An image can be read during main scanning under an optimized image reading condition even if dust is attached to a document such as a photographic film or the like, or if there are scratches. A scanner irradiates visible light and infrared light from a light source, and an image of the document is separated into infrared and visible components. These components are detected for pixels of the image by an image sensor. A controller, e.g., of the scanner recognizes defective pixels based on the infrared component. Furthermore, the controller corrects a visible component level in the defective pixel based on the infrared component level of the defective pixel and a reference level obtained where there is no defect, in order to create a histogram. The controller determines image reading conditions such as, for example, an exposure amount (exposure time) for use during main scanning and an LUT gradation conversion characteristic based on this histogram.