A banquet photo usually refers to a very large-format group portrait, most commonly associated with the late 1800s through about the 1960s. The name comes from banquet cameras, which were designed to photograph large groups in spaces like banquet halls.

Traditionally, these images were made with very wide large-format cameras—often around 12x20 inches, though other panoramic formats such as 5x12, 7x17, 8x20, and 4x10 were also used. Wide-angle coverage helped fit an entire group into one image, and some banquet cameras exposed the film by rotating during the exposure to sweep across the scene.

So, in practice, a banquet photo is not just any group shot: it usually implies a large-format, wide group portrait made in the style of those historic banquet cameras. The defining traits are the very large negative, panoramic or extra-wide framing, and the ability to capture a large crowd with high detail in a single image.