Showing papers on "Tone mapping published in 1999"
24 Oct 1999
TL;DR: An approach for improving the effective dynamic range of cameras by using multiple photographs of the same scene taken with different exposure times, which enables the photographer to accurately capture scenes that contain a high dynamic range, i.e., scenes that have both very bright and very dark regions.
Abstract: This paper presents an approach for improving the effective dynamic range of cameras by using multiple photographs of the same scene taken with different exposure times. Using this method enables the photographer to accurately capture scenes that contain a high dynamic range, i.e., scenes that have both very bright and very dark regions. The approach requires an initial calibration, where the camera response function is determined. Once the response function for a camera is known, high dynamic range images can be computed easily. The high dynamic range output image consists of a weighted average of the multiply-exposed input images, and thus contains information captured by each of the input images. From a computational standpoint, the proposed algorithm is very efficient, and requires little processing time to determine a solution.
427 citations
TL;DR: The results of this study showed that it was possible to maintain the perceived lightness contrast of the images by using sigmoidal contrast enhancement functions to selectively rescale images from a source device with a full dynamic range into a destination devices with a limited dynamic range.
Abstract: In color gamut mapping of pictorial images, the lightness rendition of the mapped images plays a major role in the quality of the final image. For color gamut mapping tasks, where the goal is to produce a match to the original scene, it is important to maintain the perceived lightness contrast of the original image. Typical lightness remapping functions such as linear compression, soft compression, and hard clipping reduce the lightness contrast of the input image. Sigmoidal remapping functions were utilized to overcome the natural loss in perceived lightness contrast that results when an image from a full dynamic range device is scaled into the limited dynamic range of a destination device. These functions were tuned to the particular lightness characteristics of the images used and the selected dynamic ranges. The sigmoidal remapping functions were selected based on an empirical contrast enhancement model that was developed for the result of a psychophysical adjustment experiment. The results of this study showed that it was possible to maintain the perceived lightness contrast of the images by using sigmoidal contrast enhancement functions to selectively rescale images from a source device with a full dynamic range into a destination device with a limited dynamic range.© (1998) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
129 citations
Patent•
30 Dec 1999TL;DR: In this article, a technique for adjusting the dynamic range in an imaging system includes balancing of pure gray level processing with pure frequency processing to reduce the brightness of light regions in an image and to maintain contrast in darker regions.
Abstract: A technique for adjusting the dynamic range in an imaging system includes balancing of pure gray level processing with pure frequency processing to reduce the brightness of light regions in an image and to maintain contrast in darker regions. The technique applies unsharp masking in which a set of parameter values are used based upon smoothed pixel values for an image. The unsharp masking parameters may be substantially zero below a threshold, and increase nonlinearly above the threshold. A set of brightness control parameters are then used to adjust an output value for each pixel to a desired dynamic range. The brightness control parameters may also be nonlinear.
9 citations
24 May 1999
TL;DR: In this article, a tone scale that can improve consistency in appearance among various devices with different luminance was proposed to realize the lightness-equivalent characteristic of radiographic images, which is defined as a relative brightness of region of interest compared with the maximum luminance level of the image.
Abstract: Appearances of images are closely related with the luminance dependence of human visual characteristics. Radiographic images are displayed on the CRTs with various luminance as well as on high luminance light-boxes. We studied a tone scale that can improve consistency in appearance among various devices with different luminance. It is likely that radiologists diagnose images based on the relation between the brightness of region of interest and that of surrounding area. Lightness is defined as a relative brightness of region of interest compared with the maximum luminance level of the image. We think the lightness index can be applied for realizing the appearance matching of radiographic images. Lightness matching can be realized by displaying images with the tone scale which gets agreement of the gradients of the display tone scale, on the logarithm of output luminance vs. input data level plane, among display systems. In this paper we call it a 'lightness-equivalent' characteristic. We evaluated the appearance consistency of images displayed with the log-luminance linear tone scale, as realizing the lightness equivalent characteristic, compared with those displayed with the perceptual-linear tone scale. In evaluation the log-luminance linear tone scale gave almost the same appearance among devices with different luminance. On the other hand, the perceptual-liner tone scale gave lower visual contrast for images on the lower luminance device than the higher luminance device, which might have lead to observers perceiving as different appearances.© (1999) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
2 citations