A definition of Blooming

An effect caused by charge spilling over from full photosites on the sensor to adjacent cells. This is often observed in images of trees around the edges of leaves and branches, where there is high contrast between darker and lighter areas. Sensors equipped with anti-bloom drains allow this excess charge to be discarded, although as these take up space on the sensor they reduce the space left for light-sensitive photosites, thus reducing the sensor's sensitivity.