Correction of uneven illumination (vignetting) in digital microscopy images

Background: Many digital microscopy images suffer from poor illumination at the peripheries ( vignetting), often attributable to factors related to the light path between the camera and the microscope. A commonly used method for correcting this has been to use the illumination of an empty field as a correction filter (white shading correction). Aims: To develop an alternative shading correction method that does not require this additional image. Methods/Results: This report outlines an alternative shading correction method that is based upon the intrinsic properties of the image, which are revealed through Gaussian smoothing. The technique can be implemented within Adobe Photoshop or other graphics editing software and works well with both haematoxylin and eosin and immunohistochemical images. Conclusions: This technique provides an effective means of optimising digital microscopy image appearances for printing, image analysis, or telepathology.