Patent ID: 7916206

Claim:
A focus detection apparatus configured to generate, based on an output from a plurality of pixels of a photoelectric converting element which photoelectrically converts an object image formed by an optical system, focusing information representing a focus state of the optical system, the focus detection apparatus comprising: an information generating section configured to generate luminance information of each of the plurality of pixels based on the output from the plurality of pixels of the photoelectric converting element; a setting section configured to set a luminance value or a luminance range of values based on the luminance information of at least one of the plurality of pixels; and an information outputting section configured to receive the luminance information from the information generating section, configured to count a number of at least one of the plurality of pixels whose luminance information is higher or lower than the luminance value or the luminance range of values set by the setting section, and configured to output count information as the focusing information, wherein the setting section newly calculates and sets the luminance value or the luminance range of values when a change in the counted number is greater than a predetermined amount in a state of completion of a focusing operation by the optical system.