A Photo Teacher |

Nature of Light and Artificial Light

Posted in Lecture Materials by Paul Turounet on September 24, 2007

As photography utilizes light-sensitive materials, whether analog or digital, the photograph needs light (and the lack of light) to reveal (and obscure) its visual sensibilities and concerns of content. The presence of light and its level of intensity serve as visual guides in seeing what is in a photograph as well as affecting the feeling being suggested.

The direction of the lighting is important because it will determine what is revealed and what is concealed and left in shadows. Light shapes the subject being photographed, emphasizing or diminishing description, texture and volume. Consider the following lighting circumstances:

© Walker Evans (left) and Paul Outerbridge (right)

Front lighting comes from behind the camera toward the subject. The front of the subject is evenly lit with minimal shadows visible, i.e. Walker Evans.

Side lighting comes toward the side of the subject and camera. Shadows are prominent and cast at the side of the subject, emphasizing shape, texture and volume, i.e. Paul Outerbridge.

© Josef Sudek (left) and Zeke Berman (right)

Diffused lighting scatters onto the subject from many directions. Shadows are relatively light and the subject seems surrounded by light. Directional-diffused lighting combines the qualities of direct light and diffused light, allowing for shadows to be visible, but not as prominent, i.e. Josef Sudek. Fully diffused lighting provides an even, soft illumination.

Back lighting comes toward the camera from behind the subject. Shadows are cast toward the camera and are prominent with the front of the subject in shadow. Back lighting can make translucent objects seem to glow as well as create a strong contrast between light and dark areas, i.e. Zeke Berman.

Artificial Light

In using artificial light, the same considerations and properties exist as with natural light. The direction of the light and the level of the lights luminance will dictate the nature of how light will reveal what is being photographed, the thing itself, as well as the details. However, unlike a natural light source, artificial light offers greater control in producing the desired effect. For additional information, you can reference Lighting in Photography in Photography by London (et al).

The size of the light source, the level of luminance and direction of the light, and the physical distance of the light from the subject all function as means of controlling artificial light. While a larger light source will generally provide a wider and softer quality of light, a smaller light source, such as a spotlight, will focus the light sharply producing bright highlights and distinct shadows. The closer the light source is to the object, the softer and more diffused the lighting will be. Moving the light source further away will create more distinct shadowing.

Types of Light Meters

Reflected-Light Meter – Can be either hand-held or built into a camera. Aim sensor at subject to get a reading of the light reflected from a subject.

Incident Light Meter – Hand-held, faced toward the camera from the position of the subject, measuring light falling on subject. Can also be used as a reflective light meter.

Spot Meter – Either hand-held or built into a camera, measures reflected light from small part of subject.

Flash Meter – Measures the output of light from an electronic light, such as a flash or strobe.

Light Metering Techniques with Incident Light Meter

Take an exposure reading with an incident light meter and select the appropriate shutter speed / aperture combination.

a. Set ISO/ASA of film being used.

b. Hold light meter in front of scene with the sphere pointed at the camera.

c. Depress center button.

d. Needle will move to a reading.

e. The reading is measured on the foot-candle scale.

Depending on the lighting conditions, there are two settings that can be utilized – the Red Arrow setting (when the High Slide is inserted in the slot below the sphere) is used outdoors in bright light and the Black Arrow setting (High Slide is removed) is used in lower light circumstances.

f. Move dial to Black Arrow setting when High Slide is not used so the number lines up with the corresponding number on scale.

or

g. Move dial to Red Arrow setting when High Slide is used so the number lines up with the corresponding number on scale.

h. Shutter speed scale

i. Aperture scale

Types of Artificial Light

Photofloods are similar to household lights, but produce more light than a conventional bulb of the same wattage. Referred to as “hot lights,” photofloods produce a light of 3200°K color temperature (tungsten balanced) and have a relatively short life. Quartz-halogen bulbs contain a gas that prolongs their use as well as maintain a more consistent color temperature, and consequently are more expensive than photoflood bulbs.

Stobes and camera-mounted flashes provide tremendous options in using artificial light both in the studio and natural settings. Because the burst of light is short, stop action of a subject can be achieved. In addition, both strobes and flash units provide for a consistent color temperature.

The light of photofloods and strobes can be controlled through the use of such devices as a reflector, snoot, and barn doors. The reflector concentrates the light and points it in a direction. Like the reflector, the snoot attaches on the front of the lamp and narrows the beam of light. Barn doors, both as pairs or two pairs, can be folded at various angles to control the direction of the light. The level of luminance can be further controlled through the use of diffusion screens, and flat reflectors.

One Light – The Main Light

When setting-up to use artificial lights, it will be necessary to begin setting up the main light. Also referred as the key light, the main light is the light source that casts the dominant set of shadows. The position of the main light will affect the appearance of texture and volume. Consider the following possibilities when setting-up the main light:

1. Front lighting places the light source directly in front of the subject near the lens axis, flattening volume and minimizing texture.

2. Referred as “hatchet” lighting, side lighting is placed directly to the side of the subject and splits the subject in half, creating strong shadows and emphasizing texture.

3. High side lighting, roughly at a 45° angle from the side and above, models the object into a three-dimensional form. This type of lighting is a popular method for portraiture as well as modeling an object.

4. With top lighting, the light source is directly above the subject, casting strong shadows downward.

5. Under lighting casts light from a low angle. Because it is not normally how light illuminates an object, this type of lighting can further suggest mystery and drama.

6. Utilizing back lighting can emphasize shape and form.

The Second Light – Fill Light

While the main light, key light, is the primary light source to provide a modeling of the subject or object, most often two light sources are utilized for even greater control of shadow description. This second light source, the fill light, is generally a diffused light source that adds light in varying degrees to a shadow(s). Since a single light source (one light) set-up can create considerable contrast, the fill light can open-up the shadow detail and description.

In setting up the fill light, it is generally placed on the side of the lens opposite that of the main light and close to the camera at lens height. In this position, the fill light will produce no visible shadow patterns of its own.

The fill light can be as simple as a flat reflector, either a matte white board for a softer diffused quality of light or with a reflective material wrapped around the board for a more brilliant quality of light.

When using a photoflood or strobe as a fill light, it will be necessary to use a lower output than the main light. This can be accomplished by placing the fill light farther away from the subject or object, by utilizing a lower level of luminance, or by using diffusion screens in front of the fill light source.

Fill Light Ratio

The difference between the lit side of a subject or object (main light) and the shadow side (fill light) can be understood as a ratio. As a general rule, the higher the ratio, the greater the contrast. Doubling the ratio is equivalent to a one-stop difference between the highlights and shadows.

With a 1:1 Ratio, there is no discernible difference between the lit side of the subject or object and the shadow side. A 2:1 Ratio provides a full-stop difference or twice as much light on the lit side than on the shadow side. The 4:1 Ratio provides a two-stop difference and generally, portraits are made with a 3:1 or 4:1 Ratio. With the 8:1 Ratio, a three-stop difference, it is likely detail and description will be lost in the shadows.

Reflective Objects

In photographing objects with reflective or glossy surfaces, it may necessary to utilize a tenting technique to minimize unwanted reflections. The tenting is created around the object by utilizing plain surfaces such as translucent paper.

Translucent Objects

An additional consideration may include lighting translucent objects from behind or by lighting up the background. Frontal illumination usually will cause problematic reflections.

Click on the Adobe Acrobat PDF file to download: Nature of Light and Artificial Light.pdf

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