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BASIC PHOTOGRAPHY

John Atkinson

In some ways, digital photography and the earlier optical/chemical photography share

some common basic principles with reference to camera settings.

In order to produce a technically acceptable picture, the principal requirements are:

The images should be:

1. Sharply focused2. Correctly exposed3. The colours should be as true as possible.In earlier conventional photography, the photographer would have to decide on and

choose the most suitable type of film for the application in hand. Apart from brand

and type, the main consideration would then be one of sensitivity or film speed. A

situation where lack of ambient light is the main problem, would require a relatively

fast film. The main disadvantages of a fast film are visible grain and relatively lowcontrast in the final image. Once the film is loaded into the film camera, the film

speed will be the same for all exposures on that particular film. The modern digital

camera has the advantage that the sensitivity or ISO setting on the camera can be

changed for each frame, if so required.

So perhaps a good starting point, would be to determine the most suitable ISO setting

for each or each group of exposures. For example, a brightly lit, daylight landscape

scene would benefit from the selection of a relatively low ISO setting, as this would

provide a higher contrast image and would at the same time, result in less noise.

The term noise in digital photography can be likened to grain in the earlier version.

Looking at the opposite situation, where there is little available light and one can not

use supplementary lighting, the only alternative is to increase the ISO setting in order

to obtain suitable exposure levels and shutter speeds. A typical example of thissituation could be in dimly lit aquarium applications, where flash is not permitted.

FACTORS WHICH AFFECT EXPOSURE

The total exposure applied to the storage media, whether it is a film or electronic

memory card, which must pass through the camera lens as light, depends on:

1. The lens aperture2. The shutter speed

Lens apertures are related to f numbers, sometimes also called f stops; while

shutter speeds are measured in seconds, or fractions of a second.

The actual level of exposure for a correctly exposed image will also depend on certain

other conditions, which are:

1. Ambient light2. The subject and type of image required. e.g. high key portraits or night scenes.Almost all modern digital cameras are capable of producing very acceptable

results in the basic requirements mentioned, by using one of the provided

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PROGRAM settings. Most cameras have a basic P setting and this may be

further refined by then going into other settings within the P range. These other

settings are usually denoted by pictorial symbols and may include such settings as:

portraits, distant landscapes or mountain scenes, night time scenes, sporting

scenes, a setting for photographing text and even possibly one for picturing

fireworks

The P setting used on its own will give very acceptable results for mosteveryday type of snapshots.

Before going into the other more specific settings, let us try to understand the

effects produced by these settings and some of the terminology.

Terminology

ISO International Standards Organisation ASA American Standards Association DIN German Industry Norm (Logarithmic Scale) Depth of Field. - The distance in front of and behind an object within

which other objects would appear to be in focus.

Depth of Focus. The amount by which the distance between a cameralens and film, plate, or sensor can be varied, without altering the sharpness

of the image.

APERTURE - A unit expressed in f numbers or stops, which is aA ratio of Focal length of lens

Diameter of lens

Note Since the f value is inversely proportional to the lens diameter, it follows that

a large lens diameter will have a relatively smallfvalue and vice versa.

FOCAL LENGTH - The distance between the centre of the lens andthe sharp image of an object at an infinite distance from the lens.

EXPOSURE VALUE (EV) . The use of these values is not in commonuse on modern digital cameras as a marked setting which is mainly due to

the auto setting facilities. (used for lightmeter settings) (AE & AEL

Settings)

Having already thought and spoken about ISO settings on digital cameras, let us now

consider some of the other settings which we can choose to use if we so wish.

While still in the Auto mode we can now see that a further selection is available.These are: P or Program mode with its further refinements, A or Aperture priority.

S or Shutter priority, and M for manual mode.

A Aperture Priority. With this setting, the operator can initially pre-selectthe chosen aperture via another control such as a command dial or sub-menu.

The correct shutter speed will then be automatically selected and displayed on

the cameras viewing screen or data panel. In this way the operator can control

the extent of his depth of field.

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S Shutter Priority. In this mode setting the operator will select the desiredshutter speed via the command dial or sub-menu. The correct aperture will

then be automatically selected and displayed on the viewing screen or data

panel. In this instance the operator can control the shutter speed when it is of

prime importance.

M Manual Control. - In this mode, the photographer is able to 0veride the

automatic settings previously mentioned. This is a most useful feature when the

photographer wishes to create a special effect e.g. a high key portrait or a special

mood scene. This method is also usually adopted when it is important that the final

image requires a very exact exposure in its final form. Most automatic cameras

whether film or digital types measure the reflected light in a particular mode. A more

accurate exposure value may be obtained by taking a reflected light reading and

another incident light reading from the subject position towards the camera

position, and then using an average of the two values. In this instance the camera

setting is set to M and a separate portable hand held light mete is used to take the

two readings. These light meters are often calibrated and marked in both EV and f/

Shutter speeds.

Manual Focus. This is a useful facility when ,for example, in fast action sports

pictures, when there is insufficient time for the auto focussing to be effective, the

photographer can manually focus on a pre-determined spot, so that the moving subject

will be in sharp focus when it happens to be in that particular spot.

Shutter Speeds. When shooting a moving subject, you can either freeze the

motion or capture the sense of movement, by adjusting the shutter speed.

Fast shutter speed freezes the motion of the subject, while a slow shutter speed

photographs the traces left by the subject movement. e.g. Waterfalls.

Sometimes, one may wish to freeze a moving subject, but also maintain a sense of

motion. A typical example of this is photographing a motor cyclist so that the

machine and rider are in sharp focus, but the background is blurred to give an

impression of speed...

In this instance, the photographer will have to choose his camera position carefully, so

that he is able to pan the camera in order to follow the moving subject. It is essential

to manually focus the camera on a pre-determined spot i.e. where the frame will be

exposed, and then lock this focus setting. A shutter speed of about 1/200 sec. should

be adequate to freeze the subject and movement of wheels & spokes. However, the

panning action may be sufficient to blur the passing background. The optimum shutter

speed to produce the desired effect may have to be varied for each particular situation

because of the many other variable factors.