The front element of the 6 mm Ultra 16 lens, with the radical spherical surface highlighted in red

 

In order to achieve a high quality image even at wide open T-stops, lens designers are using new shapes for the surfaces of individual lens elements. These new shapes help eliminate optical aberrations and distortions, while keeping the lens' size and weight down. One of these shapes is the radical spherical lens surface. These surfaces have a very strong curvature; some are almost half-sphere shaped. They are called 'spherical' since the curvature remains constant.

Improved precision manufacturing and new measurement techniques have made the creation and verification of these lens surfaces possible. Still, radical spherical surfaces are cutting edge technology; they are difficult to grind, tricky to polish and demand precise attention during coating. However, mastering these manufacturing techniques brings the reward of incomparable optical performance at substantially reduced weight.

Radical spherical lens surfaces are used in the ARRI/Zeiss Ultra 16 lense and in the ARRI/Zeiss Lightweight Zoom LWZ-1.