An Electronic Method of Development Control.

A new means of development control is described. Developed by J. F. Crosfield, of London, England this method has been embodied into a machine called the Gammatron. The means of control depends upon density measurements of the photographic material during development. When the density difference of two control patches reaches a predetermined value, development is automatically stopped by means of an electronic circuit. Degree of development thus becomes independent of temperature, developed activity or emulsion contrast.