1. A camera system, comprising: an imaging optical system configured to form an optical image of a subject; an imaging component configured to convert the optical image into an image signal and to cyclically acquire images of the subject based on a photography condition; a display component having first and second display regions that allow a plurality of the images acquired by the imaging component to be displayed side by side; a condition input component with which the photography condition can be inputted; a condition adjustment component configured to adjust the photography condition to a preset first photography condition in a first cyclical period and to adjust a second photography condition inputted to the condition input component at a different timing from the timing at which the photography condition is adjusted to the first photography condition; and a display control component configured to control the display component to cyclically display at least part of a first image cyclically acquired in the first cyclical period by the imaging component under the first photography condition as a reference image in the first display region and to cyclically display at least part of a second image cyclically acquired by the imaging component at a different timing from that of the first image as a comparative image in the second display region, wherein the condition adjustment component is configured to adjust the photography condition to the first photography condition in the first cyclical period and the photography condition to the second photography condition in a second cyclical period that is the same as the first cyclical period, and wherein the display control component is arranged to continue to display the most recent reference image on the display component until a newer reference image is acquired.