Fujifilm Doubles Autofocusing Speed With New Image Sensor
Fujifilm Corp will release the F300EXR, a lens integrated camera whose autofocusing speed is twice as fast as that of the company's previous lens integrated cameras, in September 2010 in Japan.
The expected retail price of the camera is ¥45,000 (approx US$516). The autofocusing speed was realized by utilizing some of the pixels that are normally used for measuring distances.
Canon Inc, Nikon Corp and other single-lens reflex (SLR) camera makers and image sensor makers are developing such autofocus (AF) functions for mirrorless cameras. The fact that Fujifilm succeeded in commercializing its AF function means that other companies' new AF functions will probably be useful too.
The F300EXR basically uses phase detection autofocus, which is normally used for SLR cameras. And it uses contrast autofocus only for complementary purposes.
Phase detection autofocus estimates the distance between a camera and a subject from the difference in illuminance between physically separate two points and focuses on the subject by moving a focusing lens at once. And contrast autofocus moves a focusing lens to search for the lens' position that makes a clear image (high contrast ratio).
With contrast autofocus, it takes time to measure a contrast ratio at each position of the focusing lens and reflect it in the movement of the lens.Note 1) On the other hand, phase detection autofocus has a lower accuracy than contrast autofocus in principle because it does not check the position of a focusing lens or feed back as frequently as contrast autofocus. But, because of that, phase detection autofocus is faster than contrast autofocus.
Note 1) Panasonic Corp's mirrorless camera uses contrast autofocus, but its autofocusing speed is sometimes even faster than that of phase detection autofocus because of some improvements made to the camera such as the reduction of the weight of the focusing lens.
(Continue to the next page)