The Claude glass was sort-of like the Hipstamatic or Instagram of its day: it presented lived reality as more beautiful and already in its documented form (be it a painting or a faux-vintage photograph). Indeed, there are similarities in style between Claude Lorrain’s paintings, the images seen in the Claude glass and the effects that the faux-vintage photo filters employ.
Claude glass: late 18th century mirror carried by tourists. "The device was typically pocket-size, with convex, gray-colored glass. When viewers looked into it, the convex shape pushed more scenery into a single focal point and the color of the glass changed the tones to be more pleasing to the eye by the standards of the contemporary picturesque paintings, which had a limited color palette. The constructed image was thought to be even more beautiful than reality."
Claude glass - A Claude glass (or black mirror) is a small mirror, slightly convex in shape, with its surface tinted a dark colour. Bound up like a pocket-book or in a carrying case, Claude glasses were used by artists, travelers and connoisseurs of landscape and landscape painting. Claude glasses have the effect of abstracting the subject reflected in it from its surroundings, reducing and simplifying the colour and tonal range of scenes and scenery to give them a painterly quality.