ABSTRACT
The second half of the nineteenth century saw the progression from early experiments with light-sensitive compounds to the first cameras and photographic films becoming available to the general population. It developed from the minority use of the camera obscura as a painter's tool, through the first fleeting glimpse of a photographic image in a beaker containing silver compounds after light exposure, to the permanent rendering of the image, and then to the invention of the negative–positive photographic process used today to produce an archival image. During image capture, light from a scene is refracted by a lens and focused on to an image plane containing a light-sensitive material. Refraction is the deviation of a light ray as it passes from one material to another with different optical properties, and is a result of a change in its velocity as it moves between materials of different densities. In traditional photographic materials, exposed light-sensitive silver halide crystals form a latent image.
