luding over or underexposure or treating the negative to cover lines or remove unwanted objects or people from the image. If arts are masked off or cut out of the photograph, the natural gradients of the photograph are disturbed and an unnatural sharp edge appears in the final image. Because when the film is developed, the clumping of molecules forms an emulsion grain, if this grain is subsequently disturbed by pen, pencil, or paint, or a specific section is erased the alteration is easily detectable. If parts are added to a photograph after it is developed, they must match exactly before the composite can be convincingly rephotographed. Because any difference in proportion, color, brightness, focus, contrast, lighting, or camera angle is an immediate perceptual signal. Any additions must be photographed under nearly exact conditions as the primary photograph and reflect the exact position from which it would have naturally occurred. Even when altered photographs are rephotographed, alterations such as retouching and montages never disappear entirely because traditionally photography is an analog representation and therefore difficult to alter without obvious effect. Unlike a digital image, which is broken down into small separate units, the traditionally processed photograph appears as a continuous unbroken sequence of subtle gradients. This makes it extremely difficult to rework a photograph because there are no individual units or cells in a grid, from which to work with after the image is fixed. There are only ever increasingly and subtle gradations that are nearly impossible to retouch convincingly. The final images surface is so smooth and clear that retouching would be very obvious. To "fake" a photograph it is necessary to have mastered all of the skills in doing so. Otherwise, it will be even easier to detect the falsehood of the photograph. A photograph that has been faked must have all the aspects of a real photo...
