Comparison of the Gray Scale Characteristics of Analog and Video (Digital) Formatters

Abstract

The purpose of this study was to determine the relationship between optical density and image counts for video (digital) and analog formatters so that a video formatter could be adjusted to mimic the performance characteristics of an analog formatter. The relationship between optical density on film and image counts was determined for a video formatter and for four different analog formatters. All analog formatters demonstrated a similar logarithmic relationship, between optical density and counts, over the optical density range of 0–3.2. The video formatter gave the standard film density response curve for the film type, with a maximum optical density of 2.0. A gray scale map was created on a computer to permit the video formatter to simulate the performance characteristics of the analog formatter over the limited optical density range of 0–2.0. Both graphic and tabular techniques are described for the creation of such gray scale maps.