PROBLEM TO BE SOLVED: To reduce an electric power consumption needed for light source part lighting.SOLUTION: An image reader including a light emitting element which irradiates a document with light and an image sensor which photoelectrically converts reflected light from the document sets a current applied to the light emitting element to a current value such that the forward current/relative flux ratio of the light emitting element becomes minimum (S1301), calculates a lighting time of the light emitting element such that an output level obtained by reading a reference white member by the image sensor is included in a range of a predetermined target value (S1302, S1306), and controls a light source part based upon a lighting signal indicative of the calculated current value and lighting time so as to perform an image reading operation (S1307).
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