What does 3x9x40 mean on a rifle Scope?
When shopping for a rifle scope, you may come across specifications such as 3x9x40, which can be confusing for beginners. In this article, we will break down what these numbers mean and provide a comprehensive understanding of rifle scope magnification and optics.
What does the number mean?
A rifle scope’s specifications typically include three numbers: the first number represents the magnification, the second number represents the objective lens size, and the third number represents the exit pupil. In this case, 3x9x40 refers to a scope with the following characteristics:
- Magnification: 3x (three times)
- Objective Lens Size: 9 (in inches or mm)
- Exit Pupil: 40 (in mm)
What is magnification?
Magnification is the ability of the scope to enlarge the target or image, making it easier to aim and shoot accurately. The higher the magnification, the more detailed the image will be. However, high magnification also comes with some limitations, such as:
• Shake and vibration: High magnification can exacerbate any shake or vibration, making it harder to hold steady.
• Limited light transmission: High magnification can also reduce the amount of light entering the scope, making it more difficult to shoot in low-light conditions.
• Increased weight: High-magnification scopes are often heavier and bulkier due to the increased lens complexity.
What is the objective lens size?
The objective lens size refers to the diameter of the lens that gathers light from the target. A larger objective lens can:
• Admit more light: A larger objective lens allows more light to enter the scope, making it suitable for low-light conditions.
• Provide a clearer image: A larger objective lens can also provide a clearer image, especially at lower magnifications.
• Reduce distortion: A larger objective lens can help reduce distortion and aberrations, resulting in a sharper image.
What is the exit pupil?
The exit pupil is the diameter of the light beam that exits the scope, measured in mm. A larger exit pupil can:
• Reduce eye relief: A larger exit pupil can reduce eye relief, making it more comfortable to shoot with glasses or goggles.
• Increase brightness: A larger exit pupil can also increase the brightness of the image, making it easier to aim in low-light conditions.
• Improve versatility: A larger exit pupil can make the scope more versatile, allowing for use with different types of glasses or goggles.
Understanding the trade-offs
When choosing a rifle scope, it’s essential to understand the trade-offs between magnification, objective lens size, and exit pupil. Here are some key points to consider:
• Lower magnification, higher objective lens size: A scope with lower magnification (e.g., 3x) can be paired with a larger objective lens size (e.g., 40mm) for improved light transmission and image clarity.
• Higher magnification, smaller objective lens size: A scope with higher magnification (e.g., 12x) may require a smaller objective lens size (e.g., 20mm) to maintain a reasonable weight and size.
• Compromising on exit pupil: A scope with a larger exit pupil may be less suitable for use with glasses or goggles, but may provide improved brightness and versatility.
Conclusion
In conclusion, the specifications 3x9x40 on a rifle scope refer to a scope with a magnification of 3x, an objective lens size of 9 inches, and an exit pupil of 40 mm. Understanding the importance of magnification, objective lens size, and exit pupil can help you choose the right scope for your specific needs and preferences. Whether you’re a beginner or an experienced shooter, a rifle scope with the right specifications can make all the difference in your shooting accuracy and performance.
