Display device having an applied calibration using gradations and control methods thereof

A display apparatus comprising:

• a signal receiver configured to receive an image signal;
• a display configured to display an image based on the received image signal;
• and
• a controller configured to:
• identify a first calibration coefficient corresponding to a first gradation and a second calibration coefficient corresponding to a second gradation among a plurality of gradations, the second gradation being higher than the first gradation,
• identify a third calibration coefficient for calibrating a uniformity of the image based on at least one of the identified first calibration coefficient or the identified second calibration coefficient, the third calibration coefficient corresponding to a gradation of the received image signal, and
• control the display to apply, to the received image signal, the identified third calibration coefficient,
• wherein the applied third calibration coefficient comprises the first calibration coefficient identified based on the gradation of the received image signal being lower than the first gradation, and
• wherein the applied third calibration coefficient comprises the second calibration coefficient identified based on the gradation of the received image signal being higher than the second gradation.