The process of altering an image, especially to remove defects or change its content. Retouching includes correction of mechanical problems, such as removing shadows or dust, as well as alterations to the image. Retouching may be performed with pencils, a brush and inks, or with an airbrush on a negative, before printing, or on a print. Digital retouching, which makes changes to pixel values to enhance or change the appearance of the image, is typically done on a computer before printing.