1. An instrument for scanning at least a part of a large specimen mounted on a specimen holder, the instrument comprising a light source, at least one lens to focus light from the light source, a detection system that comprises at least one detector, a computer programmed and configured to: a) take a plurality of measurements of each pixel at a plurality of exposure values; b) receive, process and store data received from the at least one detector; c) control a power output of the light source; and d) control the movement of the specimen holder during scanning and a gain of the at least one detector to produce a digitized image of the at least one part of the specimen with a larger dynamic range than a dynamic range of the detection system.