Reversal prints are produced by exposing photographic printing paper directly within a large format camera. The paper is developed normally, producing a negative image. The paper is then bleached to lighten the exposed areas and render them insensitive to further exposure. A second over-all exposure to light causes the formerly light areas to darken during a second development. The result is a positive print made without the use of an intermediate negative. The process is similar to dry plate as the paper is quite slow compared to film. The resulting image is mirror-imaged as it is made by direct exposure within the camera.
This video shows the full exposure and darkroom reversal process of an image exposed in a 4x5 large format camera.