Thomas Keith trained in surgery at the University of Edinburgh. At the time he took up photography, he was in general practice in Edinburgh with his brother, George. According to his obituary, he 'was always in earnest: and whatever he found to do, he did it with all his might.' This is seen in his photography, where he worked with the waxed paper process, achieving subtle and strong effects by the exact use of chemistry. He gave up photography after 1859 due to the demands of his highly successful medical practice.