Underexposure A condition in which too little light reaches the film, producing a thin negative, a dark slide, or a muddy-looking print. Vanishing point is the point at which parallel lines, viewed obliquely, appear to converge in the distance. Variable-Contrast Paper Photographic paper that provides different grades of contrast when exposed through special filters. Vignetting A fall-off in brightness at the edges of an image, slide, or print. Can be caused by poor lens design, using a lens hood not matched to the lens, or attaching too many filters to the front of the lens.
Viewpoint is the position of the camera in relation to the subject.
Zoom Lens A lens in which you adjust the focal length over a wide range. In effect, this gives you lenses of many focal lengths. Zone system is the method of determining exposure and development required for individual scenes, invented by Ansel Adams. It is based on analysis of subject luminosities in terms of ten gray tones, labeled zones 0 through X and previsualizing them as print densities. By measuring each subject luminance with a hand meter it is possible to determine how much the range of values must be contracted or expanded by negative development control to give the required values in the print.