Image reading apparatus

An image reading apparatus, comprising:

• a document tray on which a document is stacked;
• a conveyance unit configured to convey the document stacked on the document tray;
• a reader configured to read the image of the document conveyed by the conveyance unit using a sensor, the sensor comprising:
• a first light receiving element row having a plurality of light receiving elements, which receives light of a first color, arranged in a main scanning direction;
• and
• a second light receiving element row having a plurality of light receiving elements, which receives light of a second color, arranged in the malin scanning direction, wherein the first light receiving element row and the second light receiving element row are arranged in a sub-scanning direction orthogonal to the main scanning direction,
• a setting unit configured to set a resolution for reading, by the reader, an image of the document to one of a first resolution or a second resolution which is higher than the first resolution;
• and
• a determination unit configured to determine whether the document read by the reader is a chromatic document or an achromatic document based on a reading result of the reader,
• wherein the reader is configured to read, when determining whether the document is the chromatic document or the achromatic document by the determination unit, the image of the document in the second resolution regardless of the resolution set by the setting unit.