ABSTRACT
The choice of a lens for an application is governed initially by knowledge of its general properties. These include optical parameters such as focal length, aperture, field coverage and resolution capabilities, as well as mechanical features such as controls, scales, mount type and fitting. The coverage of the subject by the lens related to format area is usually quoted in terms of the field angle of view (FOV). For photography this is generally quoted as the FOV for the diagonal of the format, this being the maximum value and a selling point. For applications such as multi-projector or multiscreen presentations, involving two or more projectors, or for stereoscopic photography with multiple-lens cameras, the lenses used must be matched in focal length to 1 per cent or better. The behaviour and suitability of a lens for an application may be evaluated by the user in actual practical tests.
