A high tone image is saved in a versatile image file format to enhance usability. There are provided an imaging unit that images an original image having a predetermined dynamic range, which is a ratio between minimum luminance and maximum luminance; a synthesized image generating part that generates a synthesized image data that is higher in tone than a tone width of the original image by synthesizing a plurality of original images imaged under different imaging conditions at the same observation position; a display unit that displays the images imaged by the imaging unit; a tone conversion part that converts the synthesized image data generated by the synthesized image generating part to low tone image data having a tone width capable of being displayed on the display unit; and a tone data saving part that generates a high tone data-attached display file including a high tone image region for saving the synthesized image data serving as a basis as an image file for saving the low tone image data.