Image reading apparatus and image forming apparatus having a light adjusting member

An image reading apparatus comprising:

• a reading unit reading an original document;
• a first guide member having a first surface placing the original document thereon when the reading unit reads the original document and a second surface, the second surface being the back of the first surface;
• a second guide member disposed opposite to the first surface of the first guide member;
• a plurality of document detection sensors, disposed opposite to the second surface of the first guide member, detecting a size of the original document placed on the first surface;
• a light adjusting member, disposed between the first guide member and the second guide member, adjusting permeation of light irradiated from the reading unit;
• and
• a light adjusting control unit controlling the light adjusting member,
• wherein the light adjusting control unit controls the light adjusting member such that the light adjusting member reflects the light irradiated from the document detection sensors when the document detection sensors detect the size of the original document, the light adjusting control unit controls the light adjusting member such that the light adjusting member permeates the light irradiated from the reading unit when the reading unit reads the original document.