SCHOTT (Mainz, Germany) has developed a version of its N-BK7 glass that offers extremely high transmission (HT) for the types of prisms used in digital theater projectors. The new N-BK7HT guarantees a minimum transmission of 99.6% at a wavelength of 400nm and a thickness of 25mm. Within the visible spectrum range of between 400 and 700nm, the absorption coefficient is three times lower than with standard N-BK7. This means less heat is generated and the risk of image errors is much lower. By expanding its prism manufacturing capabilities, SCHOTT can now produce polished or coated prisms of up to 200mm in size. With smaller dimensions, surfaces with a flatness of up to •⁄10 and quality of up to 20/10 (Scratch & Dig) can be achieved.