These high-end polarizing filters feature a more precisely specified polarizing film, and the film pieces are specially selected. After being laminated between high-quality cover glasses, an additional grinding and polishing process is performed. This ensures outstanding sharpness even with very fast, apochromatic lenses. The lamination technique provides long-term stability even in humid climates. The generation of Käsemann High Transmission (HTC) polarizing filters uses a polarizing film that offers higher light transmission while still maintaining excellent efficiency. The filter extension factor is only 2 - 3, which corresponds to approximately 1 - 1.5 stops.