Amersham's .gel files: scaling issues

Phosphorimager plates are great for imaging radioactive gel emissions - they have a high dynamic range and linear response (Johnston et al., Electrophoresis, 11, 355 (1990)). Data values are read out by a laser scanner (a Storm 860 in our case) and stored in a .gel file, which is basically a TIFF file with a few extra private tags.