All kinds of models are built and used for studio photography, but one particular kind, the scale model, is a drastic form of substitute. Such models are not intended as miniatures, or objects in their own right, but to simulate the full scale thing. As a solution to constructional problems they are drastic in as much that if the fall short of perfection b y even a tiny amount they fail utterly, yet they are very tempting as a way of undertaking otherwise impossible images. They have a special value for spectacular and fantastic subjects, particularly large ones.
In advertising photography, where budgets are usually high, professional model builders are frequently used. Both skill and imagination are need in preparing a model, and a professional has the benefit of experience. One of the hidden problems in scale model photography is the uncertainty of knowing whether or not the result will pass the minimum standards of being convincing. It is a help to know the likely specific problems (for instance, trees and vegetation are especially difficult in a landscape model) and ways of diverting attention from them (deliberately obscuring the lighting, for instance, by choosing a night time or contre-jour setting).
The first major principle is that the model is built for the camera, and not as an independent object. Specifically, this means that some effort can be spared by building no more than is necessary – just what faces the camera and not the back – that perspective can be built into the model to enhance the impression of scale, and that the degree of the detail should be just sufficient for the resolution of the photography. The matter of sufficient detail is important, because in most models it is this rather than the basic structure that takes up time, yet finely resolved detail is ultimately the most convincing quality of a model. All of this, naturally, benefits from advance planning.
In shooting, the photographic techniques must also help to compensate for the lack of scale. The depth of field, which is small at shorter distance, needs to be restored; this can be done partly by using a small aperture, partly by compressing the perspective of the model, and partly by using a wide angle lens. A view camera also has the possibility of movements, which can bring more of the subject into focus if carefully used. A wide angle lens has the additional advantage of exaggerating the perspective, so enhancing the sense of scale.
The lighting also plays an important part, and for realism should be scaled accordingly. Direct sunlight is, to all intents, a point source of light, and can be mimicked in the studio only by a very small bulb or flash unit. Simulation of cloudy weather allows more diffusion, while night scenes have great flexibility and can make use of miniature modeling lamps.