ABSTRACT
This chapter examines the image noise and sharpness, and the ways in which these limit the usefulness of images and imaging systems as carriers of information. Image noise is essentially the unwanted fluctuations of light intensity over the area of the image. The sensation of non-uniformity in the image produced in the consciousness of the observer when the image is viewed is termed graininess. Methods for quantifying image noise are presented in the following sections in terms of the photographic imaging process, where noise fluctuations are measured in density units. The noise field is scanned and sampled using a long thin slit to produce a one-dimensional trace for analysis. For each frequency the image modulation is determined from a scan of the image. The term 'sharpness' refers to the subjective impression produced by an edge image on the visual perception of an observer, produced by either film or a digital sensor.
