Abstract: A method for assisting in focal length detection is applicable to a digital camera having the flash. The method includes the following steps. First, the flash of the digital camera is actuated and a first image is captured. Afterwards, a characteristic exposure value of the first image is calculated. A focus range comparison table is looked up according to the characteristic exposure value to obtain an initial focus position. Then, a focus procedure is performed according to the initial focus position to obtain a target focal length.

Abstract: An assisting focusing method is applicable in an image capture device having an auto focusing (AF) procedure. The AF procedure has a preset sampling interval. The assisting focusing method includes the following steps. An image for focusing is captured. A face parameter of a face block in the image for focusing is calculated. According to the face parameter, a parameter-to-focus conversion table is looked up to acquire a focusing section. According to the focusing section and a face sampling interval, the AF procedure is performed to acquire a target focus. The face sampling interval is smaller than the preset sampling interval.

Abstract: A continuous focusing method for a digital camera is described, which is applicable to determine whether the digital camera performs a focusing procedure or not when the digital camera switches from a first scene to a second scene in a live view stage. The continuous focusing method includes the following steps. A preview image of a second scene is obtained. A blur detection procedure is performed on the preview image, so as to acquire a corresponding focus value. It is determined whether the focus value exceeds a focusing threshold value or not; if not, a focusing procedure is performed; otherwise, if the focus value is greater than the focusing threshold value, the digital camera still maintains a current focusing focal length, which represents that a focusing focal length of the second scene is the same as that of the first scene.

Abstract: A fast focusing method for a digital camera is applied in an auto focusing stage for judging whether the digital camera needs to be refocused. The fast focusing method includes recording a system time after a previous focusing (defined as a first time); capturing a system time before a current focusing (defined as a second time); performing a fuzziness detection procedure to acquire a focus value when a difference obtained by subtracting the first time from the second time is greater than a focusing time threshold; setting a focusing focal length range covering a reference focal length when the focus value is between a lower limit focusing threshold and an upper limit focusing threshold; capturing images at different focusing focal lengths respectively in the focusing focal length range; calculating a contrast value of each image; calculating a target focal length from the contrast values through a quadratic curve approximation method.

Abstract: A photographic device using a focus method includes a zoom lens, an image analyzing module, a focus distance providing module and a processing module. The zoom lens is used for capturing image information of a plurality of positions. The image analyzing module is used for analyzing contrast values of the image information of the plurality of positions. The focus distance providing module is used for providing a non-equivalent and a constant focus distance interval for capturing the image information of the plurality of positions. The processing module is electrically connected with the zoom lens, the image analyzing module, and the focus distance providing module. Whereby, the photographic device acquires the image information of the plurality of positions by the non-equivalent focus distance interval, acquires a coarse focus position, and acquires an accurate focus position by the constant focus distance according to the coarse focus position.

Abstract: A method using multiple face blocks for assisting focusing is applicable in an image capture device. The assisting focusing method includes the following steps. A focusing image is captured individually at a focusing distance. The focusing image has a plurality of face blocks. The face blocks in the focusing image are detected. Clarities of the face blocks in the focusing image are calculated with the image capture device. A face focal length corresponding to the face block is calculated according to the clarity corresponding to the face block. A target focal length is obtained according to the face focal length.

Abstract: An assisting focusing method is applicable in an image capture device having an auto focusing (AF) procedure. The AF procedure has a preset sampling interval. The assisting focusing method includes the following steps. An image for focusing is captured. A face parameter of a face block in the image for focusing is calculated. According to the face parameter, a parameter-to-focus conversion table is looked up to acquire a focusing section. According to the focusing section and a face sampling interval, the AF procedure is performed to acquire a target focus. The face sampling interval is smaller than the preset sampling interval.

Abstract: A focus method and a photographic device using the method are disclosed. The photographic device comprises a zoom lens, an image analyzing module, a focus distance providing module and a processing module. The zoom lens is used for capturing image information of a plurality of positions; the image analyzing module is used for analyzing contrast values of the image information of the plurality of positions; the focus distance providing module is used for providing a non-equivalent and a constant focus distance interval for capturing the image information of the plurality of positions; and the processing module is electrically connected with the zoom lens, the image analyzing module, and the focus distance providing module. Whereby, the photographic device acquires the image information of the plurality of positions by the non-equivalent focus distance interval and acquires a coarse focus position, and acquires an accurate focus position by the constant focus distance according to the coarse focus position.

Abstract: A fast focusing method for a digital camera is applied in the digital camera to judge whether a focusing focal length of the digital camera needs to be adjusted in an auto focusing stage. The fast focusing method includes capturing a target image at a reference focal length; performing a blur detection procedure on the target image to acquire a focus value; setting a focusing focal length range covering the reference focal length when the focus value is between a lower limit focusing threshold and an upper limit focusing threshold; capturing corresponding comparison images at different focusing focal lengths respectively in the focusing focal length range; calculating a contrast value of each comparison image; and calculating the contrast values and a target focal length through a quadratic curve approximation method, and adjusting lenses of the digital camera to the set target focal length to perform shooting.

Abstract: A continuous focusing method for a digital camera is described, which is applicable to determine whether the digital camera performs a focusing procedure or not when the digital camera switches from a first scene to a second scene in a live view stage. The continuous focusing method includes the following steps. A preview image of a second scene is obtained. A blur detection procedure is performed on the preview image, so as to acquire a corresponding focus value. It is determined whether the focus value exceeds a focusing threshold value or not; if not, a focusing procedure is performed; otherwise, if the focus value is greater than the focusing threshold value, the digital camera still maintains a current focusing focal length, which represents that a focusing focal length of the second scene is the same as that of the first scene.

Abstract: A method for assisting in focal length detection is applicable to a digital camera having the flash. The method includes the following steps. First, the flash of the digital camera is actuated and a first image is captured. Afterwards, a characteristic exposure value of the first image is calculated. A focus range comparison table is looked up according to the characteristic exposure value to obtain an initial focus position. Then, a focus procedure is performed according to the initial focus position to obtain a target focal length.

Abstract: A fast focusing method for a digital camera is applied in an auto focusing stage for judging whether the digital camera needs to be refocused. The fast focusing method includes recording a system time after a previous focusing (defined as a first time); capturing a system time before a current focusing (defined as a second time); performing a fuzziness detection procedure to acquire a focus value when a difference obtained by subtracting the first time from the second time is greater than a focusing time threshold; setting a focusing focal length range covering a reference focal length when the focus value is between a lower limit focusing threshold and an upper limit focusing threshold; capturing images at different focusing focal lengths respectively in the focusing focal length range; calculating a contrast value of each image; calculating a target focal length from the contrast values through a quadratic curve approximation method.