Light makes photography. Embrace light. Admire it. Love it. But above all, know light. Know it for all you are worth, and you will know the key to photography.
The word photography is derived from two Greek words and basically means drawing with light. Sir John Herschel is generally credited with coining the word and introducing it to the public in a lecture on the subject to the Royal Society in London in 1839. Details of the history of photography and its development can be found in a number of books. An online search using Google will render a multitude of references of the early days of photography.
For those of you old enough to remember, film was probably the first medium of image capture that you used. While some photographers still use it today, the vast majority of image capture is through some form of digital photography. Regardless of how you capture images, light is still the most important aspect of that process.
In a recent issue of Photo World, Wayne Lynch notes the importance of four aspects of light. After reading it, I decide that the word DISC is an easy acronym to remember these four aspects of light.
D – direction. Where is the light coming from?
I – intensity. How bright is the light?
S – source What is the source of the light
C – colour. What colour is the light?
This is relatively simple to decide, either the light is coming from a particular direction, or it is not. The source often does not matter. Light can come from your right or left, over your shoulder, i.e., from behind you, or from your front. Each direction will cast different shadows. Perhaps, the one exception is daylight on overcast days. The light seems to come from everywhere, although subdued when compared with bright, sunny days. The light from overcast days is like being inside one giant soft box.
Light coming towards you is usually required to make silhouettes. If the sun is behind you, then your subject will be fairly evenly lit. If the light comes from the side, then this may make the lighting in your image more interesting and often more dramatic. Depending on the direction, shadows will be to the right or left of your subject. When the sun is overhead, then there are very few shadows and image taken during these times can look very flat.
Intensity is a measure of how strong the light is. In the case of sunlight, for example, are you dealing with the warm light of sunrise and sunset that provides long, soft shadows, or are you shooting in the middle part of the day when the sun is overhead and the shadows are very strong and harsh. In the case of flash photography, shadows can also be soft or harsh depending on the intensity of the flash and whether or not accessories such as diffusers or reflectors are used. Such accessories can also be used to modify the effects of sunlight.
Often, if you are shooting indoors, you may have to deal with artificial sources such as fluorescent or incandescent light. The factors of intensity are also valid here. One other source that is becoming more popular are LED lights. These are usually found in a set of LEDs that are available in camera stores and industrial supply warehouses. Some of these are simply ON/OFF with the colour of the light being constant and others allow the colour of the light to be adjusted over a variable range.
The source is pretty well self-explanatory. Are you working in sunlight, cloudy overcast sunlight, moonlight, flash, artificial or some combination? Generally, single sources are the easiest to deal with in terms of the exposure variables that are required. Mixed light sources may require some additional thought on the exposure variables to be used and on any White Balance considerations in post-processing.
One of the most common scenarios with mixed light is when flash is used as a fill light in portrait photography. I also use this combination on occasion when shooting macros of flowers outdoors. Over the next few months, I will also be experimenting with the use of LED panels as fill light for outdoor flower photography.
Light has colour. We may not always think of it as having colour, but it does. Perhaps the most obvious reference that most of us will have are the reds, oranges and pinks of sunrises and sunsets. For the technical readers, colour has a temperature, not one that you can measure with a thermometer, but a temperature nevertheless.
The colour temperature of a light source has to do with the physics of what are called black-body radiators, but it has nothing to do with the human body. It, colour temperature, is a characteristic of visible light and is stated in the unit of absolute temperature, the Kelvin and has the symbol K.
Colour temperatures over 5,000°K are called cool colours while temperatures below about 2,700° to 3,000°K are called warm colours. The following table gives the approximate colour temperatures in degrees Kelvin for a variety of different light sources. These temperatures are generally characteristic of the medium, but some variation may be present.
Source Temperature °K
Candle Flame 1,850 – 1,900
Incandescent Lamps 2,700 – 3,300
Studio lamps 3,200 – 3,400
Moonlight 4,100 – 4,150
Tubular Fluorescence lamps 5,000
Vertical Daylight, Electronic Flash 5,500 – 6,000
Daylight, overcast 6,000 – 6,500
Shade in daylight 6,500
Shade in partly cloudy sky 7,000
Knowing the colour of the light for your image is necessary to ensure a proper while balance setting. Even if you use Automatic White Balance, you may wish to make slight corrections to white balance in post-processing. To assist in any post-processing corrections, most photographers will make use of a grey card or an accessory such as the Colour Checker Passport®.
The next time you set out to do some photography, make a conscious effort to assess the lighting conditions in your image. Use the acronym DISC to evaluate the light and adjust your exposure accordingly. As well, the determinations you make from your DISC evaluation may prompt you to change the time of day that you will take your photo. Maybe you should have gotten up at 4:00 am to take that photo!