Lighting is an extensive subject and can be quite technical. The key to answering lighting questions correctly on each exam section —IDFX, IDPX, or PRAC— is understanding the different lighting systems.
Know why one type of lighting may be better than another for a specific purpose, one environment, or for certain people using a space.
Lighting system types
Low-voltage fixtures require a transformer to “step down” the voltage from 120 to 12 volts. But they also tend to be smaller in size and have more control of the beam spread.
Low voltage lighting can include incandescents like MR16s (usually a halogen or incandescent) and LEDs.
Different light systems direct or throw light into space in different patterns or directions. The best choice is based upon whether the purpose of the lighting is decorative, task, or fill/ambient lighting.
You'll need to be familiar with each type listed below and the scenarios where each is appropriate to enhance the functions of the space.
- General diffuse
Light source types
You'll need to be familiar with how each type of lamping (bulb type) is designated, color rendering, cost, efficiency, and pros/cons of these light source types:
- High-intensity discharge (HID)
Brightness and Contrast
Think of each type of lighting system as a layer, and start with the functional or decorative lighting. Then fill in between with a different lighting system. For example, if the selected task and decorative lighting are direct, indirect lighting can balance and fill in.
The degree of contrast and the type of system you choose will depend upon the purpose of the space: is it for work or relaxation?
What type of activities will happen in the space? The amount of lighting or brightness should support the activity. Consider the pattern or direction/distribution of light and the surface — will the light be absorbed or reflect?
What are the sensory considerations? For example, should the “mood” be more dramatic or soft and intimate? Will the space's occupants have any special needs due to age, vision ability, or other psychological conditions?
For example, someone who is 60-80 years old may need three or four times as much light as a twenty-year-old for the same task. Older eyes are also more sensitive to glare.
Lighting color temperature
Light has an inherent color, and it can significantly affect how an object or space appears.
Light sources have a rating in degrees Kelvin, called the color temperature, based on its predominant wavelength color, ranging from about 3,600K to 9,000K.
Natural daylight is very blue or cool and is at the top of the scale at 9,000 K. Meanwhile, HID's are very orange and at the bottom of the scale. Fluorescents and incandescents are in between, and you should know the general Kelvin ratings associated with each.
Remember, the lower the color temperature number, the warmer the light will appear.
Daylighting means using natural light through windows, skylights, and light shelves as much as possible. Besides saving money and power resources, it also benefits the psychological health of the building occupants.
The most natural light will change throughout the day. First, the lighting for the daytime will be brighter and bluer. Then the color will become progressively warmer in yellow to orange to red tones with less intensity in the evening.
Lighting Terms and Definitions
Some lighting terms you should be familiar with include: lumens, candlepower, brightness, illumination, direct glare, reflected glare, veiling reflection, contrast, reflector, and coefficient of utilization.