FOCUSSING AND EXPOSURE
Before squeezing the shutter release, indeed before composing the picture in the viewfinder, one must ensure that both the focussing and exposure controls are correctly adjusted on the camera. They are the basic mechanical operations needed to take any good photographs, but they can also be used creatively as we shall soon see.
The camera lens will in theory only render a sharp image of one plane in its field of view at a distance as indicated on its focussing scale. In practice it is found that a distance field about this theoretical distance will also be in apparently sharp focus on the film. The depth of this field can be controlled to a large extent by the aperture setting. A small diaphragm opening will give a large depth of field, while opening the diaphragm will decrease the field drastically until it comes close to single plane focussing at maximum aperture. Keeping the above well in mind, focussing can be accurately performed on the most important element in the photograph while the depth of field can be manipulated creatively by choosing an appropriate aperture. An example of differential focussing is the rendering of the main subject in sharp focus with the foreground and the background out of focus. This gives a suggestion of depth to the viewer. Another example is the sharp rendering of the main subject with the background clutter totally out of focus to remove distracting influences. A final example might be the sharply focussed highlights in the eyes of a subject in a close-up portrait while the remaining features are rendered softer. All these results can be achieved by good use of the depth field scale on the lens and suitable aperture. This is an example of how a limitation in the performance of the medium is brought into good use creatively.
Coming now to exposure, the built-in or hand held meter will give a shutter speed setting to get a correct exposure of a mid-grey area of the subject to be rendered mid-grey on the photograph with a chosen film speed and aperture. By manipulating the film and shutter speed, a wide range of light values can be handled in a ratio of about 1000:1 on mid-grey while still allowing flexibility with the aperture control. A reflected light reading is usually taken with a built-in exposure meter and in this case it is best to take a reading from a small area on the subject that we want to render mid-grey. As in the case of focussing it is important to remember that only a small region of contrast can be reproduced faithfully on film and one should concentrate on reproducing the areas of greatest interest correctly exposed in the photograph. The exposure latitude is a function of film speed and so a small amount of flexibility is also available for creative purposes by the choice of film. It is well to mention here that hand-held meters reading incident light can be convenient and quick to use. However, a reflected light meter can be used to analyse the tonal values of the subject and is in my opinion better for creative work. Spot meters are very accurate in this respect but are expensive and are only needed for specialised work. Finally remember that exposure can be manipulated for effect and one should not feel obliged to use the exposure values as given on the meter. For the moment I will leave it to the reader to think of ways of using the exposure controls creatively. I will only mention silhouetted portraits as a starting point. A later article will have a few more examples on the effects of under and over exposure.
At this point one will realise why I advocated the use of a manual camera for creative photography. Once the three basic controls are mastered the photographer can adjust his camera to produce exactly the result he desires. A mindless automation will never be creative.
My next article will deal with some of the wide range of film types available to the 35mm user.
RL 25/4/85