Fluorescent imager with limited variable gain

A fluorescent imaging device (100) includes an imaging unit (106) including a camera (102) with an optical detector that is configured to acquire a fluorescent image of a fluorescing sample, the image including raw pixel values. A user interface (104) is configured to display an image formed from display image pixels derived from the raw image pixels. A distance sensor (110) is configured to measure a distance to the fluorescing sample. A distance between the optical detector and fluorescing sample is to be determined from the measured distance. A processing unit (108) is configured to obtain a gain value, match the determined distance to a distance value associated with a respective gain range and impose limits of the gain value range onto the gain value to determine a limited gain value. The limited gain value is to be applied to the raw image pixels to derive display image pixels.