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Showing papers on "Dark-frame subtraction published in 1985"


01 Jan 1985
TL;DR: The performance of the method is assessed in terms of gain in signal-to-noise ratio (S/N-ratio) and by visual inspection.
Abstract: In this paper a digital image processing method for removing noise from still and moving grey-value pictures is presented and its performance is investigated. The method consists of replacing a particular noisy pixel by a weighted average of pixels in some standard neighborhood of the pixel. In case of a single still picture the neighborhood has two spatial dimensions, while for sequences of pictures, neighborhoods with an additional third (time) dimension are used. With the aid of edge detectors in various directions a king of contour plot is constructed which indicates to what extent a pixel of the standard neighborhood belongs to the same region as the pixel being restored. This contour plot is converted into a set of weight coefficients of a transversal filter. The performance of the method is assessed in terms of gain in signal-to-noise ratio (S/N-ratio) and by visual inspection.

4 citations


Journal ArticleDOI
TL;DR: Noise measurements are presented for a medium speed screen-film combination and also for a low noise alpha 16-Kodak Industrex C system and the effect of grain mottle and film blur on noise transfer through the multiple print process employed in subtraction radiography is demonstrated.
Abstract: The transfer of noise through the stages of a screen-film subtraction process was investigated. In particular the effect of measuring aperture size and film density on the measured noise granularity was studied. The relative contributions of quantum noise and film grain noise were found to depend on both aperture and density. Noise measurements are presented for a medium speed screen-film combination and also for a low noise alpha 16-Kodak Industrex C system. The effect of grain mottle and film blur on noise transfer through the multiple print process employed in subtraction radiography is demonstrated.

3 citations


Proceedings ArticleDOI
11 Jul 1985
TL;DR: In this paper, a point transformation of signal dependent noise, such as film-grain, to signal independent noise for digitized color images is proposed, which is an extension of a technique, developed by others, for digitizing monochrome (black-and-white) images.
Abstract: Developed herein is a point transformation of signal-dependent noise, such as film-grain, to signal-independent noise for digitized color images. The idea is an extension of a technique, developed by others, for digitized monochrome (black-and-white) images.