In 1840 he developed the calotype;an early photographic process that improved on the daguerreotype, it involved the use of a photographic negative, from which multiple prints could be made.

• 1840年他开发卡罗式照相法，这是一种改良达盖尔式照相法的早期照相方法，它使用一种摄影负像，由此可以复印多份照片。