Control apparatus that performs focusing by imaging-plane phase difference AF, image capturing apparatus, control method, and non-transitory computer-readable storage medium

A control apparatus comprising:

• at least one processor;
• and
• a memory including instructions that, when executed by the at least one processor, cause the at least one processor to operate as:
• an acquirer configured to acquire a first signal and a second signal that correspond to light beams passing through different pupil regions of an image capturing optical system,
• a calculator configured to perform a plurality of filtering processes with different bands for the first signal and the second signal to calculate a plurality of defocus amounts and reliabilities based on the first signals and the second signals where the respective filtering processes have been performed, and
• a determiner configured to determine a defocus amount used for focusing from among the plurality of defocus amounts based on a difference between the plurality of defocus amounts and at least one of the plurality of reliabilities,
• wherein the plurality of filtering processes include:
• a first filtering process for extracting the first and second signals with a first frequency band, and
• a second filtering process for extracting the first and second signals with a second frequency band higher than the first frequency band,
• wherein the calculator is configured to calculate, as the plurality of defocus amounts and reliabilities:
• a first defocus amount and a first reliability based on the first and second signals where the first filtering process has been performed, and
• a second defocus amount and a second reliability based on the first and second signals where the second filtering process has been performed, and
• wherein when the difference between the first defocus amount and the second defocus amount is greater than a first threshold value, the calculator is configured to determine the first defocus amount as the defocus amount used for the focusing.