A flow meter, and related method, include a coupler adapted to couple to a drip chamber, a support member operatively coupled to the coupler, an image sensor and a backlight. The image sensor has a field of view and is operatively coupled to the support member. The backlight is adapted to illuminate the image sensor to expose the image sensor such that the field of view of the image sensor at least partially images at least a portion of the drip chamber. A processor receives image data from the image sensor to select a region of interest of the image sensor, determine whether a pixel of the image sensor is within the region of interest, activate the at least one light of the backlight when the pixel of the image sensor is within the region of interest, and expose the pixel of the image sensor.