1 April 1976 Distinguishable Density Levels in Image Recording of Earth Resources Satellite Data
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Abstract
The Earth Resources Technology Satellite (ERTS, now called LANDSAT) system produces scanned images of the earth, with exposed film presented to the user in pictorial form for interpretation and analysis. Specifications for this output film include MTF requirements, development method requirements, geometric tolerance and the number of DDLs (distinguishable density levels). With regard to the DDLs, the specification requires a minimum of 64 levels of gray at the given resolution, while providing a minimum density range of 2.0. This investigation was conducted both theoretically and experimentally to determine the realizability of this goal with high-resolution photographic film as a storage medium. Assuming, first, that Selwyn's Law is valid for the range of apertures and films in this specific investigation, granularity was calculated as a function of density. A procedure was established by which films can be selected for this task. Several experiments were then performed to evaluate the practicality of these calculations. The results, which were in general agreement, indicated difficulty in achieving the DDL goal with the film selected.
Steven Scott Beiser, Steven Scott Beiser, } "Distinguishable Density Levels in Image Recording of Earth Resources Satellite Data," Optical Engineering 15(2), 152124 (1 April 1976). https://doi.org/10.1117/12.7971931 . Submission:
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