2'Real-Image'¹ versus 'Reverse Galilean'².
- Optical viewfinder options can be broadly divided into two types. One is the 'Real-Image' viewfinder which was equipped in many conventional compacts and offered the advantages of compatibility with zoom shooting and the ease of making it compact. The other is the 'Reverse Galilean' type, which requires a certain degree of size, but affords superior clarity and has been the choice of medium-format cameras like FUJIFILM’s GA645 and GF670.
- After considering both options for the X100, it was decided, that more than the 'Real-Image' type, which required many optical elements such as prisms with sacrificed viewing quality, that the simple structure and excellent clarity of the 'Reverse Galilean' type would better satisfy the demands of photographers who know and enjoy the experience of shooting with a viewfinder. Having reached this decision, the next challenge was to make the viewfinder as compact as possible.
¹ 'Real-Image' approach: A convex lens is used for both the object lens and eye lens. Because the image in the finder is inverted and reversed if this configuration is used as it is, a prism or other correcting element is incorporated to show a correctly oriented image. While this approach is easily adapted to a more compact design and zoom applications, the complexity of the elements makes this approach susceptible to degradation of image quality.
² 'Reverse Galilean' approach: This configuration is a reversed arrangement of the telescope elements (combination of convex and concave elements) originally used by Galileo. The 'Reverse Galilean' configuration of a concave lens on the object side and a convex lens on the eyepiece side is well suited for wide-angle viewing. This type of viewfinder features a simple configuration and brightness with exceptional clarity.