Chapter One: Comments from the lens design team.
1The dual challenge of achieving high performance within a compact body. The solution: Fixed-type lens.
- The X100 was originally conceived as a slim and compact camera for users to take with them wherever they go. When we first began considering the lens design, we examined the many possibilities from a variety of perspectives, for example, the aperture value and lens size in the case of a zoom lens and lens-body combinations in the case of an interchangeable lens system. As a result, we determined that a non-collapsible, single focal length lens was the ideal choice to meet our two goals of achieving the product concept and delivering the high level of quality demanded by professional users.
- Regarding the focal length, we considered the 135 equivalent of 24mm, 28mm, 35mm and 50mm. For each length, we evaluated the relationship between the F value and lens size, capability to satisfy user expectations, and the breadth of their application. We selected the 35mm lens as the best match for the camera concept.
2Road to the F2 aperture value.
- Designing an F1.6 or F1.8 lens is not so difficult; however, in the case of a digital camera, even if an aperture larger than F2 is used, the light receiving elements on the sensor cannot effectively use the brighter portion of the incoming light because of low incident light gathering efficiency.
- Also by choosing an aperture of F2, it is possible to achieve a higher MTF* level when the aperture is closed to F4, F5.6, F8, etc. In most photographic situations, we envisage that users will often use an aperture that is 1 to 2 stops higher than F2. Therefore, in designing the lens, we put a priority on capturing superior quality photos with exceptional expression of detail in the aperture range of F4 to F5.6.
*MTF: Modulation Transfer Function is an index of the image formation performance of the lens. The value indicates the ability to reproduce contrast over a range of spatial frequencies.
3The double-sided aspheric lens combined with high refractive index glass, results in optimum performance.
- The use of an aspheric lens increases the freedom in lens design; however, it does not necessarily lead to the development of a good lens. For the X100, spherical lens elements are used as much as possible, and one double-sided aspheric lens made by a glass moulding process has been adopted as the most effective element for delivering maximum performance.
- The X100 lens delivers performance in a compact body, and also boasts excellent results. The shape of the aspheric lens not only provides performance but also ease of manufacturing. As the other lens elements are spherical, a high level of design performance can be achieved when they are actually assembled in the product.
- High-refractive-index glass is used for all 4 convex lens elements. This is necessary to correct image field curvature and achieve optimum image quality.
45.6mm back focus.
- In the case of the X100, the lens back focus, (the distance between the rear lens element and the sensor), is remarkably only 5.6mm. Incorporating the large-diameter rear lens element in the body and shaving tenths of millimeters from the lens elements and their integration, has also allowed us to retain a very slim and compact design.
- The sensor has been specially customised just for this lens. Unlike film, the sensors of most digital cameras require incoming light to strike the sensor surface at an angle that is as perpendicular to the sensor surface as possible. Because this is difficult to achieve with a slim lens, the positioning of the microlens on the sensor of the X100 has been customised to allow the capture of light rays with up to a 20° angle of incidence. Without this sensor customisation, it would be necessary to lengthen the size of the lens by 10mm.
5Large-diameter internal lens structure – unnoticeable from the front.
- Exploiting the benefits of a fixed lens, the rear lens element is larger than the front lens element. By giving it a diameter of 27mm, which is about the same as the sensor's diagonal dimension of 28.4mm, ample light volume can be received in the edge areas of the sensor.
69-blade aperture diaphragm and a high-performance lens shutter system.
- In order to capture images with a beautiful "bokeh" effect with the background softly out of focus, a 9-blade aperture diaphragm has been adopted for the X100.
- The 4-blade shutter achieves a maximum shutter speed of 1/4000s. Because the X100 uses a lens shutter system, the camera is capable of high-speed flash synchronisation.