Do you know the differences between BAK4 and BK7 in JAXY binoculars?
1,**Refractive Index**: BAK4 has a higher refractive index (approximately 1.60), which helps to better control the refraction of light, reduce optical distortion, and provide higher resolution and clarity. In contrast, BK7 has a lower refractive index (approximately 1.50), which may result in the light at the edge of the field of view not being fully reflected, thus appearing darker in edge imaging.
2,**Optical Performance**: BAK4 typically offers better optical performance because it can achieve total internal reflection, reduce light loss, and enhance the brightness and contrast of the image. While BK7 has a similar imaging effect in the central field of view as BAK4, it may be slightly insufficient in the peripheral field of view.
3,**Cost**: The manufacturing cost of BAK4 is usually higher than that of BK7 because it requires more advanced technology and stricter quality control. Therefore, BAK4 is often used in high-end telescopes, while BK7 is commonly used in mid-to-low-end products.
4,**Stability**: BAK4 has better thermal and mechanical stability, which allows it to maintain good optical performance under various temperature and environmental conditions. The performance of BK7 may decline under extreme conditions.
5,**Usage**: BAK4 prisms are typically used in high-end telescopes, while BK7 prisms are more often used in mid-to-low-end jaxy telescopes. Some low-end telescopes may use BK7 prisms to reduce costs.
6,**Identification Method**: The type of prism can be identified by observing the exit pupil spot of the telescope. If the exit pupil spot is a clear and bright circle, it is likely a BAK4 prism; if the exit pupil spot is blurred around the edges, it may be a BK7 prism.
7,**Commercial Promotion**: Some merchants in the binoculars market may over-promote the use of BAK4 prisms, but in reality, the quality of the prism is not solely determined by the material. It is also related to production processes, coating technology, and other factors.
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