1. An information processing device comprising: a detecting unit configured to detect a motion of a subject included in an image generated by an imaging device including a plurality of phase difference detecting pixels which generate a signal arranged to perform focus determination by phase difference detection, and a plurality of image generating pixels which generate a signal arranged to generate an image; and a determining unit configured to determine thinning-out processing when reading out a signal from the imaging device, according to the detected motion of a subject.