WIKI-2B

Properties and Quality of Light

Quality of Light

• Involves evaluating light from natural and artificial sources considering:
  • Hard light (specular).
  • Soft light (diffused).
  • Inherent color value.

The Color of Light

• Electromagnetic Radiation Spectrum: Includes a small visible light section.
• Visible Light Spectrum:
  • Varying wavelengths determine perceived color.
  • White light contains all wavelengths.
• Prism Effect:
  • Passing white light through a prism separates light waves into a rainbow.
  • ROY G BIV (Red, Orange, Yellow, Green, Blue, Indigo, Violet) helps remember the order.

Color Temperature

• Describes color values using the Kelvin Color Temperature Scale (K°).
• Color has a numerical value expressed in degrees Kelvin.

White Light

• RGB (Red, Green, Blue): Cameras reproduce colors by adding these values.
• Daylight:
  • Basis for natural color perception.
  • Typically measured at $5500 K°$.
  • Represented by the sun icon on camera white balance settings.
• Color Perception:
  • Result of light reflecting off a surface.
  • Under white light ($5500 K°$), a white sheet appears white.

Color Shifts

• Light Source Color: Every light source has its own color value (K°).
  • Ranges from warm tones (candlelight - $1000K$) to cool tones (shade - $10000K$).
• Impact on Photography:
  • Photographers must be aware of how a light's color value affects recorded colors.
  • A light source at $2800K$ (warmer) will make white appear orange/yellow.
• Brain vs. Camera:
  • Brains interpret colors based on experience.
  • Cameras record actual reflected light values.
• White Balance Correction:
  • To photograph a white sheet under $2800K$ light, adjust white balance from sun icon to light bulb icon.
  • Cameras with Kelvin options allow specific settings (e.g., $2800K$).
• Kelvin Options:
  • Cameras often range from $2200K$ to $10000K$ in $100°$ increments.
  • Offers 79 distinctive white balance options for accuracy.

Accurate Color

• Importance: Accurate color is crucial in commercial photography.
• Deliberate Color Shifts: Photographers may intentionally shift colors:
  • Warmer skin tones.
  • Cooler tones in snow scenes to represent cold.
  • Warmer tones in summer scenes to emphasize heat.
  • These shifts are part of a photographer's artistic expression.

Properties of Light

• Light's behavior follows physical laws.

Angle of Incidence

• Principle: The angle of incidence equals the angle of reflectance.
• Example:
  • A ball thrown at $45°$ to a wall bounces off at the same angle.
  • Light reflects similarly.
• Photography Application:
  • Flash reflected in a mirror follows this principle.
  • Normal: Line between camera and subject.
  • $0°$ angle of incidence: Light source directly behind the camera.
  • $45°$ angle of incidence: Light at $45°$ to the normal.
• Surface Reflectivity:
  • Glossy surfaces reflect more light than matte surfaces.
  • Reflected light takes on the color of the reflecting surface.

Size of the Light

• Determines hardness or softness, highlight size/intensity, and shadow transitions.
• Smaller Light Sources:
  • Create specular highlights.
  • Harder transition between highlight and shadow.
• Larger Light Sources:
  • Create diffused highlights.
  • Softer transition between highlight and shadow.
• Example:
  • Small portable flash creates specular highlights and abrupt transitions.
  • Softbox (large light source) creates diffused highlights and gradual transitions.

The Inverse Square Law

• Definition: "The intensity of the light on a subject is inversely proportional to the square of the distance of the subject from the light source."
• Equation:
  $Intensity \propto \frac{1}{Distance^2}$
• Doubling Distance: Lose two stops of light.
  • Example: F11 at 10 feet becomes F5.6 at 20 feet.
• Halving Distance: Gain two stops of light.
  • Example: F11 at 10 feet becomes F22 at 5 feet.
• The math looks like this: The distance is doubled (2X). The inverse of 2 is 1/2. $(1/2)^2=1/4$
• The output of the light at ten feet was F11. At twenty feet, it is now 1/4 (two stops) the intensity that it was at 10 feet.
• The math looks like this: Distance is cut in half (1/2X). The inverse of 1/2 is 2. $2^2 = 4$
• Now, at five feet, the light is 4X brighter (two stops) than it was at ten feet.

Depth of Light

• Describes the consistency of exposure and the rate of light falloff.
• Light Falloff:
  • Light falls off more rapidly at closer distances.
  • Light falls off less rapidly at further distances.
• Example: Lighting a Car:
  • Softbox 5 feet from the front: Light falls off quickly from front to rear.
  • Light at 15 feet from the front: Light falls off slower.
• Application: Useful when controlling how quickly the light falls off on the subject.

Quantity of Light

• Exposure: Based on the quantity of light on the subject and within the scene.
• Measurement: The quantity of light can be measured with a light meter.
• Considerations:
  • Best angle.
  • Impact of other light.
  • Exposure values of shadows.
  • Lighting intensity in the background.
  • Impact of including the sky.
• Actions:
  • Introduce additional lighting.
  • Block unwanted light.
  • Redirect light.
  • Introduce artificial main light.
  • Change scene.
• Exposure Basis:
  • Usually based on subject lighting.
  • Can be based on other elements (e.g., silhouette).
• Interpretation: Proper exposure is a mix of science and art.

Quality of Light

• Evaluation: Considers hard light (specular) vs. soft light (diffused), and the color of the light.
• Hard Lighting:
  • Direct sun creates sharply defined shadows.
  • Small light source relative to the subject.
• Soft Lighting:
  • Sunlight diffused by clouds converts hard light to a larger light source.

Soft, Diffused Lighting

• Overcast Sky: Acts as a large softbox to diffuse sunlight.
• Characteristics: Low contrast, lacking distinctive shadows.
• Ideal for Portrait: Most flattering for portraits.
• Open Shade: Provides best opportunities for soft, diffused light in outdoor portraits.

Studio Lighting

• North-Facing Window: Preferred studio choice as it avoids direct sunlight.
• Benefits: Offers soft diffused light throughout the day.

Lighting Design

Hard Light Sources

• Description: Harsh light from a small source, creating strong shadows and high contrast.
• Characteristics: Emphasizes texture and form and can be used to create drama or highlight facial features.
• Sources:
  • Portable flash.
  • Parabolic reflectors.
  • Bare studio lighting sources.
  • The sun (due to its distance).
• Distance: Even a softbox can become a hard light source if positioned too far from the subject.

Soft Light Sources

• Description: Diffused light sources which are generally soft because they are larger in size and used at close distances to the subject.
• Modification: An umbrella and softbox enlarge the light source by bouncing it.
• Impact of Distance: The closer the light source is to the subject, the softer the light/The further away the light source is from the subject, the harder the light becomes.
• Ideal Application: Softer light is generally considered to be more flattering to portrait subjects because it tends to hide wrinkles and blemishes. The larger the source, the softer the light, it is also often used in landscape photography because it has considerably less contrast than hard lighting.

Flat Lighting

• Description: Light that strikes the subject from the front or does not rake across to bring out texture.
• Examples:
  • Overcast day.
  • On-camera flash.
  • Subject facing the sun with the sun behind the camera.
• Applications:
  • Product photography.
  • Fashion photography (to diminish features and focus on clothing).

Light Tent

• Used to create very flat and shadowless lighting for product photography.
• Diminishes model's features to focus attention on clothing.