An image reading apparatus includes a projector for projecting light through a translucent film so as to produce a projected image from an original image on the film, a correction part for adjusting a quantity of the light, an image sensor for reading out an image from the projected image and outputting an analog signal indicating the read-out image, a signal conversion part for converting the analog signal into a digital signal indicating the read-out image, and a control part for measuring a peak value of digital signals supplied by the signal conversion part with respect to an effective range of the original image, and for allowing the correction part to adjust appropriately the quantity of the projected light in response to the measured peak value of the digital signals.