Leica format

Most of classic film cameras use small Leica format film. It is called as 'Leica format' or '35 mm film'. This is a 36 mm wide and 24 mm tall film which is used at most of SLR small-format cameras. The measures of Leica format are considered in digital photography, as digital photography tends to reach as same quality of final image. This is also a expected dimension of real size of sensor in future.
When talking about image sizes, in some cases (mostly at magnifying) we use Leica format language. At Leica, the image ratio of 1:1 means that the subject has exactly as same dimension as it physically appears on film. Thus, a 36 mm wide subject covers a full Leica format film range, and at 3:1 the subject will be three times larger on film as is original. As sensor dimension is smaller as Leica format, the ratios can be recalculated, but because of different sensor dimensions is commonly to use Leica.