Sensitometry

Abstract: A method is described for the quantitative volumetric analysis of the mammographic density (VBD) from digitized screen-film mammograms. The method is based on initial calibration of the imaging system with a tissue-equivalent plastic device and the subsequent correction for variations in exposure factors and film processing characteristics through images of an aluminum step wedge placed adjacent to the breast during imaging. From information about the compressed breast thickness and technique factors used for taking the mammogram as well as the information from the calibration device, VBD is calculated. First, optical sensitometry is used to convert images to Log relative exposure. Second, the images are corrected for x-ray field inhomogeneity using a spherical section PMMA phantom image. The effectiveness of using the aluminum step wedge in tracking down the variations in exposure factors and film processing was tested by taking test images of the calibration device, aluminum step wedge and known density phantoms at various exposure conditions and also at different times over one year. Results obtained on known density phantoms show that VBD can be estimated to within 5% accuracy from the actual value. A first order thickness correction is employed to correct for inaccuracy in the compression thickness indicator of the mammography units. Clinical studies are ongoing to evaluate whether VBD can be a better indicator for breast cancer risk.

Abstract: The photographic process the nature of light photographic light sources the geometry of image formation the photometry of image formation lens aberrations the camera lens types of camera the elements of the camera camera movements optical filters and attachments the sensitive material spectral sensitivity of photographic materials principles of colour photography sensitometry the reproduction of colour developers and development processing following development film speed camera exposure determination photographic papers printing and enlarging after-treatment and archival aspects of the processed image the chemistry of colour image formation evaluation of the photographic image faults in negatives and prints.

Abstract: Aesthetics animation biographies cameras (75 discussed alphabetically) chemicals - photographic chronology of photographic inventions colour computer craftsmanship densitometry developers electronic still photography emulsions enlargers exposure filters high-speed photography history of photography image motion lamps lenses light motion picture non-silver process optics organizations photographic chemistry photographic effects photographic fields photographic manufacturing photomacrography photomicrography photometry post-processing presentation processing projection sensitized materials sensitometry sound special effects viewfinder vision visual communication visual perception xerography.

Abstract: Sensitometric information is stored with a consumable print medium having a predetermined sensitometry by compressing the sensitometric information as a set of spline coefficients for use with a printer adapted to decode the set of spline coefficients to construct a sensitometric curve. A set of spline coefficients is generated, spline coefficients are encoded, and the encoded spline coefficients are stored in a manner which is accessible to a printing device adapted to make use of the media sensitometry data for purposes of device calibration. The coefficient-generating step comprises fitting a spline curve to the sensitometry data. The spline curve may be monotonic cubic. The encoding step may include encoding a difference signal representing a difference between input values for a set of sequential spline knots. The encoding step may also include encoding a difference signal representing a difference between the output values of the sensitometry curve and output values of a reference sensitometry curve for each of a set of sequential spline knots. The difference signal may be encoded by quantizing the difference signal into a set of discrete bins.