How to use your Camera to shot good Pictures/Photo (Exposure memory; Exposure compensation)

Exposure memory

Even the most accurate through the lens exposure meter can be fooled by a subject surrounded by large dark or light areas, subjects which are predominantly back lit, or those against unusual backgrounds. These can influence the meter, providing false information about the light level. Thus the main subject is over-exposed if the meter reacts to a large expanse of black background and, conversely, underexposure of the subject results if it is back lit or surrounded by a large bright area.

Some cameras have a built-in exposure memory which ensures that the subject is given the appropriate exposure to show detail regardless of the surroundings. To use the memory facility effectively take a meter reading close up to the subject, or even from a substitute object of the same tone as the main part of your photograph, and lit in the same way.

Often the exposure reading is taken by gentle half-way pressure on the camera shutter release button—this activates the meter circuits. Holding the button in the same position while moving away to photograph the entire subject keeps the camera set to whatever aperture and shutter speed have been preselected during close-to light metering. The exposure is made without releasing this gentle pressure on the shutter release.

The disadvantages of this method are that if you ‘let go’ the memory is overriden and you are back to square one. Care must also be taken neither to release the pressure sufficiently for the camera meter to take its reading from new information, nor to squeeze a little too hard, trip the shutter and waste a frame. This type of exposure memory or exposure hold is most commonly found on 35mm non-reflex cameras. Some sophisticated cameras have a special memory button which is less precarious to use. The memory button may be the type which is held in once the light reading has been made; or some electronic cameras retain the exposure memory for several seconds after once pressing the memory button. In the latter case a viewfinder light signals that the memory is in operation.

Exposure compensation

Many automatic SLR cameras have a means for overriding the meter’s settings to compensate for ‘difficult’ lighting conditions with certain subjects. This is usually in the form of a dial providing two full f stops compensation over and under that set. The settings are often graduated in 1/3 or ‘1/2 stop steps and can either be marked –2, – 1, + 1, + 2 or x , x1/2, x2, x4. In both cases the respective settings indicate two stops less exposure, one stop less, then one stop more and two stops more exposure than that set. For back lit subjects, or subjects against a bright background the dial should be set to plus (that is more) compensation. This provides detail in the main part of the subject and the amount of compensation required depends on the amount of back light. A dark background or large dark unimportant areas of the picture seem to occur less frequently, but minus compensation (by giving less exposure) gives full detail in the main or lighter parts of the subject.

Some cameras have back light compensation only, and this often provides fixed 11/2 stops more (plus) exposure. If your camera lacks the EV (exposure value) compensation dial you can

EV compensation scales are usually only found on automatic SLR cameras. The Chinon CE-4 gives ±one stop and only the 1/3 stop steps are marked. The Contax 139 can provide ±two stops compensation achieve the same degree of exposure control, and more, by adjusting the film speed dial. Move the film speed indicator to half the ASA of the film in use to increase exposure by one full stop. For example if you are using 100 ASA film, set the film speed dial to 50 ASA. This tells the camera that less sensitive film is being used so the built- in meter automatically compensates. Doubling the film speed setting decreases the exposure given by one full stop—if you are using 100 ASA set the dial to 200 ASA.

It is of course vital that the dial is returned to its correct setting when returning to ‘normal’ photography with lighting which needs no compensation. Some cameras have a signal in the viewfinder to show when dial-in compensation is in use, but there is no signal to remind you that you have adjusted the film speed dial. If you forget to readjust the compensation control or film speed dial subsequent frames will be over- or under-exposed.

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