A digital image of a Zostera marina leaf. a) An image of a Zostera marina leaf exhibiting the typical belted shape. Related area is commonly approximated by the product of length and average width. b) The display of the image of the leaf using a darker tonality reveals pixels placed beyond the peripheral contours, which do not belong to the image and whose presence is explained by humidity- noise-related effects. Improper identification of the peripheral contour of the leaf image due to spurious entries can lead to miscalculation of related area.