Camera system, driver/passenger monitoring system, moving vehicle, image capturing method, and non-transitory storage medium

A camera system comprising:

• an image sensor having an image capturing plane and configured to capture an image of two persons on board a vehicle, wherein face images of the two persons are within an annular part of the image capturing plane;
• a bandpass filter;
• and
• an imaging optical system configured to have light coming from a subject passed through the bandpass filter and imaged on the image capturing plane,
• the bandpass filter having:
• a perpendicularly incident region on which a principal ray, which has passed through the imaging optical system, is incident perpendicularly;
• and
• an obliquely incident region on which a principal ray, which has passed through the imaging optical system, is incident obliquely,
• the image sensor having sensitivity to a light ray having a predetermined wavelength,
• the light ray having the predetermined wavelength being transmitted at a higher transmittance through at least a part of the obliquely incident region than through the perpendicularly incident region, wherein:
• the annular part corresponds to the part of the obliquely incident region of the bandpass filter having the highest transmittance with respect to the light ray having the predetermined wavelength.