1. A method for checking a specified security feature of a value document which is present in a specified security-feature region of the value document wherein: there are captured pixel data which describe, spatially resolved with a specified optical spatial resolution, an optical image at least of the security-feature region of the value document; there are captured ultrasound data which describe an ultrasonic property of the value document at least in the security-feature region, spatially resolved with a specified ultrasonic spatial resolution, the ultrasonic spatial resolution being lower than the optical spatial resolution; from the pixel data there are established first reduced-resolution pixel data for reduced-resolution pixels of a first reduced-resolution image which describe a reduced-resolution optical image at least of the security-feature region of the value document, whose optical spatial resolution corresponds to the ultrasonic spatial resolution, so that locations respectively associated with the ultrasound data have associated therewith first reduced-resolution pixel data; and it is at least checked to what extent the first reduced-resolution pixel data and the ultrasound data correspond to each other.