MCI Imaging specialists have been using a number of imaging techniques to document and help understand the nature of cultural heritage materials. These techniques record variations in scale from micro to macro, two- and three-dimensions, light interactions beyond human vision, and so open up new ways of seeing.
High Dynamic Range Imaging (HDRI) is a computational imaging method that uses a series of images to create a single image that more accurately represents the wide dynamic range present. By processing several images representing a wide range of tonality, HDRI can even produce an image with a range beyond human vision. One of the limitations of digital imaging (and film before it) is the dynamic range that can be recorded in a single image. Dynamic range is an expression of the ability to discern gradation from darkest to lightest content in a view. A high dynamic range example would be a scene including a home interior and the view of a sunlit field through an open window. No single image could capture this range in one exposure, but several can be processed to include the range. Through computational processing of several exposures, or even versions of the same image, we can create an image with even more dynamic range than human vision. In fact, the dynamic range is often so great that it cannot be fully displayed on a computer monitor. For the final output, we select the most useful range for display.
Image capture of a specimen in transmitted light is a typical example of scientific HDRI. The example shown below is a stained leaf specimen from the collection of the Smithsonian Natural History Museum. The leaf is embedded with resin and held between two glass slides 3 ¼ x 4 inches.