1. An image capturing apparatus comprising: an imaging unit that has an image sensor in which reference band pixels and additional band pixels are arranged and that is configured to capture an object image by the image sensor receiving incident light from an object, the reference band pixels consisting of R band pixels, G band pixels, and B band pixels having spectral sensitivity peak wavelengths in R, G, and B bands, respectively, and the additional band pixels each having a spectral sensitivity peak wavelength between the spectral sensitivity peak wavelengths of a pair of adjacent bands among the R, G, and B bands; an obtaining unit configured to obtain reference band pixel values detected by the reference band pixels of the image sensor and additional band pixel values detected by the additional band pixels in the object image captured by the imaging unit; a spectral analysis unit configured to obtain a feature quantity in spectral characteristics of the incident light by analyzing the reference band pixel values and the additional band pixel values; and an image processing unit configured to perform image processing on the object image according to the feature quantity, wherein in the image sensor, the number of additional band pixels is smaller than any of the number of R band pixels, the number of G band pixels, and the number of B band pixels.