I understand spherical aberration. I think you are overestimating the importance of it in modern binoculars. EP size is more important now because spherical aberration is largely a problem with cheaper binoculars and is not a common problem anymore with high-end binoculars that use more complex lens designs to control it. I guarantee you, NL's and SF's do not have spherical aberration because their complex eyepieces control it. As far as Leica binoculars being the best in the world, that depends on what your priorities are. If you like a large, bright FOV with highly corrected edges, and a flat field. Leica's are definitely not the best in the world. If you like warm, saturated colors, high distortion, soft edges, less brightness and a small FOV they might be the best for you. It just depends on what your priorities are in a binocular.
Yes, spherical aberration is often a noticeable problem with cheap binoculars, as the lower quality lens design in budget optics usually doesn't adequately correct for this optical aberration, resulting in blurry image edges and reduced overall sharpness, especially when looking towards the periphery of the view field.
Key points about spherical aberration in cheap binoculars:
- Cause:
Light rays hitting the edges of a spherical lens are refracted differently than those hitting the center, causing them to focus at different points, leading to a blurry image.
- Impact:
Cheap binoculars often have significant spherical aberration, making the image appear sharp in the center but blurry at the edges.
- Solution in high-end binoculars:
Higher quality binoculars use more complex lens designs, including aspherical lens elements, to minimize spherical aberration and provide a sharper image across the entire field of view.