Designed by Dr. Ludwig Bertele, the Biogon lens formulation exerts a powerful hold on the hearts of photographic fans around the world. Especially for use with the CONTAX G series, the T 21mm f2.8 was perfected by Carl Zeiss using the latest in optical technology. Although the Biogon T 21mm has an ultra-wide angle of view of 90 degrees, distortion is very low. High contrast is achieved even with the f stop wide open. The Biogon T 21mm lens combines rich gradation, clear, three-dimensional reproduction along with high color saturation. This lens responds well to a wide variety of photographic applications from artistic expression to architectural photography. The Biogon T 21mm f2.8 lens uses a supplied optical viewfinder with a cross-hair reticle to provide an accurate ultra-wide angle view.