Most photographs are taken using the available light at the scene to illuminate the subject. Whenever you snap a …
Most photographs are taken using the available light at the scene to illuminate the subject. Whenever you snap a picture outdoors or indoors without resorting to flash, you’re involved in available light photography. In most cases, the resulting pictures should be correctly exposed and colours should be natural looking. Photographers can also take advantage of different light directions to create different effects.
Cloudy skies produce softer lighting.
For example, outdoor light coming into a room can produce some of the best available light portraits, while light coming from behind the subject (backlighting) can create a flattering glow around a subject’s head. Some subjects, such as landscapes, cityscapes, sunrise and sunset shots and night scenes, can only be captured by available light. Mounting the camera on a tripod is mandatory for a few of these subjects but most will benefit from this strategy as it allows the photographer to use smaller lens apertures and low ISO settings to ensure top image quality.
Digital photographers should be sensitive to some important aspects of light in order to capitalise on their cameras’ capabilities. On a broad scale, the angle of the sun, the presence and position of clouds and the clarity of the air can all affect the way images are recorded. More narrowly, the angle and position of the light relative to the subject can dramatically change the appearance of a shot.
However, there may be times when available light is either not sufficiently strong or is poorly positioned with respect to the subject and then photographers are forced into compensatory strategies. The simplest and most obvious is to shoot with flash. Unfortunately, simply using the on-camera flash often produces unattractive results. In this chapter we’ll examine some alternative strategies that can produce better-looking photographs.
How Light Behaves
The intensity of light depends on the distance the light has to travel. Doubling the distance means one quarter of the amount of light reaches the subject. (This is due to the Inverse Square Law: light falls off with the square of distance.) This rule is important with studio lighting as well as for flash photography. The light from most flash units is so attenuated at 10 metres from the camera that it makes little or no impact on camera exposure. Consequently, it’s pointless to use flash for scenic shots at night.
The direction of light determines where shadows and highlights will fall. For landscapes, the time of day and season of the year will be the main factors controlling the direction of the sunlight. In a studio situation, photographers can use reflectors made from sheets of white card or white walls to direct light into shadowed areas in a subject, thereby evening up the balance of light.
The colour of light depends on its source. As explained in ISO and White Balance, different types of light have different colours. The camera’s white balance control can be used to remove these colour casts. Interestingly, if light is reflected from a coloured surface it will take on the colour of that surface. This can have good and bad effects. In landscape shots, light bouncing from warm yellow sand can have an attractive warming effect on tree trunks and foliage. However, light bounced off a blue wall onto a portrait subject can turn skin tones cold, making the subject look ‘dead’.
Most photographers are also aware of how the colour of light changes throughout the day, according to the angle of the sun. Near sunrise and sunset, when the sun is close to the horizon, the light is redder. Sunsets are usually ‘warmer’ than sunrises because there is more dust in the air to disperse and filter the light. This filtering suppresses greens and blues and produces the warmer tones. At sunrise, the amount of dust in the air is less, so sunrise shots are less ‘warm’ than sunsets. However, both are equally attractive to the human eye.
Sun angle can have a dramatic effect on scenic shots. Low sun angles early or late in the day produce long shadows and softer, more dramatic lighting (left), while overhead sun around midday tends to produce harsher, almost shadowless shots (right).
The colour of the light is cooler around sunrise than near sunset, when the air has a higher concentration of dust that scatters the light, creating a warming effect.
Shots taken when the sun is directly overhead in a cloudless sky have snall, very dark shadows. Photographers must rely on interesting compositions to create worthwhile pictures.
But sun angle can have other effects on the ways in which digital camera sensor records the tones in image files. One of the distinguishing factors of digital cameras (especially compact digicams) is the comparatively high contrast their sensors deliver. This is particularly obvious in Australia, where sunlight is relatively strong and the air is usually much clearer than in more highly-populated countries. Sun angles are also relatively high, especially in northern Australia, which extends into the tropics.
However, all digital cameras are designed and manufactured in countries where sun angles are lower for most of the year and the air contains suspended aerosols (water vapour and pollutants) that attenuate light, reducing its overall contrast. As a consequence, the default contrast settings for most cameras will be too high to yield superb outdoor pictures in most parts of Australia (with a possible exception of Tasmania).
In bright conditions, the camera’s exposure metering system may produce washed-out pictures. The histogram shows the tonal bias in the shot pushed towards the right.
Underexposing by -0.3 EV will produce an image that is easier to print than the shot with the metered exposure.
Several strategies can be used to produce image files that will make high quality prints – either without or after some simple editing.
The default flash setting (left) can produce harsh, unflattering results. Reducing the flash output by 1.0EV is kinder and more flattering to the subject.
Most cameras have TTL (through-the-lens) systems that measure the amount of flash light reflected off the subject and shut down the flash when enough has been delivered. Consequently, it’s easy for photographers to simply use the auto flash setting for all flash shots. However, better results can be obtained with a few simple strategies.
The red-eye effect can be prevented by:
Many image editors include easy red-eye removal tools. A few entry-level DSLR cameras are supplied with built-in software that can detect and correct red eyes in flash shots. This software is relatively common in compact digicams.