Developed to help users take better photographs, image stabilization technology has become increasingly widespread in recent years. With single-lens reflex (SLR) cameras, image stabilization systems can be installed either within the interchangeable lenses or the camera body itself. Sony's α series digital SLR cameras are equipped with image stabilization functions built into the camera body --- referred to as "SteadyShot INSIDE." With systems that rely on lens-based image stabilization, stabilization may not be supported for all lenses. A key advantage of Sony's α series digital SLR cameras is that image stabilization is not dependent on the lens. In other words, camera-body based stabilization ensures stabilization for any lens (from wide-angle to telephoto) including previously purchased α lenses.
Sensor-shift Image Stabilization
In digital SLR cameras, image stabilization is based on the sensor-shift method or the lens-shift method (Figure 1). α series cameras use the sensor-shift method which stabilizes the image by moving the image sensor inside the camera body. Because the amount of drive required to correct camera shake varies according to the lens, focal-distance data from the lens is required to control the adjustment. With the α series, data is exchanged via the contact points between the body and the lens, enabling the stabilization process to be controlled within the body.
- Sensor-shift Method
- Image stabilization is achieved by shifting the image sensor in the direction required to cancel out camera-shake and eliminate the resulting blurring of the image on the sensor.
- Lens-shift Method
- Image stabilization is achieved by shifting a corrective lens in the direction required to cancel out movement on the optical axis resulting from camera shake.
Image Stabilization System
Figure 2 is a block diagram of the image stabilization system. The α series image stabilization system (SteadyShot INSIDE) is controlled by a microcomputer, which repeatedly carries out the digital servo processes (described in 1. through 3. below) at a specific frequency.
Angular velocity signals from the shake detector (Gyroscope sensor) are amplified in an analog signal processing circuit and converted into digital signals by the control microcomputer. The resulting angular velocity signal input is then converted into shake angle data through signal processing. Information about the focal length of the interchangeable lens is then used to convert the shake angle into shake distances on the image sensor.
Positioning signals from the position detector (a magnet that moves in unison with the image sensor and an opposing hall sensor) are amplified in an analog signal processing circuit and converted into digital signals by the control microcomputer.
The amount of image sensor movement required is calculated from the amount of shake and the current position. The system then drives the actuators accordingly.
