Chapter Two: The birth of the Hybrid Viewfinder.

1The Inspiration: Reintroducing the pleasure of a high-quality viewfinder on a digital camera.

When the engineers discussed the features to incorporate into the X100, the first item that was raised after deciding that it must have an exceptional lens was a return to the fundamentals of what makes a great camera and the enjoyment of peering through a high-quality viewfinder.
In recent years, photographers commonly frame and confirm their compositions using the LCD panel on the back of digital cameras. However, the display can be hard to see in bright sunlight, and for those who have a deep familiarity with cameras, it was wondered whether such users would like to once again experience the pleasure of shooting photos through an extremely clear and sharp viewfinder.

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.

3Frame display: 'Albada' versus 'Illuminating window' approach.

In order to display the 'bright frame' – the essential frame for composing a shot in the viewfinder, there are two approaches: the Albada type which directly displays a frame etched or coated on an element in the viewfinder or the Illuminating Window approach which displays a frame that is illuminated through the illumination window. While the Albada type is a very good approach offering the advantages of simplicity and more compact size, the Illuminated Frame is a better choice and was the selection of the X100 engineers from the perspectives of parallax when shooting at short distances and the ease and beauty of viewing the frame itself.

4Viewfinder magnification '0.5x': A vital specification that cannot be compromised.

Viewfinder magnification refers to the apparent size of the subject as seen through the viewfinder compared with the size of the subject when seen with the naked eye. The smaller this magnification value, the smaller and the further away from the camera the subject appears in the viewfinder. While reduction of viewfinder magnification is one way to reduce the size of the viewfinder itself, this results in making the all-important subject tinier and harder to see, negating the enjoyment and advantage of the viewfinder’s clarity.
The viewfinder magnification of 0.5 is generally considered the easiest to see in the case of a camera equipped with a lens with a 35mm focal length (135 equivalent) – not too low and not too high. The challenge that faced our engineers was designing the optics to make the viewfinder as small as possible while maintaining this magnification ratio.

5The prism and lens: Keys to both compact design and performance.

The prism is the key to the approach adopted to achieve a compact form. In the structure of the 'illuminated window' bright frame, a flat mirror is generally used to reflect the frame illuminated from the illuminating window due to cost considerations; however, in the X100, a prism, which enables a more compact design than a mirror, is incorporated. As in the case of the GF670, the reflecting film is sandwiched between two prisms, providing a significantly higher reflection coefficient. As a result, the light path is shortened to 2/3 of a mirror system.
In addition, while the optical system of the viewfinder section consists of a simple configuration of 2 spherical lenses, the use of high-refraction-index glass contributes to both compactness and simplicity. Also, as in the case of the shooting lens, the finder lens elements are treated with Fujifilm’s proprietary Super EBC (electron beam coating), preventing ghosting even under strong backlighting conditions and delivering an exceptionally clear view.
By setting a relatively high eye point (distance between the eyepiece and the naked eye) of about 15mm, the design facilitates natural and comfortable viewing even by eyeglass wearers.