1. An imaging apparatus, comprising: an image sensor including a plurality of pixels; a low-resolution imaging lens having a resolution lower than a pixel pitch of the image sensor, wherein the low-resolution imaging lens is configured to focus a same subject light on the image sensor on a local area basis; and signal processing circuitry configured to analyze an output signal from the image sensor and detect a defective pixel included in the image sensor, wherein: the image sensor is configured to form, based on the same subject light focused by the low-resolution imaging lens on the image sensor on the local area basis, an optical image with a resolving power lower than a pixel resolving power corresponding to a pixel density of the image sensor and accordingly acquire an image signal having lower resolution than the pixel resolving power corresponding to the pixel density of the image sensor, and output the image signal to the signal processing circuitry, and the signal processing circuitry is configured to: process the image signal by comparing pixel values of same color pixels included in a local area on the local area basis, the local area corresponding to a cluster of the plurality of pixels of the image sensor; and detect the defective pixel based on a result of the comparison.