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Broad introduction to the field of photography, covering topics including human color perception, color theory, lighting, composition, how cameras work, optics, etc.Released under Creative Commons Attribution- Share Alike 3.0 United States License, this is an original work with illustrations sourced from the Wikimedia Foundation, and the author's own photographs.

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  • Photography WorkshopKen Stewart, creativexposure LLC

  • This work is licensed under the Creative Commons Attribution-Share Alike 3.0 United States License. To view a copy of this license, visit http://creativecommons.org/licenses/by-sa/3.0/us/ or send a letter to Creative Commons, 171 Second Street, Suite 300, San Francisco, California, 94105, USA.

    Many of the images and diagrams used in this work are taken from the Wikimedia Commons (http://commons.wikimedia.org/wiki/Main_Page), and are reproduced under the terms of the GNU Free Documentation License, Version 1.2. Others as noted are used with the permission of their authors under the terms of the GNU Free Documentation License, Version 1.2.

    All remaining images are the authors own work and are licensed under the Creative Commons Attribution-Share Alike 3.0 United States License.

  • Modules Art & The Nature of Light Anatomy of The Camera Aperture, Time & Sensitivity Automation - Help or Hindrance? Focus on Lenses Lighting Putting It All Together Production - Before And After The Click

  • Art & The Nature of Light

  • photography (f-t!g'r-f")from Greek photos (!!"!#), light, and graphos ($%&!#), writing - n.

    1. The art or process of producing images of objects on photosensitive surfaces.

    2. The art, practice, or occupation of taking and printing photographs.

    3. A body of photographs.

  • Light

    Light is essential to vision, photography and all the visual arts

  • The Photographers View Light is what makes images possible Lights artistic properties include its color value (or hue),

    color purity (grayness or saturation), intensity (brightness), direction, spread (narrow beam, omnidirectional etc) diffuseness (hard or soft), duration (continuous, or in bursts), size/distance of the source relative to the subject

    Many of these properties are combined when we talk about different kinds of light in everyday usage - bright sunlight, cloudy daylight, open shade, fluorescent light, incandescent light

    For example, midday sunlight is white in color, very bright, comes from almost overhead, hard yet omnidirectional, continuous, etc

  • Hard or Soft Light?

    What kind of light are we seeing here?

    Hard or soft?

    Bright or dim?

    Directional?

    What color of light?

  • Hard or Soft Light?

    What kind of light are we seeing here?

    Hard or soft?

    Bright or dim?

    Directional?

    What color of light?

  • High or Low Key?

  • High or Low Key?

  • A Physicists View of Light Light is a form of electromagnetic radiation, comprised of photons,

    which have both wavelike and particle-like properties The four basic properties of light are reflection, refraction, diffraction,

    and interference Light rays travel in straight lines, but they be transmitted through

    different substances (or mediums), they can be bent (or refracted) when they travel from one medium to another, they can be reflected, absorbed or when they strike a surface, and they can be scattered (or diffracted) by obstacles and certain surfaces.

    When light of different colors (wavelengths) is refracted by different amounts (or dispersed) within a material, that material can be used to make a prism that splits white light into its components

    When light of one color hits some materials, it can cause the material to emit light of a different color - this is called fluorescence.

  • More On The Physics of Light In the vacuum of space, light travels at a maximum velocity (c) of

    299,792,458 meters per second, or about 186,000 miles per second. When light travels in anything other than a vacuum, like in air or glass, its speed will always be lower than the maximum

    Lights speed can increase (but never above c) or decrease when it travels from one medium to another. This change of the lights phase velocity is what causes refraction

    The primary physical properties of light are wavelength or frequency, intensity and polarization

    We perceive light of different wavelengths as having different colors, and its intensity as brightness. Many humans can learn to directly perceive polarization of light, and many animals can. Humans can see light with wavelengths in the range 400-700nm; birds and insects can often see light with shorter wavelengths into the ultra-violet, and some animals, eg pit vipers, can sense light with longer wavelengths, into the infra-red

  • The Electromagnetic Spectrum

  • White Light White is the color humans perceive when all

    three types of cone cells in the eye are stimulated in almost equal amounts, and with high brightness

    White light can be generated in many ways. The Sun, fire, and electric incandescence are thermal light sources. Other light sources such as fluorescent lamps and light-emitting diodes produce light by spontaneous emission

  • White Light & Color Temperature Thermal light sources give off a broad spectrum of frequencies

    (white light) characteristic of black-body radiation; Light from the Sun comes from its 6000K/10000F surface, the

    chromosphere, Incandescent light comes from the 2500K tungsten filament in

    a light bulb. Compared to one another, midday sunlight is more bluish,

    and incandescent light and sunlight around sunrise and sunset (during the so-called golden hours) are more yellowish.

    Fluorescent lights, LEDs and the xenon tubes in flashes produce light by spontaneous emission; fluorescent light is somewhat greenish and white LEDs often give bluish light; the light from a xenon flash is a close match for sunlight.

  • Black-Body Radiation

    This diagram provides a convenient excuse for the gratuitous use of the term black-body radiation and the ultraviolet catastrophe, which not only sounds really frickin cool, but would also make a totally rad name for a band

  • Tungsten vs. Daylight Tungsten, at around 2,500K, is about the lowest

    color temperature we encounter on a daily basis Sunlight, at around 6,000K, is one of the highest

    color temperatures we encounter

    White balance set for 2500K White balance set for 6000K

  • White Light & Color Temperature Thermal light sources give off a broad spectrum of frequencies

    (white light) characteristic of black-body radiation; Light from the Sun comes from its 6000K/10000F surface, the

    chromosphere, Incandescent light comes from the 2500K tungsten filament in

    a light bulb. Compared to one another, midday sunlight is more bluish,

    and incandescent light and sunlight around sunrise and sunset (during the so-called golden hours) are more yellowish.

    Fluorescent lights, LEDs and the xenon tubes in flashes produce light by spontaneous emission; fluorescent light is somewhat greenish and white LEDs often give bluish light; the light from a xenon flash is a close match for sunlight.

  • Correlated Color Temperature The black-body radiation spectrum

    describes the distribution of wavelengths in the ideal theoretical case

    In practice, real light sources have anomalous peaks and valleys in their light spectrum due to chemical impurities, filtration effects, etc

    Perceptually, there is an arbitrary number of spectra that more-or-less approximate a given ideal black-body spectrum

    A spectrum that does not conform to the ideal is assigned a so-called correlated color temperature The CIE 1931 x,y chromaticity space, also showing the

    chromaticities of black-body light sources of various temperatures (Planckian locus), and lines of constant

    correlated color temperature

  • When Blue is Hot and Red is Cold ...

    Be careful not to confuse color temperature with the psychological associations of blue with cold, and red with hot

    Bluish color temperatures are actually much higher than reddish ones - the opposite of our everyday associations

    If youve ever heated something until it gets white hot, you will have seen it go through red to orange to yellow before it reaches white heat - so red is the lowest color temperature you observed

    Photographic filter names perpetuate this confusion - a blue filter (like a Wratten 80 or 82) is called a cooling filter and an orange filter (like a Wratten 81 or 85) is called a warming filter even though the color temperature of the light that passes through them is shifted in the opposite physical sense

  • Tungsten vs. Daylight Tungsten, at around 2,500K, is about the lowest

    color temperature we encounter on a daily basis Sunlight, at around 6,000K, is one of the highest

    color temperatures we encounter

    White balance set for 2500K White balance set for 6000K

  • Flash - Lightning in a Bottle Photographic flash tubes, aka strobes, flash guns or

    speedlights(*) produce very intense light for a very short period (~1ms or less) by creating a high-voltage electrical discharge through a clear glass tube filled with xenon (or sometimes krypton) gas

    The first photographic flashes were created with magnesium powder, then later, strips of magnesium metal in a glass bulb, and then finally zirconium metal, which gave an even brighter light

    Light from a flash tube has a complex spectrum and a color temperature around 5600K, but for most purposes is a close analog for natural sunlight

    * Irritatingly, Nikon and Canon trademarked similar words for their battery-powered flashes. Nikon calls theirs the Speedlight, Canon, the Speedlite. Because of this, many photographers use the term in a generic sense for battery-powered portable flashes.

  • Colored Light Color is a