Lighting for Portrait Photography (Part 1): Behavior of Light

Light is the raw material of a photographer. Much assubject from many different angles. High contrast
the painter works with paint and the sculptor workslight sources produce shadows with a hard edge,
with stone, the photographer works with light. Thiswhile low contrast light sources produce shadows
analogy is not precise however, because as thewith a soft edge. This is because with a high contrast
painter and sculptor work with actual materiallight source, where the rays all approach the subject
substances, the photographer works with a form offrom approximately the same angle, no light enters
energy. Understanding the behavior of this form ofthe edge of the shadow and the shadow's edge
energy that we call light, is foundational to yourremains distinct. A light source's relative contrast is
success as a portrait photographer. A painter maygenerally determined by the size of the light source
not need to know the chemical and physicaland its distance from the subject. The sun on a clear
properties of each component of her paints, but sheday is relatively small in our sky, and therefore it is a
must completely understand how to blend thehigh contrast light source producing hard edged
different colors, and how the paints behave as sheshadows. On a cloudy day, the light from the same
applies them to the canvas. Just as a painter orsun is spread out and diffuse. Effectively the entire
sculptor must gain masterful insight into the behaviorsky becomes a low contrast light source, producing
of the raw materials of their arts, so must thevery soft edged shadows. In the studio, we have
portrait photographer gain a keen understanding ofmany light modifiers available to us, to control the
the behavior of light.effective size of the light source and thereby control
The first prerequisite for photography is light beingthe level of contrast. For any given size of a light
emitted from a source. Just think about it, withoutsource, as it is positioned farther and farther away
light, photography is impossible. Light may be emittedfrom the subject we see that it effectively becomes
from a natural source, such as the sun, or from ansmaller and smaller, yielding higher and higher levels of
artificial source, such as strobes or constant lightcontrast, albeit lower and lower intensity.
sources. In 1931, the strobe was developed for useLight acts on any subject it may strike. This much
in still photography by Harold Edgerton [ an electricalmay be obvious. But every subject also acts on any
engineer from MIT. Today, the strobe is by far thelight that strikes it. A subject may act on light in
most used light source in the portrait studio.three distinct ways: refraction, absorption, and
Advantages of strobe lighting for portrait studioreflection. Refraction is the bending of light waves as
photography include: reasonably precise control ofthey pass through a transparent material such as
light intensity and light color temperature, low heatglass. In fact, the refractive property of glass is what
generation compared to a constant light source, andis manipulated within the photographic lens, to focus
low power consumption for the amount of lightan image onto the film (or digital image sensor).
output.Absorption is the process whereby certain materials
The most important property of light to the portraitconvert light energy into some other form of energy
photographer is the light's intensity or brightness.(usually heat). The absorptive property of a black
There are several ways of controlling the intensity ofpainted foam core board may be used by the
light striking the subject. In the studio, the powerphotographer to selectively "subtract" light, so that it
supply of modern strobes may be adjusted. Thedoes not bounce around the studio in an undesirable
strobes may be positioned farther away from theway.
subject. Outdoors, you may take advantage of cloudOf the three ways a subject may act on the light
cover or the overhang of a tree or building, or evenstriking it, reflection is the most important to the
the time of day, to control the intensity of thephotographer. Reflection is an abrupt change in the
incident light on the subject. These methods aredirection of propagation of light waves that strikes
effective for controlling the average (overall) lightthe surface of the subject. In direct reflection, the
intensity of the composition. Many devices have beenlight rays bounce from a smooth surface at the
developed to control the relative intensities of lightsame angle at which they hit it. The intensity of the
(specular highlights) of specific areas within adirect reflection mirrors the intensity of the light
composition. Devices such as scrims, gobos, snoots,source. Glare, such as observed on the surface of a
grid spots, and barn doors, are commonly used tobody of water, is a polarized direct reflection. Unlike
partially block, direct, or otherwise control the relativedirect reflection however, glare reflection always has
light intensities within a composition.a lower intensity than the light source producing it.
Another property of light of great importance to theGlare reflection may be controlled or eliminated by
portrait photographer is the light's color temperature.using a polarizing filter. Diffuse reflections occur when
Pure white light is the result of an equally balancedlight from a source is reflected equally in all directions
mixture of the three primary colors: red, green, andby the surface it strikes. In theory, diffuse reflections
blue. In different lighting conditions (e.g. cloudy versusare the same intensity no matter what angle they
full sun), the proportions of the color mixture mayare viewed from. The intensity of a diffuse reflection
vary. Normally, the human brain automaticallyincreases as the light source is moved closer to the
compensates for this, and you do not notice thesubject. The Inverse Square Law says that the
difference as you leave one lighting condition andintensity of the diffuse reflected light is inversely
enter another. Film can not make this same automaticproportional to the square of the distance between
compensation. Therefore, differences in colorthe light source and the subject. This implies, a light
temperature must be manually adjusted for by thesource at any given distance from the subject will
photographer. Color temperature of various lightlight the subject with an intensity that is four times
conditions is commonly stated in degrees Kelvin.greater than the same light source moved to twice
There are three standard color temperature ratedthe distance from the subject.
films commonly used by photographers. "Daylight" filmAn understanding of the behavior of light is a
is designed to be exposed by 5500K light, andprerequisite to understanding how to control the light.
"indoor" film is designed to be exposed by 3400KWe see that light can act on any subject it strikes.
light, or 3200K light for professional "indoor" film. For aIntensity or brightness, color temperature, and
greater degree of control over the white balancecontrast are the three properties that are of most
when using film, color correction filters are used. Mostconcern to the portrait photographer. Any subject
if not all digital SLR cameras have a white balancealso acts on light that strikes it, either through
adjustment to electronically compensate for changingrefraction, reflection, absorption, or some combination
color temperatures encountered in various lightof the three. In portrait photography, light is
conditions. In digital photography, when shooting incontrolled to achieve optimum overall exposure of a
RAW format, the color temperature can easily becomposition, to develop of specular highlights, to
corrected in Photoshop.reveal and enhance textures, forms and color
A third property of light that is very important to thesaturation, and to build a three dimensional
portrait photographer is contrast. A light source hasperspective. In Part 2 of this article, the fundamentals
high contrast if its rays all strike the subject atof controlling the overall exposure of a composition
approximately the same angle. A light source that isusing the camera are discussed. Until then, good day
diffuse has low contrast, because its rays strike theand happy clicking.