What are the main prism types used in monoculars, spotting scopes, and rangefinders, and which are the most expensive?

1. Porro Prisms:

• Porro Prism (Classic Porro Prism): This is a traditional prism design that uses two prisms to provide a wide field of view and good depth perception. It often results in a more bulky and less compact device. Porro prisms are generally less expensive than roof prisms.
• Advantages: Typically offers a brighter image and a wider field of view.
• Disadvantages: Bulkier design.

2. Roof Prisms:

• Schmidt-Pechan Prism: A common roof prism type used in many compact binoculars and monoculars. It features a compact design and a reflective coating that helps with light transmission. Schmidt-Pechan prisms are usually less expensive than high-end roof prisms.
• Abbe-Koenig Prism: Another roof prism type that is longer and often used in higher-end models. It provides high light transmission and image brightness, similar to the Schmidt-Pechan but with a different design.
• Advantages: More compact and streamlined design.
• Disadvantages: Typically more expensive due to complexity and manufacturing costs.

3. BAK4 Prism:

• BAK4 Prism: A high-quality glass used in roof prisms (Schmidt-Pechan and Abbe-Koenig) known for excellent light transmission, brightness, and minimal image distortion. BAK4 prisms are generally more expensive due to the quality of the glass.
• Advantages: Provides superior image quality with higher brightness and less distortion.
• Disadvantages: More expensive due to the advanced glass technology.

4. Porro II Prisms:

• Porro II Prism: An improved version of the classic Porro prism, offering better alignment and compactness while maintaining the Porro prism's characteristics.

Summary of Expensiveness:

• More Expensive: BAK4 prisms and Abbe-Koenig roof prisms are typically more expensive due to their high-quality glass and advanced optical performance.
• Less Expensive: Schmidt-Pechan roof prisms and classic Porro prisms tend to be less expensive, with Schmidt-Pechan being a more budget-friendly option for roof prisms.

In general, the choice of prism type affects both the cost and the design of the optical device, with higher-quality prisms offering better performance at a higher price.