PROBLEM TO BE SOLVED: To provide an endoscope system, an endoscope system processor device, an operation method for the endoscope system and an operation method for the endoscope system processor device, capable of displaying a warning when the dirt, such as colored mucus, adhering to an observation target needs to be removed.SOLUTION: The endoscope system comprises: an image signal acquisition unit for acquiring a first image signal in a first wavelength range where the amount of light absorption changes according to the concentration of a yellow pigment, a second image signal in a second wavelength range where the amount of light absorption changes according to the blood volume of an observation target, and a third image signal in a third wavelength range where a change in the amount of light absorption according to the blood volume is smaller than the second wavelength range； a signal ratio calculation unit for calculating a first signal ratio on the basis of the first and second image signals and calculating a second signal ratio on the basis of the second and third image signals, per each pixel； and a warning notification unit for calculating a threshold value for comparison with the first signal ratio according to the second signal ratio and generating a warning notification signal on the basis of the result of the comparison.【課題】観察対象に有色の粘液等の汚れを洗浄する必要がある場合に警告を表示することができる内視鏡システム、内視鏡システム用プロセッサ装置、内視鏡システムの作動方法、内視鏡システム用プロセッサ装置の作動方法を提供する。【解決手段】黄色色素の濃度に応じて吸光量が変化する第１波長範囲の第１画像信号と、観察対象の血液量に応じて吸光量が変化する第２波長範囲の第２画像信号と、第１波長範囲よりも黄色色素の濃度による吸光量の変化が小さく、かつ、第２波長範囲よりも血液量による吸光量の変化が小さい第３波長範囲の第３画像信号と、を取得する画像信号取得部と、第１，第２画像信号に基づいて第１信号比を、第２，第３画像信号に基づいて第２信号比を画素毎に算出する信号比算出部と、第１信号比と比較する閾値を第２信号比に応じて算出し、その比較結果に基づいて警告報知信号を生成する警告報知部と、を備える。【選択図】図８
