An image pickup system, comprising: a processing circuit (22, 23) configured to generate a first video signal having a first dynamic range from a pixel signal generated by an image pickup unit being configured to capture a subject to obtain the pixel signal, and configured to simultaneously generate, from the pixel signal, a second video signal having a second dynamic range which is correlated with the first dynamic range, and a viewfinder configured to display the first video signal generated by the processing circuit and a graphical user interface operable by a user to select a relative range indicating a correspondence between the first and second dynamic ranges, wherein: the first video signal is an SDR (Standard Dynamic Range) video and the first dynamic range is a Standard Dynamic Range, the second video signal is an HDR (High Dynamic Range) video, and the second dynamic range is a High Dynamic Range, the processing circuit is configured to set a ratio between a first master gain for the pixel signal being used for generating the first video signal and a second master gain for the pixel signal being used for generating the second video signal, based on the relative range selected by a user through the graphical user interface and indicating the correspondence between the first and second dynamic ranges, the processing circuit is configured to generate the first video signal having the first dynamic range from a signal obtained by carrying out gamma signal processing on the pixel signal. a processing circuit (22, 23) configured to generate a first video signal having a first dynamic range from a pixel signal generated by an image pickup unit being configured to capture a subject to obtain the pixel signal, and configured to simultaneously generate, from the pixel signal, a second video signal having a second dynamic range which is correlated with the first dynamic range, and a viewfinder configured to display the first video signal generated by the processing circuit and a graphical user interface operable by a user to select a relative range indicating a correspondence between the first and second dynamic ranges, wherein: the first video signal is an SDR (Standard Dynamic Range) video and the first dynamic range is a Standard Dynamic Range, the second video signal is an HDR (High Dynamic Range) video, and the second dynamic range is a High Dynamic Range, the processing circuit is configured to set a ratio between a first master gain for the pixel signal being used for generating the first video signal and a second master gain for the pixel signal being used for generating the second video signal, based on the relative range selected by a user through the graphical user interface and indicating the correspondence between the first and second dynamic ranges, the processing circuit is configured to generate the first video signal having the first dynamic range from a signal obtained by carrying out gamma signal processing on the pixel signal. the first video signal is an SDR (Standard Dynamic Range) video and the first dynamic range is a Standard Dynamic Range, the second video signal is an HDR (High Dynamic Range) video, and the second dynamic range is a High Dynamic Range, the processing circuit is configured to set a ratio between a first master gain for the pixel signal being used for generating the first video signal and a second master gain for the pixel signal being used for generating the second video signal, based on the relative range selected by a user through the graphical user interface and indicating the correspondence between the first and second dynamic ranges, the processing circuit is configured to generate the first video signal having the first dynamic range from a signal obtained by carrying out gamma signal processing on the pixel signal.