The LogEtron.

The LogEtron, A scanning, servo-modulated light source for photographic reproduction, is the nucleus of a line of equipment capable of both automatic dodging (unsharp masking) and automatic exposure control. These two functions, performed by feedback from a pair of phototubes to the cathode-ray tube light source, independently control both relative and absolute densities of continuous or half-tone reproductions obtained in a one step exposure. The configuration of the LogEtronic, D-5 enlarger is described to illustrate the technique for introducing and sampling the light which connects object and image. The resulting D-LogE curves, for varying amounts of feedback, illustrate the nature and effect of feedback while sample reproductions depict the compression of gross contrast, permitting full tone separation via detail contrast - both terms being defined relative to dimensions of the scanning beam. Spectral requirements of the source and phototubes are described for use in black and white, and in color reproduction. The LogEtron promises to become that link in the photographic chain which can correct, in one operation, for all prior and subsequent distortions in tonal reproduction - whether continuous or half-tone.