Lantern slides are an early and historically significant form of photographic transparency, produced on glass rather than the flexible plastic base used in modern slide film, and designed for viewing by projection using a device known as a magic lantern. The term was the standard photographic description for projected transparencies throughout the latter half of the nineteenth century and the early decades of the twentieth century, predating the modern use of the word slide by many decades.
The magic lantern itself was an optical projection device that predated photography, using a lamp - originally candle or oil based, later replaced by more powerful limelight and eventually electric arc and tungsten sources - to project images painted or printed on glass slides onto a screen or wall for audiences. With the advent of photography in the mid nineteenth century, photographic images began to be produced directly onto glass using a variety of processes, including albumen, collodion, and later gelatin silver emulsions, creating photographic lantern slides that could be projected with far greater detail, realism, and tonal subtlety than hand painted slides.
Lantern slides were typically produced in a standard size of 3.25 by 4 inches, though other sizes existed, and were usually bound between two pieces of glass with a paper or card mask to protect the emulsion and define the image area. They were widely used for educational lectures, public entertainment, scientific presentations, religious instruction, and travel illustrated talks throughout the Victorian and Edwardian eras, making photography accessible to large audiences in a way that individual prints could not achieve.
The lantern slide tradition directly anticipated and influenced the later development of 35mm colour slide film and the culture of projected slide presentations that remained standard practice in both professional photography and domestic entertainment well into the latter decades of the twentieth century. Many collections of Victorian and Edwardian lantern slides survive in museums, libraries, and private collections, representing an invaluable visual record of life, travel, science, and culture from the early age of photography.