Lighting Lecture 1 on science Lighting.ppt
- 1. Architectural Sciences III (Light & Energy) ARCH4144 Addis Ababa science and Technology University College of Engineering Department Architecture
- 2. INTRODUCTION TO SCIENCE OF LIGHT
- 3. What is light? Light is defined as the electromagnetic radiation with wavelengths between 380 and 750 nm which is visible to the human eye.
- 4. Visible spectrum The visible spectrum is the band of the electromagnetic spectrum that is visible to the human eye. Electromagnetic radiation in this range of wavelengths is called visible light. The colors of the visible spectrum include red, orange, yellow, green, blue, indigo, and violet. The acronym ROYGBIV may be helpful in remembering the order of the colors that make up the visible spectrum. Violet has the shortest wavelength, at around 380 nanometers, and red has the longest wavelength, at around 700 nanometers.
- 6. The color of light : is determined by its spectrum or spectral composition. • Light of a particular wavelength is referred to as monochromatic. • The color of broad-band light depends on its spectral composition. • A continuous spectrum white light can be split by a prism into its components, which are perceived as colors. • Color theory of light distinguishes red, green and blue as the primary colors, and any color can be defined in terms of its redness, greenness and blueness.
- 7. It was Sir Isaac Newton(1642-1727) who made the first detailed observations of the composite nature of sunlight. By using a prism, Newton determined that sunlight was actually a mixture of many different wavelengths, each perceptually experienced as a different hue, when isolated.
- 8. Composite vs. Pure light Pure light: perceptually this is light which can be experienced as only one hue. It cannot be broken down into any further component hues. Theoretically, this is light of a single wavelength, which is very difficult to achieve. This monochromatic light is very rare occurrence as most light is composite light which is comprised of different wavelengths that can be isolated and broken down into separate colors. Composite light: light comprised of many different wavelengths, which if isolated would be perceptually experienced as different hues
- 9. Color of light Color Wavelength band (nm) • Red 780–630 • Orange 630–600 • Yellow 600–570 • Green/yellow 570–550 • Green 550–520 • Blue/green 520–500 • Blue 500–450 • Violet 450–380
- 10. Color vision is the ability to make discriminations based on the wavelength composition of the light independent of its intensity.
- 11. Components of color Hue: the perceptual pigmentation difference experience with varying wavelengths, this is what we are actually referring to when we use terms such as "green" or "blue." Brightness: refers to the intensity of the hue, varies in relation to the amplitude of the light. Saturation: refers to the degree of white light mixed in with the dominant wavelength. Perceptually experienced as the purity of the color. Color is comprised of three distinct components:
- 12. Surface colors comprehensive classification of surface colors. This distinguishes three attributes : 1. Hue 2. Value or lightness 3. Chroma or saturation
- 13. •Hue Qualitative, easily identified category of visual experience (Colloquially known as ‘color’; e.g. ‘red’, ‘green’, ‘blue’). Differs from black-gray-white. Quickly now: Name 10 ‘colors’… •Brightness Intensity of the visual experience (e.g., ‘dim’, ‘bright’, ‘light’, ‘dark’) •Saturation Purity of the hue experience (i.e., relative absence of ‘white’ or ‘gray’)(reciprocal of ‘added white’ required for a color-match-to-sample)
- 14. Additive color mixing is creating a new color by a process that adds one set of wavelengths to another set of wavelengths. Additive color mixing is what happens when lights of different wavelengths are mixed. Subtractive color mixing involves the absorption and selective transmission or reflection of light. It occurs when colorants (such as pigments or dyes) are mixed or when several coloured filters are inserted into a single beam of white light. Color mixing