Carte de visite albumen portrait of Sir David Brewster (1781–1868), photographed by McLean & Co., London. The seated portrait shows Brewster in later life wearing formal dress, the image mounted on a standard CDV card with printed studio credit and manuscript identification. Brewster was one of the most influential nineteenth-century scientists connected with the early history of photography and optical science. Sir David Brewster was a Scottish physicist, mathematician, and inventor whose work fundamentally shaped the scientific understanding of light and vision. He conducted pioneering studies in optics and polarization, and in 1815 discovered the principle now known as Brewster’s Angle, describing the polarization of reflected light. Brewster invented the kaleidoscope in 1816, a device that became one of the most popular optical amusements of the nineteenth century and demonstrated his deep interest in visual perception. He later became a central figure in Victorian scientific life, serving as Principal of the University of St Andrews and later the University of Edinburgh, and was knighted in 1832 for his scientific achievements. Brewster played a crucial role in the early development of photography. Among the earliest scientific advocates of the daguerreotype process in Britain, he recognized photography’s importance almost immediately after its public announcement in 1839. He corresponded with leading photographic pioneers and promoted the new medium through scientific publications and public lectures. Brewster also made important improvements in optical lenses used for cameras and microscopes, helping refine photographic clarity during the formative years of the medium. He is particularly remembered as the inventor of the lenticular stereoscope in 1849, a compact improvement on earlier stereoscopic viewers. Brewster’s design made stereoscopic photography practical for widespread use and led directly to the enormous popularity of stereoviews in the mid-nineteenth century. Through his work, stereoscopic photography became one of the dominant visual entertainments of the Victorian era. The reverse bears the printed imprint of Templeton Lucas & Whyte Tuck as licensees of Pouncy’s patent photographic process, along with manuscript identification. Brewster remains one of the most significant scientific figures connected with the birth and popularization of photography and stereoscopic imagery.