The photography Series
They are often denoted with a code of the format nR, where the number n represents the length of the shorter edge in inches. In the normal series, the long edge is the length of the short edge plus 2 inches (10inches or less) or 3 inches (11inches and above). The alternative Super series, denoted SnR, has an aspect ratio of 3:2 (or as close as possible) and thus provides a better fit for standard 135 film (35 mm) at sizes of 8 inches or above.
In Japan, the same print sizes (and several additional ones) are known by different names. The Japanese L is equivalent to 3R, while 2L—twice the size—matches 5R. KG represents the size of a traditional 4inch×6inch (4R) Japanese postcard (hagaki). The nP or cut (kiri) series are defined in reference to a full page size (zenshi) of 457×560 mm, with smaller numbers (fewer cuts) indicating larger sizes.
Unlike ISO 216 paper sizes, the aspect ratios of photographic prints vary, so exact scaling of prints is not always possible. However, there are some logical correspondences between the sizes, noted below when applicable.
Many of the standard sizes are the same as sheet film formats, and are appropriate for making contact sheets from these films.