What does the T* stand for on ZEISS products?
Carl Zeiss T* is a guarantee of the brilliant, high-contrast images which you will experience above all in adverse light conditions and in the twilight when you focus on your target through the binoculars and get it firmly in your sights through the riflescope.
The process was developed by Alexander Smakula some 80 years ago in the Carl Zeiss workshop in Jena, and the patent was registered in November 1935.
Alexander Smakula from Carl Zeiss Jena had at that time already discovered that when light enters or leaves a lens, a certain percentage of the light is reflected from the boundaries. Depending on the type of glass used this is usually between 4 and 8%, and depending on the number of lenses the total light lost can be more than 50%. Smakula countered this significant disadvantage by covering the surface of the lenses with extremely thin layers of special materials. In doing so he changed the transfer of air to glass, thereby reducing the reflections. This led to greatly improved light transmission. Binoculars and riflescopes with this "Transmission layer" were from that point, given the designation "T", and the improved multi-layer coating developed at the end of the ‘70s was named "T*". The process involves the vapour deposition in a high vacuum of layers of material, with each of the six or so layers adding approx. 1/10,000 mm.
Today we call this process "coating" or "anti-reflection coating". It is in common use with anyone who wears glasses or uses hunting optics. For them, Smakula's findings have led to bright, high-contrast images without distracting reflections: a feature of all sophisticated ZEISS optics that we take for granted today.
The coating is still known as the Carl Zeiss T* multi-layer coating. Behind it, however, there is no specific formula for building up the layers. Instead, it is a technology that is constantly adjusted to suit new glass materials and requirements, which varies from lens to lens.
For us, the Carl Zeiss T* multi-layer coating is a core skill, and one that we are constantly developing.