Abstract: Disclosed is a method which comprises the steps of providing a video-signal output device (4), accepting a brightness component of a video signal corresponding to a first position of a subject (1) which is imaged by the video-signal output device (4), correcting a gamma (?) value of the brightness component corresponding to the first position, accepting a brightness component of the image signal corresponding to a second position of the subject (1) which is imaged by the video-signal output device (4), correcting the gamma (?) value of the brightness component corresponding to the second position, calculating a ratio between the gamma-corrected brightness component corresponding to the first position and the gamma-corrected brightness component corresponding to the second position, and displaying the ratio.

Abstract: An improved channel detecting apparatus is provided for detecting a channel. The channel detecting apparatus comprises a channel search circuit (3). When a certain frequency is detected through a search sweep using a frequency sweep signal for a channel, the channel search circuit determines whether or not the detected frequency falls within a frequency range associated with the channel. The channel search circuit (3) comprises a controller (32). The controller can comprise a sweep stop timing circuit (320) and a sweep resume timing circuit (322). The sweep stop timing circuit (320) stops the search sweep when the output of the channel is generated in response to the search sweep using a frequency sweep signal.