Showing papers on "High-dynamic-range imaging published in 2002"

Photographic tone reproduction for digital images

Abstract: A classic photographic task is the mapping of the potentially high dynamic range of real world luminances to the low dynamic range of the photographic print. This tone reproduction problem is also faced by computer graphics practitioners who map digital images to a low dynamic range print or screen. The work presented in this paper leverages the time-tested techniques of photographic practice to develop a new tone reproduction operator. In particular, we use and extend the techniques developed by Ansel Adams to deal with digital images. The resulting algorithm is simple and produces good results for a wide variety of images.

Gradient domain high dynamic range compression

Abstract: We present a new method for rendering high dynamic range images on conventional displays. Our method is conceptually simple, computationally efficient, robust, and easy to use. We manipulate the gradient field of the luminance image by attenuating the magnitudes of large gradients. A new, low dynamic range image is then obtained by solving a Poisson equation on the modified gradient field. Our results demonstrate that the method is capable of drastic dynamic range compression, while preserving fine details and avoiding common artifacts, such as halos, gradient reversals, or loss of local contrast. The method is also able to significantly enhance ordinary images by bringing out detail in dark regions.

High Dynamic Range Imaging of Natural Scenes.

Abstract: The ability to capture and render high dynamic range scenes limits the quality of current consumer and professional digital cameras. The absence of a well-calibrated high dynamic range color image database of natural scenes is an impediment to developing such rendering algorithms for digital photography. This paper describes our efforts to create such a database. First, we discuss how the image dynamic range is affected by three main components in the imaging pipeline: the optics, the sensor and the color transformation. Second, we describe a calibrated, portable high dynamic range imaging system. Third, we discuss the general properties of seventy calibrated high dynamic range images of natural scenes in the database (http://pdc.stanford.edu/hdri/). We recorded the calibrated RGB values and the spectral power distribution of illumination at different locations for each scene. The scene luminance ranges span two to six orders of magnitude. Within any scene, both the absolute level and the spectral composition of the illumination vary considerably. This suggests that future high dynamic range rendering algorithms need to account jointly for local color adaptation and local illumination level.

High-dynamic-range imaging for digital still camera

Abstract: The paper presents a collection of methods and algorithms able to deal with high dynamic range of real pictures acquired by digital engines (e.g. CCD/CMOS cameras). Accurate image acquisition can be not well suited under difficult light conditions. A few techniques that overcome the usual 8 bit-depth representations by using differently exposed pictures and recovering the original radiance values are reported. This allows capturing both low and highlight details, fusing the various pictures into a singe map, thus providing a more faithful description of what the real world scene was. However in order to be viewed on a common computer monitor the map needs to be re-quantized while preserving visibility of details. The main problem comes from the fact that usually the contrast of the radiance values is far greater than that of the display device. Various related techniques are reviewed and discussed.

High-dynamic-range imaging optical detectors

Abstract: Imaging spectrometers allowing spatially resolved targets to be spectrally discriminated are valuable for remote sensing and defense applications. The drawback of such instruments is the need to quickly process very large amounts of data. In this paper we demonstrate two imaging systems which detect a dim target in a bright background, using the coherence contrast between them, generating much less data but only operating over a limited optical bandwidth. Both systems use a passband filter, a Michelson interferometer, coupling optics and a CCD camera. The first uses the interferometer in a spatial mode, by tilting one of the mirrors to create a set of line fringes on the CCD array. The visibility of these fringes is proportional to the degree of coherence. The interferogram is displayed spatially on the CCD array, as a function of the path differences. The second system uses the interferometer in a temporal mode. A coherent point target and an extended background are imaged through the interferometer onto the CCD array, and one of the interferometer's mirrors is scanned longitudinally to vary the path difference in time. In both cases the coherent target is detected over a large dynamic range down to negative signal-to-background power ratios (in dB). The paper describes an averaging technique to improve the signal-to-noise ratio and correction techniques required to extract interferograms from the images. The spatial technique developed has the advantage of using no moving parts.