Tuesday, April 14, 2009

Light: In the Beginning...

I would like to spend the next few (if not several) posts discussing light. After all, photography is entirely dependent upon light in one form or another. In the studio we tend to create our own world with light to fulfill our creative vision, or at least try and get close to that vision (we do have a vision don't we?). According to Wikipedia, the word photography "...comes from the Greek φώς (phos) 'light' + γραφίς (graphis) 'stylus', 'paintbrush' or γραφή (graphê) 'representation by means of lines' or 'drawing', together meaning 'drawing with light.'"

Without getting into all the technical aspects, or if you prefer the more colloquial preface, in a nutshell, light is an energy as realized in electromagnetic radiation. In essence, light waves are the same as radio waves, but the wavelength is much shorter because the frequencies are much higher. Visible light has wavelengths ranging from 7x10-5 cm (red) to 4x10-5 cm (violet). This correlates to somewhere in the 1000 million megahertz range, just below Ultraviolet and X-Rays, and that is way up there! These waves travel away from their source at the same speed as radio waves, approximately 186,300 miles per second.

As you might have guessed, not all light is visible. What makes visible light visible is, well, us! by design our eyes can generally see light waves in the range from just above infra-red and all the way up to, but not including ultraviolet. All of these wavelengths and more are contained in sunlight. Fortunately for us, the sun's radiation that hits the earth is concentrated in the visible light wavelengths, which neatly fits our eye's adaptation. Wikipedia has some great articles on light and in particular, sunlight. http://en.wikipedia.org/wiki/Sunlight

The main point is that there are some serious physics involved and for the most part, they are well understood. The last article I read about light had dealt with slowing it down to a literal crawl, nearly stopped. There is also some discussion about light having zero mass at the wave's zero crossing points and possibly entering into another space-time continuum. I'll leave that for the physicists and simply rely on the known principles of light that I can control.

As you can see, I am trying to skirt around the physics of light and thereby not reveal my ignorance of physics. So then you ask, what is the photographer's interest in light? Glad you asked. Primarily we are concerned with three aspects of light, the quantity, the quality, and the temperature. These are common photographer terms for describing light. The more quotidian terms are, Brightness, Contrast, and Color. This is where the next few postings will delve into more detail, so stay tuned.

Continue on to "Quality of Light (Intro)"

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