Langford (2000), states there are six features of lighting to bear in mind when taking a photo; Quality, Direction, Contrast, Unevenness, Colour and Intensity. He advises to looks at each of these features one at a time and how they relate to different kinds of equipment and techniques.
Quality of Light
Quality of Light refers whether the light is ‘hard’ or ‘soft’. Of course, light doesn’t have physical attributes the terms hard and soft refer to the type of shadow the light is causing an object to cast. Hildebrandt (2013) relays that hard light is defined by “…strong, well defined shadows with a high degree of contrast” and that soft light is “characterised by soft or not easily defined shadows and low contrast
Direction
The direction of light determines when shade will fall on the subject. The use of directional lighting can affect the texture of and form of the subject (Langford 2000). As we’re used to seeing light from above, due to the sun, people typically see lighting from above as more acceptable and pleasing. Lighting from below tends to relay an eerie tone, particularly in faces. Flat lighting, lighting parallel to the subject is named as such due to producing a very flat looking texture to the subject as it fills in any shadows. The opposite is true when side or top lighting, shadows are created therefore creating texture.
Contrast
Contrast relates to the difference in light from the lit parts of the subject to the shaded parts. Due the way film and digital sensors work in the present day, their dynamic range (the information that can be recorded from pure black to pure white) is significantly less than the human eye can detect. This can lead to, when exposing for highlights, to have darker than intended shadows and conversely, when exposing for shadows, blown out highlights. The problem can be remedied with several different methods such as creating HDR (high dynamic range) images by way of compositing differently exposed images, and today’s higher end cameras can recover more detail from RAW files without too much loss in quality. You can also use fill lights or reflectors, or moving away from the light source will create less light fall off giving a more gradual fade from light to shadow.
Unevenness
Langford (2000) describes unevenness as unwanted light fall off due to a (most likely hard) light source being too close to the subject. This links to the quality and a contrast of light and can be remedied by utilising the inverse square law.
Colour
Colour is based on the spectrum of light and where the most energy lies in the spectrum, for example most domestic lightbulbs (like tungsten or fluorescent) have more energy in the red and yellow wavelengths and less in blue, the inverse is true for most flashes though to much lesser ratio. Midday sun produces what is called ‘white-light’ which is relatively equal wavelengths in the light spectrum.
This colour of light is referred to as colour balance or temperature and is measured in Kelvins. Tungsten light is around 3200K whereas white daylight is around 5500K.
Intensity of Light
Intensity of light can mostly be controlled by exposure settings in the camera. There may be some trade-offs when exposing for light however. For example, if you were shooting a portrait and wanted a shallow depth-of-field shooting at f/1.4 in really bright light, you would need a really high shutter speed, possibly one quicker than the equipment will allow. Similarly, in low light, you may want to shoot a 1/60 a second to reduce motion blur, and shoot at f/8 to ensure best results from the lens, this will mean you need to raise your ISO and therefore reduce the quality of the image due to noise being introduced and a reduced dynamic range.