This high-quality teleconverter extends the focal length of the Lumix S Pro 4 / 70-200mm / OIS and 2.8 / 70-200mm / OIS by a factor of 2 to an enormous 400mm. The light intensity is then F8.0 or F5.6. The converter, which is specially tailored to the lens, is dust-proof, cold-proof and splash-proof, just like the lens. The construction consists of 8 lens elements in 4 groups to best preserve the image quality.