Photo manipulation involves transforming or altering a photograph using various methods and techniques to achieve desired results. Some photo manipulations are considered skillful artwork while others are frowned upon as unethical practices, especially when used to deceive the public. Other examples include being used for political propaganda, or to make a product or person look better, or simply for entertainment purposes or harmless pranks. Depending on the application and intent, some photo manipulations are considered an art form because it involves the creation of unique images and in some instances, signature expressions of art by photographic artists. For example, Ansel Adams employed some of the more common manipulations using darkroom exposure techniques, burning (darkening) and dodging (lightening) a photograph. Other examples of photo manipulation include retouching photographs using ink or paint, airbrushing, double exposure, piecing photos or negatives together in the darkroom, scratching instant films, or through the use of software-based manipulation tools applied to digital images. There are a number of software applications available for digital image manipulation, ranging from professional applications to very basic imaging software for casual users.Photo manipulation dates back to some of the earliest photographs captured on glass and tin plates during the 19th century. The practice began not long after the creation of the first photograph (1825) by Joseph Nicéphore Niépce who developed heliography and made the first photographic print from a photoengraved printing plate. Traditional photographic prints can be altered using various methods and techniques that involve manipulation directly to the print, such as retouching with ink, paint, airbrushing, or scratching Polaroids during developing (Polaroid art). Negatives can be manipulated while still in the camera using double-exposure techniques, or in the darkroom by piecing photos or negatives together. Some darkroom manipulations involved techniques such as bleaching to artfully lighten or totally wash-out parts of the photograph, or hand coloring for aesthetic purposes or to mimic a fine art painting. In the early 19th century, photography and the technology that made it possible were rather crude and cumbersome. While the equipment and technology progressed over time, it was not until the late 20th century that photography evolved into the digital realm. At the onset, digital photography was considered by some to be a radical new approach and was initially rejected by photographers because of its substandard quality. The transition from film to digital has been an ongoing process although great strides were made in the early 21st century as a result of innovation that has greatly improved digital image quality while reducing the bulk and weight of cameras and equipment.