text: A scholar working in this dynasty established the principles governing the camera obscura to describe the function of the human eye.
full_question: A scholar working in this dynasty established the principles governing the camera obscura to describe the function of the human eye. This dynasty funded the construction of the first paper mill. During the rule of this dynasty, three brothers collectively known as the Banu Musa wrote the Book of Ingenious Devices while working at the House of Wisdom. The Barmakid family advised several rulers of this dynasty, including Harun Al-Rashid. For 10 points, name this third Islamic caliphate that established a capital at Baghdad and that succeeded the Umayyads.
first_sentence: A scholar working in this dynasty established the principles governing the camera obscura to describe the function of the human eye.