The high-end interchangeable lenses that Cosina designs and makes have several optical elements inside the barrel. But, did you know that these optical elements are made of several different types of glass? The “optical glass” that is used for optical elements and prisms is a very homogenous and highly transparent quality of glass, and virtually the source of high picture quality. The characteristics of optical glass can be changed by adjusting the components and composition during the manufacturing process. In fact, there are over 200 types of glass categorized as optical glass. The above photograph shows some sample pieces that Cosina made from scratch. Our high-end optical products would not exist without our knowing what characteristics result from which components and compositions.
A sheet-like “bar” of optical glass is used to make optical elements. Bars come in various sizes and thicknesses, so several bars of a single type of glass have to be prepared according to the diameter and thickness of the target optical element. Moreover, these bars are marked with a number indicating the pot in which they are melted down so that they can be traced in all lens manufacturing processes, because, even with the same type of glass, optical characteristics tend to differ ever so slightly with each pot. So, it is absolutely imperative not just to mix different types of glass but also to mix the same type of glass from differing pots.
Cosina’s Obuse factory handles more than 100 types of optical glass. They are neatly and orderly stored as bars in an optical glass warehouse so that the type best suited for design concepts can be selected, given that high-end optical lenses continuously reflect the latest optical theories and environmental concerns. Owing to their extensive knowledge and experience with optical materials, the primary mission of the Obuse Factory is to make element blanks from optical glass. This includes clearing stringent requirements that ordinary optical glass cannot. In other words, we are quite adamant about the materials we stock.