ETECH Test 3

What is the layered approach in lighting design and its advantages?

A strategy that combines multiple types of lighting to create a balanced, flexible, and visually appealing environment. Types of lighting utilized are normally: ambient, task, accent, and decorative lighting. Play of brilliance, focal glow, and ambient luminescence.

Considered aspects in determining the CU (coefficient of utilization) of a fixture

Room cavity ratio, surface reflectance, and lamp luminaire characteristics.

Which light source is most likely represented by a spectral distribution curve that rises and falls in the middle?

High pressure sodium lamp (yellow and orange).

The visible portion of the electromagnetic wave spectrum lies between what values?

380 - 780 nanometers.

The LED lamp is typically fitted with heat sink because?

The electric junction cannot be allowed to excessively overheat.

Which of the three lamps has the highest luminous efficacy?

LED (lm/watts).

Give 3 specific reasons that privilege the use of LED lamps in comparison to fluorescent lamps.

Energy efficient, long life-span, and it doesn’t put off heat.

What is the VCP (visual comfort probability)?

An index that indicates the potential effect of glare, with the minimum acceptable value being 70%.

What is the difference between maintained and initial illuminance for the lumen method?

Initial is the luminance right at installation, and maintained is the luminance right before burn out (end of life-span, usually 20-40% of original usage).

What is CT (color temperature)?

A scale to measure color appearance of light expressed in degrees Kelvin. Higher is cooler and lower is warmer.

What are good references in specifying which light source to use in a clothing store display?

A CRI and CCT of a map.

If a red car is parked under high pressure sodium lamps (yellow/orange), what color is perceived?

A brownish/red hue.

In designing a store dedicated to carpet displays at floor level, what would the height of the surface be considered equal to?

A work plane height of 0.

How does indirect light show on a photometric web?

90-100% up, 0-10% down.

How does direct-indirect light show on a photometric web?

Around 40% upwards and 60% downwards.

The sizing of lamps (from the diameter) is done in what ratio?

1/8ths of an inch.

What lamp requires a driver instead of a ballast?

LED lamps (also need heat sink).

What lamp doesn’t require a driver or a ballast?

Incandescent lamps.

What are candelas?

The intensity of light in a particular direction expressed in units.

Usually ceilings have bright surfaces, but what’s an example where a dark ceiling is better?

A theater because this ceiling will minimize light reflection and glare, which is crucial for maintaining optimal visual contrast on the screen. It also helps to create an immersive environment by absorbing ambient light, allowing the audience to focus on the performance/projection. It also improves the overall atmosphere and mood, supporting the intended dramatic or visual experience.

How do you find the luminous intensity of light on a photometric web drawing?

Follow the degree line/angle till it hits the light wave on the graph, then follow that line to the values on the left of the graph.

What is efficacy?

How efficiently a light source produces visible light in lumens/watts.

What is a driver?

LEDs use these in place of ballasts to regulate and convert power.

What unit is luminance measured in?

Candela per square meter (cd/m²)

What unit is illuminance measured in?

Lux or lumen per square meter (lux/m² or lm/²)

What is the unit for luminous intensity?

Candelas (cd).

What unit is used for luminous flux?

Lumens (lm).

What are cones?

They represent color perception.

What are rods?

They perceive the values of dark/grey colors.

What is CCT (correlated color temperature)?

A more general perceived color of light source not specific to black body radiators. How it appears and makes you feel.

What is the CRI (color rendering index)?

It measures how accurately a light source displays the color of an object compared to natural light measured from 1-100. Where anything 80 and above is considered acceptable.

What colors make white light?

Red, green, and blue.

What percentages of light distribution makes up direct, direct-indirect, semi-direct, and semi-indirect?

10-90%, 60-40%, 40-60%, and 60-90 - 40-10%.

What is the LLF (light loss factor)?

It quantifies the reduction in illuminance (light output) of a lighting system over time due to various factors like lamp lumen depreciation, luminaire dirt buildup, and room surface depreciation.

How do you find the brightness of a surface?

Brightness is illuminance. Illuminance = intensity (lumens) divided by the distance (feet) squared.

What color is CT at 3600 K?

A warm/neutral hue is perceived a this value.

What height is and indirect feature best hung from a ceiling?

24” for even illumination and reflection.

What percentage of heat does a incandescent lamp generate per watt of power used?

About 77%.

Is the luminous intensity dependent on the distance from a point source?

No, luminous intensity is an independent value that doesn’t change based on perceptive distances.

What is reflectance?

The ratio of the light reflected by a body to the incident light.

What is light?

Radiant energy evaluated by its capacity to produce a visual sensation. The time rate of the flow of light. The total light output from a source.

What is luminous intensity?

Solid angular flux density in the direction considered. The brightness and direction.

What is illuminance?

Density of luminous flux incident upon a surface. Brightness.

What is luminance?

The luminous intensity of any surface in a given direction per unit of projected area of the surface viewed from that direction.

What is accommodation?

The focusing activity of the lens of the eye.

What is adaptation?

Adjustment of the iris and change in response of the cells on the retina.

What is brightness?

A sensation.

What 3 primary factors must be considered to ensure proper visual acuity?

Good illumination, contrast, and glare control.

What are the 3 layers of illumination?

Ambient, task, and accent lighting.

What is the point-by-point method?

It calculates light density at specific points. E(fc) = [intensity (cd) divided by distance (feet) squared] times costheta. For finding the horizontal illuminance (regular) use cosine and for vertical use sine.

What’s the difference between spot light and flood light?

Spot light is 15-30 degrees, and flood light is 30-120 (usually 60) degrees.

What are the typical reflectances at a floor, wall, and ceiling?

20%, 50%, and 80%.

What is and IES file?

It contains detailed information about how a light source distributes light and it’s mainly used for light design and analysis.

How do you determine the number of fixtures needed to illuminate a space?

Using the lumen method. # = [E (fc) times the area] divided by [CU times LLF times RCR (N) times L (lumens per lamp).