light and acoustics, interior design

1. LIGHTING & ACOUSTICS

2. INTRODUCTION
• The simplest definition of light is “visually perceived radiant energy". “Visible”
light is just a small segment of the electromagnetic spectrum— a broad range of
radiant energy which also includes X-rays, ultraviolet and infrared energy, micro-
waves and radio waves.
• As visually perceived radiant energy, light powers the mechanism of sight. It is
light, reflected from objects to our eyes, that allows us to see.
• Of all our senses, sight is the most dominant, controlling and defining how people
perceive the world. And yet it’s impossible to prove that any two people see a
given object in exactly the same way.
• In fact, it often seems that visual perception—an individual’s response to light—is
extremely subjective. This makes it difficult to define and measure specific
attributes of light.
• Furthermore, changes in light can change people’s perceptions.
• A dark alley, for example, provokes an entirely different reaction than one that is
brightly lit. Lighting, therefore, can have a profound effect on people’s emotions
and how they respond to an environment.

4. LIGHTING & VISION
• The sun, stars & electric lamps are visible to us because of the light they generate.
• Most of what we see, however, it is visible because of the light that is reflected from the
surface of objects.
• Our ability to see well- that is, to discern shape, color and texture and to differentiate
one object from another-is affected not oly by the amount of light available for
illumination but also by the following factors:
• Brightness
• Contrast
• Glare
• Diffusion
• Color

5. BRIGHTNESS
• Brightness is an attribute of visual perception in which a source appears to be
radiating or reflecting light.
• In other words, brightness is the perception elicited by the luminance of a visual
target. This is a subjective attribute/property of an object being observed.
• brightness, in physics, the subjective visual sensation related to the intensity of
light emanating from a surface or from a point source.
•Even though these objects may be uniformly illuminated, their surfaces differ in brightness according t
their
•Color
•Value
•Texture
•Ability to reflect light

6. • Harmonious distribution of brightness is important for sharpness of vision and
sensitivity to contrast, contrast being relatively small differences in brightness.
• Setting the brightness too low can again cause strain, decrease the visual
stimulation and therefore also work performance.
• Darker surfaces in the room can work against the harmonious distribution of
brightness and can cause feelings of oppression and anxiety.
• Brightness = illumination x reflectance
Contrast in brightness aids perception of shape & form

7. CONTRAST
• Contrast is the difference in luminance and/or color that makes an object (or its
representation in an image or display) distinguishable.
• In visual perception of the real world, contrast is determined by the difference in
the color and brightness of the object and other objects within the same field of
view.
• The maximum contrastof an image is the contrast ratio or dynamic range.
• Contrast is also the difference between the color or shading of the printed
material on a document and the background on which it is printed, for example
in optical character recognition.

8. Surrounding area (3) should range from 1/5 to 5 times the brightness
of the task area (1)
3:1 is the maximum recommended brightness ratio between the
visual task area and its immediate background (2)

9. Contrast using colors

10. GLARE
• Glare is difficulty seeing in the presence of bright light such as direct or
reflected sunlight or artificial light such as car headlamps at night. Because of this,
some cars include mirrors with automatic anti-glare functions.
• Glare is caused by a significant ratio of luminance between the task (that which is
being looked at) and the glare source. Factors such as the angle between the task
and the glare source and eye adaptation have significant impacts on the
experience of glare.

12. SOLUTIONS FOR GLARE
Locate light fixtures out of the direct
glare zone
Reduce the brightness ratio btw the
light source & its background

13. • Exterior window
shading strategies
to avoid glare

14. • Use well sheilded or baffled fixtures that
minimize direct view of bulbs or lamps.

15. DIFFUSION
Light diffusion
• Light diffusion (how light is spread) can significantly
decrease dazzle and glare from the different
surfaces and objects in a room.
• The more diffusely and evenly the light is spread the
better dazzle and glare are prevented.
• Light diffusion can be defined as the ratio of the
diffused reflected light to the totally reflected light.
• 1. Reflection from a bright polished metal surface or
a mirror.
• 2. Reflection from an ordinary painted surface
causes glare at certain angles.
• 3. Diffused reflection from Ecophon
Akutex™ surfaces prevents glare and dazzle.

16. • Diffused illumination reduces
contrast & shadows.
• Concentrated source of light,
incandescent downlight, produces a
directional light with little diffusion.
This enhances the perception of
shape, form surface texture.
• Diffused light is useful for general
vision.
• Can be used to provide visual
accents, brightness variation.

17. • Examples of diffused
lighting used in interiors.

18. COLOR
• Color and Light
We tend to think of objects as having fixed colors—an apple, for example, is red.
• In reality, an object’s appearance results from the way it reflects the particular light
that is falling on it.
• Under white light, the apple appears red because it tends to reflect light in the red
portion of the spectrum and absorb light of other wavelengths.
• If a filter is used to remove red from the light source, the apple reflects very little light
and appears black.
• The fact that the color makeup of light can change, means that shifts can occur in the
color appearance of objects illuminated by it.

19. • All Light Is Not the Same
Direct sunlight at noontime is an almost perfectly balanced
light source—it contains all colors in nearly equal quantities.
• But daylight does experience color shifts. The color
appearance of objects changes dramatically in early morning
or in the shade.
• Electric light sources can also exhibit variations in color
makeup. Incandescent lamps tend to produce more red and
yellow light than green and blue, and appear to be “warm” in
color.
• Because of the way incandescent light is produced, little can
be done to manipulate its color characteristics.
• With fluorescent and high intensity discharge lighting, this
latest technology makes it possible to manipulate the color
makeup of a given light source.

20. • White Light and Bright Colors
Generally speaking, whiter light (comprised of equal amounts of all colors) makes
colors appear more natural and vibrant.
• However, some portions of the spectrum are more important to a light’s color
makeup than others. Red, blue and green—the primary colors of light—can be
combined to create almost any other color.
• This suggests that a light source containing balanced quantities of red, blue and
green light can provide excellent color appearance even if this light source is
deficient in other colors in the spectrum.

21. DAYLIGHTING
• The source of all daylight is the sun. its light is intense
but will vary with the time of the day, from season to
season and from place to place, it can also be diffused
by the cloud cover, haze, precipitation or any pollution
that may be present in the air.

22. • Daylighting is the practice of
placing windows or other
openings and reflective surfaces
so that during the day natural
light provides effective
internal lighting.
• Particular attention is given to
daylighting while designing a
building when the aim is to
maximize visual comfort or to
reduce energy use.
• Artificial lighting energy use can
be reduced by simply installing
fewer electric lights because
daylight is present, or by
dimming/switching electric lights
automatically in response to the
presence of daylight, a process
known as daylight harvesting

24. High window openings allow daylight to penetrate
more deeply into an interior space.
Locating window adjacent to perpendicular wall
maximizes light entering.

25. DAYLIGHTING EXAMPLES
• Bidirectional lighting – lighting from 2 directions raises
the level of diffused light in a space and reduces
posssibilty of glare.

26. • Provision of skylights
Tubular skylights
Flat & domes skylights