Image capturing apparatus and method for controlling the same

A method for controlling an image capturing apparatus including an image sensor that includes a plurality of pixels, including a plurality of photoelectric conversion elements, and is capable of separately reading out signals separately by divided portions of the plurality of photoelectric conversion elements, the method comprising:

• a readout step of reading out a signal from a portion of the photoelectric conversion elements of each pixel as a first signal and reading out a sum of signals from the plurality of photoelectric conversion elements of each pixel as an image signal;
• a generation step of generating a second signal for each pixel, using the image signal and the first signal;
• and
• a calculation step of calculating a moving amount of a focus lens included in an imaging lens for achieving an in-focus state, based on a phase difference between the first signal and the second signal,
• wherein in the calculation step, the calculation is performed without using a signal from a defective line that includes a pixel that cannot generate the second signal using the image signal and the first signal.