Uniform Scale
From Camerapedia.org
The Uniform Scale (or US) is an old way to give the aperture settings of a lens. The following table gives the correspondence between regular f-stops and US stops:
| US stop | F-stop |
| 1 | 4 |
| 2 | 5.6 |
| 4 | 8 |
| 8 | 11 |
| 16 | 16 |
| 32 | 22 |
| 64 | 32 |
| 128 | 45 |
| 256 | 64 |
The Uniform Scale was introduced in the 1890s.[1] It was still used by some unscrupulous manufacturers in the 1950s, to make the lenses seem wider than they actually were: for example a lens marked as "US 3.5" has about f/8 maximal aperture. (See the Koniken for an example.)
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