parallax adjustment can greatly increase shooting precision. So, choosing an appropriate scope magnification will help you engage longer shots with more accuracy.

Lens Coating

Lens coating is a key point when picking the right riflescope for a hunt. It keeps out external elements and increases light transmission for better picture resolution, brightness, contrast and color accuracy.

Full multi-coatings have multiple layers of anti-reflective coating applied to all optical lens elements. This helps to let in maximum light, and also makes them resistant to dirt, debris, abrasion and chemicals.

Multi-coated lenses have several layers on top of one surface. This cuts down glare, while allowing in enough light to boost brightness and reduce chromatic aberration. Single coated lenses have one layer which slightly reduces glare, and also boosts image resolution in low light.

It's important to make sure the scope is waterproof, fogproof and robust enough for the environment – especially in harsh weather conditions with gusts of wind or dust which could affect visibility.

Field of View

Field of view (FOV) is a key factor when selecting a riflescope. It's the amount of visible area seen through the scope and is measured at a given distance and magnification. Scopes with larger objectives generally have a larger FOV than smaller lenses. For instance, an 8x50mm lens has a wider FOV than a 4x32mm.

Boosting the FOV is useful. You can scan for game or target without moving the rifle. It helps you spot objects in relation to their surroundings quickly. Also, it reduces the “tunnel vision” feeling of things outside the scope.

When shopping for optics, get a scope with generous eye relief (around 3-5 inches) and adjustable zoom. Higher magnification reduces the FOV. Read the manufacturer's specifications to know the magnification range and FOV at those settings.


Lens diameter isn't all you need to think about when buying a riflescope. The reticle, or “crosshairs,” is essential too. It helps the shooter aim and shows where shots will land. Different reticles have different visibility and accuracy.

Types of reticles include:

  • Duplex: Thin and thick lines for visibility and aim at short distances.
  • Mil-Dot: Dots in a circle pattern around the crosshair. Good for 100-400 yards.
  • Illuminated: Adjustable light for low light conditions.
  • Target/Post: Hash marks across both sides of the crosshairs. Helps with shot adjustments.

Choose wisely to get the best shooting experience!

Eye Relief

Eye relief is the most important factor when choosing a riflescope. It is the distance from the rear lens to your eye when you look through the scope. This helps determine comfort while shooting. The more eye relief, the less recoil impact on your face and eyes. If the scope has little eye relief and is mounted too far back, there could be an uncomfortable experience or even injury.

Different scopes have different eye relief, depending on types and magnification levels. Low magnification usually has longer eye relief, but as you increase magnification, you may need to adjust the position to get an optimal view. Eyepiece design can also be a factor. A fast focus or adjustable eyepiece makes it easy to make a change when needed.

When choosing a scope for hunting or target shooting, consider the following:

  • Measure several different scopes and get a feel for how they mount.
  • Check any warranties associated with the product to ensure they are worth their value and backed by the manufacturer.


Finally, the size of your riflescope's objective lens is essential. Bigger diameters give a wide field of view, better light transmission, and clearer pics. Smaller lenses mean less noise and more coverage. It depends on what you need. So, consider the pros and cons before choosing. Find the best balance between performance and cost for your hunting conditions.

Frequently Asked Questions

Q: What is the importance of objective lens diameter?

A: The objective lens diameter is important because it determines the amount of light that enters a riflescope. The larger the diameter, the more light is able to enter, which results in brighter, clearer images.

Q: How do I choose the best rifle scope for my hunting trip?

A: When choosing the best rifle scope for your hunting trip, you should consider the type of game you'll be hunting and the environment you'll be hunting in. For example, if you'll be hunting in low-light conditions, you should opt for a scope with a larger objective lens diameter to allow more light in. Additionally, you should also consider the type of reticle and magnification levels that best suits your needs.

Q: What other factors should I consider when choosing a rifle scope?

A: Other factors to consider include the scope's durability and the type of coating applied to the lenses. Durability is important, as you want to make sure your scope can withstand rough conditions. The type of coating applied to the lenses can affect image clarity and reduce glare, so it's important to look for a scope with a quality lens coating.

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