1. An image capturing device comprising: an image capturing portion which photographs an optical image and converts the optical image into image information; a determination portion for deciding whether or not an image represented by image information obtained by photographing by the image capturing portion includes a predetermined pattern; a processing portion for performing a predetermined process in a case where a determination that the image includes the predetermined pattern is made by the determination portion; and a prohibiting portion which prohibits the determination by the determination portion in any case other than a case where photographing of an optical image is performed in at least one of a particular photographing mode and a particular image capturing condition suitable for photographing a subject corresponding to the predetermined pattern.