1. Field of the Invention
The present invention relates to image pickup apparatuses, control methods therefor, and computer programs, and, more particularly, to an image pickup apparatus capable of detecting blur caused by the movement of a subject and preventing a blurred image from being captured, a control method therefor, and a computer program.
2. Description of the Related Art
Image pickup apparatuses such as digital cameras sometimes provide blurred photographs. Currently, various functions of preventing blurred photographs from being captured are implemented in cameras. For example, there is a function of displaying a “blur warning icon” on the display of a camera when an image capturing mode in which image capturing is performed at a shutter speed slower than a predetermined speed is set. This function is used to notify a user (photographer) that there is a possibility that blur caused by a camera shake will occur at a slow shutter speed.
Furthermore, some cameras include a gyro sensor, and have a function of causing the gyro sensor to detect the movement of a camera body held by a user (photographer) and displaying a “blur warning icon” on the display of the camera on the basis of the detection result. Thus, many techniques for detecting blur caused by the movement of a camera body and outputting a warning on the basis of the detection result have already been developed and are now being used.
However, there are two main factors responsible for the occurrence of blur in a photograph captured by a camera, that is, the above-described camera shake caused by the movement of a camera and subject shake. The camera shake occurs due to the movement of a camera body during exposure. The subject shake occurs due to the movement of a subject during exposure. Many techniques for detecting the camera shake that occurs due to the movement of a camera body and outputting a warning on the basis of the detection result have already been proposed.
On the other hand, a technique for detecting the subject shake that occurs due to the movement of a subject and outputting a warning for a user (photographer) on the basis of the detection result has not been disclosed. As a similar technique, for example, Japanese Unexamined Patent Application Publication No. 2003-323621 discloses a technique for detecting whether a person set as a subject goes out of an image capturing field and outputting a warning on the basis of the detection result. In addition, Japanese Unexamined Patent Application Publication No. 2005-20196 discloses a technique for analyzing captured images, extracting an image in which face images are overlapped or a face image is cut, and deleting the extracted image as an error photograph.
However, the above-described known techniques do not detect subject movement and warn a user of the occurrence of blur on the basis of the detection result.