Lighting equipment for portraiture

While complex equipment in the hands of experienced professional photographers should guarantee attractive, correctly exposed and well-lit portraits, in many cases photographs taken with basic equipment can be just as attractive – and also more spontaneous when the basic equipment is used effectively. (Source: Camera House.)

The main types of artificial lighting for photographers are flash and continuous light sources.

Flash: When using flash you’re effectively shooting ‘blind’. You can’t see the effect the flash produces until after the shot is taken. This can have unfortunate consequences.

Most snapshooters have taken photos using their camera’s built-in flash so they should be aware of potential problems. Subjects can end up either with their eyes closed or looking demonic because of reflections of the flash light from the blood-rich retinas at the back of their eyeballs.

The top photo shows the way direct flash can make the subject’s eyes appear red because the light is reflected directly from the retinas at the back of each eye. The lower photo shows the effects of red-eye correction, which is provided in most image editing software.

While you can find ‘red-eye reduction’ modes in virtually all cameras, people often forget to engage them and, even when used, they often produce disappointing results. Post-capture correction can be equally unsatisfying since – as with all things – a little knowledge can be dangerous. In the hands of a competent user and with capable software, correcting red eyes in flash shots should be easy and successful.

Knowing what lighting is available and understanding how to use it in different situations can overcome these problems. Readily available flash options range from the built-in, low-power flashguns on entry and mid-level cameras through to complicated and expensive studio set-ups that are beyond the reach of amateur photographers.

Between these extremes are accessory flashguns that are more powerful than built-in flashes and much more adjustable and easier to use than studio systems. Fortunately, you can do a lot with relatively simple gear; in many situations you may not even need to use the flash at all.

The main advantage of flash is its very short exposure time which captures an instant in time. This minimises the risk of blurring, although the extreme brevity of the exposure increases the risk of the subject’s eyes being shut.

On-camera flashguns are convenient and affordable. But the light they produce can be very harsh, unless it is diffused with a clip-on translucent panel, as shown in this illustration.

When taking group portraits with flash you often find at least one person in the group has their eyes shut. You need to take a lot of shots in order to overcome this problem – and check the sequence carefully to make sure at least one of them is usable.

Interestingly, there’s a scientific way to go about it. The 2006 Ig Nobel Prize for mathematics was awarded to Nic Svenson and Piers Barnes of the CSIRO, for calculating the number of photographs you must take to (almost) ensure that nobody in a group photo will have their eyes closed. You can find their original paper at www.archive.ph/Oh9yr.

The average number of blinks made by someone getting their photo taken is 10 per minute. Factors making people blink more than normal include nervousness, dry air, stress, tiredness, wind, contact lenses, red-eye reduction pre-flashes and social behaviours such as not telling the truth, fancying the photographer and the photographer talking about how often people blink in photos. The conclusion for calculating the number of photos to take for groups of less than 20 states: divide the number of people by three if there’s good light and two if the light’s bad.

Continuous light sources range from the portable and relatively inexpensive LED panels through to studio lights that can be accessorised with hoods, snoots and reflectors. They have three major advantages over flash lighting:
1. You can see the effect of the lighting immediately before taking the shot.
2. They use a lot less power, produce a lot less heat and are more comfortable for subjects.
3. They can be used for video as well as for shooting stills. (Flashguns are totally unsuitable for video.)

Either type of light source can be combined with natural lighting to ‘fill in’ dark shadows. In fact, this is often the best (and sometimes only) way to use an on-camera flash, as we explain in Chapter 7 of Portraiture pocket guide. (Chapter 6 of the guide provides information on lighting techniques that can improve the rate of ‘keeper’ shots.)

Light and the inverse-square law

Before you can begin to work with light it’s important to understand how it works. This is defined by the inverse-square law, which applies to all forms of electromagnetic radiation and explains why light becomes brighter when it is moved closer to a subject and fades as it is moved further away.

The term ‘square’ quantifies the amount by which intensity declines. This law is used to calculate the difference in the illumination of a subject as it is moved closer to or further from the light source. Hence its importance in photography, particularly studio portraiture (although it can also be relevant in other environments).

This diagram shows how the intensity of the light from any light source declines with distance. The changes are indicated in f/stops for easy reference.

To provide a practical example of the concept in layman’s terms: if you move a light source that was one metre from the subject to two metres away, you reduce the intensity of light falling on the subject to one quarter of the amount reaching it at one metre’s distance.

Similarly, if you want to halve the amount of light on the subject, increase the distance by a factor of 1.4 (the square root of 2) – which means moving the light to 1.4 metres from the subject. The reverse is also true; you can increase the strength of the light by 1.4 times by moving a light that is two metres from the subject to one metre.

See advice on cameras and lenses for portraiture

Excerpt from Portraiture pocket guide, by Photo Review tech editor Margaret Brown.

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