CHINFOINST 1510.1 CHINFO Media and Communication Study Guide, Enclosure 9

Question 1

Theory of Light

Answer 1

Light is a form of energy that radiates from a source. This source can be anything from the Sun to a simple lightbulb. Regardless of the source, light behaves both as separate energy particles and electromagnetic waves. (Zettl 19) Those electromagnetic waves make up the foundation of what is known as the electromagnetic spectrum, or in a more narrow sense, the spectrum of visible light.

Question 2

Wavelength

Answer 2

The distance from one peak to another in a wave of light. Measured in nanometeres (nm).

Question 3

Visible Light Spectrum

Answer 3

400-700 nm

Question 4

Frequency

Answer 4

The measurement of how many times a wave of light passes a given point in one second. Typically this measurement is expressed in the SI unit of hertz or Hz.

Question 5

Hz

Answer 5

1 Hz is equal to 1 cycle per second, so for example a wheel rotating at 1 revolution per second, or 60 revolutions per minute (RPM) can also be described as having a frequency of 1 Hz.

Question 6

Law of Conservation of Energy

Answer 6

In a closed system, energy is neither created nor destroyed, it is converted or transferred from one form to another. What this means for the photographer or videographer is that light is not created by your lighting instrument, it is merely converted from electrical energy to light. When you block light with a flag or modify it with a gel, it is not destroyed, just reflected or converted into thermal energy (heat).

Question 7

Speed of Light

Answer 7

The speed of light is variable depending on the properties of the surface that the light is passing through. If light is passing through glass, for instance, it will slow down, and the wavelength will shorten but the frequency will remain the same. Speed = Wavelength X Frequency or Wavelength = Speed/Frequency

Question 8

Principles of Light Speed

Answer 8

Light will always travel in a straight line in a given medium (material) and the speed of light travelling through the same material will be constant.

Question 9

Reflection

Answer 9

Reflection of light occurs when light from a source bounces off of a surface.

Question 10

Principles of Reflection

Answer 10

The reflected light will always reflect in the same angle as it reached the surface. So, if light strikes a surface at an angle of 45 degrees, it will be reflected back at 45 degrees.

Question 11

Specular Reflection

Answer 11

When the surface that the light is reflecting on is smooth, the resultant reflection will be orderly, or specular. Common examples of specular reflections would be mirrors or highly polished smooth metal.

Question 12

Diffused Reflection

Answer 12

This is a direct result of light from the light source reflecting at their complementary angles off of each of the imperfections in the surface.

Question 13

Transmission

Answer 13

Depending on the physical properties of the material that the light is hitting, not all of it may be reflected at a complementary angle to its source. Some of that light may pass through the object and emerge on the other side. Objects displaying these characteristics are said to be translucent, or clear depending on the wavelengths of light that they will allow to transit. There are many interactions that can take place within a medium that determines which light is transmitted, reflected or absorbed.

Question 14

Absorption

Answer 14

The light that is reflected or absorbed by the opaque object will determine the color that the object appears to the naked eye.

Question 15

Refraction

Answer 15

As light is transmitted through a surface, it’s speed changes, frequency remains constant, but wavelength changes. As speed changed, direction will change. Direction change is refraction.

Question 16

Dispersion

Answer 16

Different wavelengths of light refract at different angles depending on the material that they pass through. This separation of light is collectively known as dispersion. White light passing through prism (Pink Floyd example).

Question 17

Diffraction

Answer 17

When light is shined on an opaque edge, the light will bend slightly. As the light bends, it will separate into the wavelengths that make up the light.

Question 18

Polarization

Answer 18

Occurs when this light passes through a filter that restricts its movement to only one axis.

Question 19

Color Temperature

Answer 19

Kelvin temperature is a function of heat applied to a black body. It is important to note that traditional color theory says that red colors are warm and blue derivatives are cool, when describing color Kelvin temperature, this is not the case. For Kelvin temperature, red colors have a lower value, while blue colors have a higher value.

Question 20

Attached Shadows

Answer 20

Are always part of the actual object and will remain no matter how you move the object as long as the light source does not move. A good example of an attached shadow is a sphere where the side facing away from the light source remains in shadow. No matter how you move the object, there will be a shadow on the side that faces away from the light.

Question 21

Cast Shadows

Answer 21

Are created when light is blocked by an opaque surface and the shadow falls on a surface other than the object blocking the light. Cast shadows can be object connected, object disconnected or object independent.

Question 22

Inverse Square Law

Answer 22

The intensity of illumination is inversely proportional to the square of the distance between the light and the subject. Simply put, a light that is moved twice as far from the subject, only a quarter of the original light will be on the subject.

Question 23

Falloff

Answer 23

The tendency of light and shadow to fade in a gradual manner.

Question 24

Fast Falloff

Answer 24

The highlight area is very bright and the shadow is dark and rich.

Question 25

Slow Falloff

Answer 25

Less contrast between shadow and light.

Question 26

Flat Lighting

Answer 26

Lighting ratio of 1:1 because both the main and fill lights would be striking the subject at the same intensity.

Question 27

Outer Orientation

Answer 27

The ability of light to tell us the shape of an object, its texture, and its position in time.

Question 28

Inner Orientation

Answer 28

The ability of light and shadow to convey a sense of mood and atmosphere.

Question 29

Triangle (3 Point) Lighting

Answer 29

Main light, fill light, hair light.

Question 30

Main Light

Answer 30

As its name would imply, the Main Light is the primary source of illumination for your subject. This light is what is going to determine the overall exposure level and the intensity of the other lights in the scene. The Main Light may be positioned on either side of the subject and may illuminate the side of the face turned towards or away from the camera, broadside and short side lighting respectively.

Question 31

Fill Light

Answer 31

The Fill Light works in conjunction with the Main Light to soften, or fill in, the shadows created by the Main Light. These shadows define the depth of the subject and the intensity, or darkness, of these shadows is controlled by the intensity of the Fill Light. The Fill Light is the light that is going to determine the lighting ratio 1:1, 2:1 4:1 etc… of a scene. Traditionally, the Fill Light is placed opposite the Main Light and strikes the subject at approximately the same angle as the Main Light.

Question 32

Backlight/Hair Light

Answer 32

Now that the tront of the subject is illuminated, it is time to pay attention to how the subject interacts with the background of the scene. The Backlight or Hair Light provides a sense of separation between the subject and the background. Essentially, a Backlight creates a small rim of light on the fill side of the subject to prevent the subject from disappearing into the background.

Question 33

Chiaroscuro Lighting

Answer 33

Features highly directional lighting that highlights certain intentional aspects of the scene coupled with fast falloff shadows.

Question 34

Answer 34

Chiaroscuro Lighting

Question 35

Aesthetic Functions

Answer 35

Organic, directional, spatial, compositional, thematic, emotional.

Question 36

Organic Lighting

Answer 36

Light that is added to a scene should look as though it has a purpose for being there. Take the Honthorst painting above for instance, it would seem out of place for the artist to illuminate the scene from above when there is clearly a burning candle on the table. The same holds true when photographers and videographers light scenes. If a subject is sitting near a window during daytime, illuminate them on the side that the window is on.

Question 37

Directional Lighting

Answer 37

Light can be used to highlight portions of the image that the photographer or videographer wish to highlight. This is used to take the viewer on a visual journey through the image and detail important items.

Question 38

Spatial Lighting

Answer 38

Light areas and dark areas of a frame should be spaced out in such a way as to allow for a sense of balance to be present within the scene. Images that are too skewed light or dark may not have visual interest, or worse may distract from the message that the shooter is intending to convey.

Question 39

Thematic Lighting

Answer 39

The way that a scene is lit should serve to help in telling the story that the photographer or videographer wishes to tell. If the overarching theme of the piece is death for instance, the photographer should emphasise the shadows of the scene. Likewise, if the scene is about birth or life, High-Key lighting may be in order.

Question 40

Emotional Lighting

Answer 40

Emotional and Thematic functions are closely tied with one another. The emotional function of light is to impact our feelings regardless of subject matter.

Question 41

Flat Lighting

Answer 41

The exact opposite of Chiaroscuro Lighting. Instead of creating dramatic interplays between highlight and shadow, the function of Flat Lighting is to eliminate shadow. Typically, Flat Lighting does not have an obvious light source. Light wraps around the subject casting translucent and almost invisible attached and cast shadows. In short, nothing is lost in shadow because shadows are not present in the scene.

Question 42

Answer 42

Flat Lighting

Question 43

Silhouette Lighting

Answer 43

Emphasizes contour over volume or texture. The key to effective Silhouette lighting is lighting and exposing for the background of the image.

Question 44

Front Lighting

Answer 44

Illuminating a subject by a single light placed directly in front of the subject. The light source is placed as close to the axis of the lens as possible to reduce the distance that shadows extend from the object that cast it. This lighting is traditionally very flat in nature because the subject is looking directly into the light thus light is cast on both sides of their face evenly. It also serves to minimize texture because no light is hitting the subject from the side. Falloff from light to shadow will depend on the size of the light source and the extent that it is diffused

Question 45

Side Lighting

Answer 45

Serves to emphasise facial features and textures, such as that of skin. If a subject is facing the camera, side lighting will appear as though the subject has a line demarking light from shadow down the center of their face.

Question 46

Back Lighting

Answer 46

Used to separate a subject from the background.

Question 47

Answer 47

Side Lighting

Question 48

Existing Light

Answer 48

Anything that creates light can be used in a photograph.

Question 49

Flourescent Lighting

Answer 49

Gas lamps that contain mercury vapors that create light when electricity is passed through them.

Question 50

Factors That Affect Exposure When Using Flash

Answer 50

Shutter speed, aperture, distance, sensitivity, flash compensation.

Question 51

Flash Syncronization Speed

Answer 51

Camera will limit max shutter speed to avoid the shutter being present in the image.

Question 52

TTL Flash

Answer 52

Through the lens, an automatic flash control that uses the light passing through the lens of the camera to turn off the flash when the camera records a correct exposure. As a rule, TTL flash modes will only work with direct flash and only with the flash head locked in the down position.

Question 53

Automatic Flash

Answer 53

A setting where the camera measures the light that is falling on the scene and automatically fires the flash in low light scenarios.

Question 54

Manual Flash

Answer 54

A mode where the photographer takes complete control over the the flash unit. This mode allows the most aesthetic control but requires the photographer to know how to manipulate the camera’s exposure controls.

Question 55

Slow Sync Flash

Answer 55

Couples slow shutter speed to emphasise motion while using flash to freeze action and retain detail.

Question 56

Answer 56

Slow Sync Flash

Question 57

Rear Curtain Flash

Answer 57

Fires the flash just before the second curtain covers up the sensor ending the exposure. The resultant image has motion trails that extend behind the subject. This typically appears more natural and less jarring than front curtain sync.

Question 58

Fill Flash

Answer 58

The use of artificial light to supplement ambient light and add light to shadows when subjects are backlit, in shadow or illuminated by high-contrast lighting. In extreme cases, fill flash can be used to match the apparent intensity of the sun in a backlit scene thus rendering a natural looking exposure. This technique used to be referred to as synchro-sun flash.

Question 59

Red Eye Reduction Flash

Answer 59

When a flash is attached to a camera and is positioned close to the axis of the lens, the resultant image may exhibit what is known as red eye. This is as a result of light from the flash bouncing off of the subject’s retina and back into the camera. The simplest solution for reducing or eliminating red eye is to remove the flash from the axis of the lens. Some cameras and flash units have a built-in red eye reduction feature which shines a brief burst of light at the subject before the image is exposed. This serves to contract the subject’s pupils and reduce the window that light has to enter the eye and cause red eye.

Question 60

Off Camera Flash

Answer 60

Moving the flash unit allows a photographer to go from a frontlit portrait to sidelit, high-side lit, or even a back lit portrait. some of the most famous portraits were lit using only a single light source. Very few were taken with a flash attached to the photographer’s camera.

Question 61

Off Camera Flash Using Multiple Synchronization

Answer 61

Flashes can be grouped together and fired simultaneously so that they can mimic much larger studio strobes. Finally, modern flash systems allow the photographer to change the settings on each group of flashes from the master unit attached to the camera, thus giving the photographer quick and easy control over their flash units.

Question 62

Bounce Flash

Answer 62

Light is emitted from a flash unit, hits a surface and is then directed onto the subject. This allows photographers to drastically change the direction that their light hits their subject with minimal effort.

Question 63

Diffuser

Answer 63

When a focused beam of light hits a material that scatters light, it is diffused. A diffuser is a material that scatters and softens light. This diffused light creates a slow falloff in shadows and causes light to “wrap” around objects. Any object that softens light can act as a diffuser, but some of the most common are diffusion cloth, cheese cloth, and frosted plastic. Photographers must remember that diffused light, just like bounced light will lose its intensity and must be compensated for.

Question 64

Direct Flash

Answer 64

Flash pointed directly at the subject. Direct flash only deals with the direction that the light hits the subject, not the quality of light i.e. either diffused or undiffused.

Question 65

Painting With Light

Answer 65

A photographic technique where a photographer exposes a long shutter speed image while physically and intentionally moving a light source through the frame.

Question 66

Answer 66

Painting With Light

Question 67

Photography

Answer 67

Photography is the process of producing images by the reaction of radiant energy, particularly light on a sensitive surface