Analog Roots

As a photographic practice, sharpening has its roots in the analog world, as the sidebar above indicates. However, the analog unsharp masking technique described therein offered only two controls.

• The distance between the two negatives (the thickness of the glass) controlled the width of the sharpening halo.

• The exposure time controlled the strength of the contrast boost.

The limited control and uncertain results prevented unsharp masking from becoming a mainstream practice in analog photography. But it did see some use in sharpening analog color separations for offset printing, often by making a blurred duplicate of the continuous-tone separation, then printing it together with the sharp version as a contact print, after which the separation was screened.

Sharpening for continuous-tone photographic prints was something of a luxury, but when the continuous-tone original was turned into cyan, magenta, yellow, and black dots of ink, some of the original sharpness was lost. So sharpening became, and remains to this day, a standard operation in prepress. When the drum scanner replaced the stat camera, digital sharpening became the norm.