Tabula scalata facts for kids
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Tabula scalata are pictures with two images divided into strips on different sides of a corrugated carrier. Each image can be viewed correctly from a certain angle. Most tabula scalata have the images in vertical lines so the picture seems to change from one image to another while walking past it. The top image on versions with horizontal strips could be seen via a mirror placed above the picture.
Some tabula scalata have the two pictures matched in shape and size, which practically creates a simple type of morphing effect when the viewing angle changes.
A variation, known as "triscenorama" or "tabula stritta" has three images: two on each side of perpendicular slats in front of the third picture.
The basic idea of tabula scalata and tabula stritta is somewhat similar to that of the ancient triangular periaktos theatre coulisse and that of the modern day Trivision billboard.
Terminology
The Latin term "Tabula scalata" was introduced in 1646 by Athanasius Kircher and can be roughly translated as "ladder picture".
The terminology in the English language has been somewhat diffuse: many different words have been used for the same type of corrugated pictures. "Perspective picture" and "anamorphic picture" have been common but not very precise terms; these are also used for very different pictures. Furthermore, it has been suggested that "anamorphic" should be reserved for the flat type of pictures with a distorted perspective. "Turning pictures" is more precise but less common. The term "double portrait" is not uncommon, but does not cover any tabula scalata that depict different subjects.
Use on British Pound Coin
The UK Pound Coin introduced in 2017 bears a small embossed image that changes from a "£" symbol to a "1", described by the Royal Mint as "like a hologram", it is actually a tabula scalata.
