An image processor includes a luminance signal processor configured to
execute an amplification by utilizing a gain set by a plurality of gain
step-sizes including a first gain step-size and a second gain step-size
less than the first gain step-size, to an image signal component which is
equal to or less than a fixed luminance level in an image signal. The
control circuit is configured to control increase and decrease of the
gain utilized by the amplification and the gain step-sizes based on a
ratio that a luminance level of the image signal component is equal to or
less than the reference detection level, a ratio that the luminance level
of the image signal component is equal to or less than a first detection
level greater than the reference detection level, and a ratio that
luminance level of the image signal component is equal to or less than a
second detection level less than the reference detection level.