Weston Model 627 Leicameter (Loupe). USA manufacture 1933       Return to Early Years

The metal correction / adjustment table on the side of the Model 627 Leicameter. 

There are two tables that work independently of each other. The upper one shows corrections for different film types / speeds (in degrees Scheiner). The reference film on the meter is Super Panchromatic X with a rating of 23 deg. For different films (mainly slower), the exposure correction required is listed below the film speed. So, for a film of, say 20 degrees, the exposure would need to be doubled (+1 stop). So the aperture of f6.3 could be opened up to f4.5 or the shutter speed of, say 1/200th sec., could be set to 1/100th.

The lower table shows the necessary adjustment to be made if an aperture other than f6.3 is to be used. The multiplication factor for each aperture is listed. So if the aperture was stopped down to say f12.5, then the shutter speed would need to lengthen by two stops. The exposure time would be quadrupled.