oversharpness

Oversharpening is an image processing artifact that occurs when an image is sharpened too aggressively. While sharpening is a technique used to enhance the detail and definition of an image, excessive application can lead to undesirable visual effects. The most common symptom of oversharpening is the appearance of halos around edges within the image. These halos are typically bright lines adjacent to dark edges, or dark lines adjacent to bright edges. This happens because sharpening algorithms work by increasing the contrast between adjacent pixels. When this increase is too pronounced, it creates artificial edges that are not present in the original scene.

Another characteristic of oversharpening is the amplification of noise. Image noise, which can be random variations in brightness or color, becomes more apparent and distracting when subjected to excessive sharpening. This can result in a grainy or speckled appearance, particularly in areas of smooth tone. In severe cases, oversharpening can also lead to a loss of subtle tonal gradations, making smooth transitions appear posterized or banded. While the goal of sharpening is to improve perceived detail, oversharpening can paradoxically make the image look less natural and more artificial. Careful application of sharpening, often with fine-tuning of parameters like radius and threshold, is crucial to achieve the desired effect without introducing these artifacts.