Monday, May 9, 2011

Class #3

Today we learned about lenses and how to operate our camera in Manual mode (adjusting f-stop, ISO and shutter speed).  We scratched the surface with more to come.

Focal Length and Angle of View
- Your lens is the single most important tool of as photographer.  The camera is just a dark box, while the lens manipulates the light and projects the image to the chip.
- When adjusting your focal length - you are expanding and contrasting the field of view and manipulating the spacial relationship.
- Lenses are measured by their focal length.  This is the theoretical measurement from the center of the lens (nodal Point) to chip when focused at infinity.  The smaller the focal length,  the wider the angle of view.  Longer lenses have smaller angles of view, resulting in a greater image magnification.
   * 20mm lens is a wide-angle lens with an angle of view about 90 degrees
   * 50mm lens is considered a normal lens because the angle of view is roughly that of our vision - 45 degrees
   * 300mm lens has an 8 degree angle of view

- Wide Angle - Show more of a scene than a normal lens.  They exaggerate and expand perspective by making foreground objects large and distant objects small.  Wide lenses can distort lines close to the edges further adding to the illusion of perspective.

- Normal Lens - You are pretty much showing the viewer what they would see through their eyes.  A Normal focal length is around 35mm.

- Long lenses (telephoto) - Pull subjects closer to the camera.  Long lenses tend to compress the scene making objects appear closer to one another than they are.  They have have less ability to maintain focus in front of and behind the main subject.  This sharpness fall-off can help to restore the illusion of depth.

Manual Exposure Fundamentals
To find the correct exposure for your picture, you need to find a balance in the amount of light in your scene to the amount of light your chips needs to capture the tones and colors accurately.

- f-Stop or Aperture - This is the diaphragm of your lens just before you release the shutter button.  The "f" in f-stop stands for factor, as the number is the result of dividing the focal length of the lens by the actual size of the opening.  All you really need to know is - the bigger the number, the smaller the hole.

- Shutter Speed - This is the amount of time the shutter stays open.  It is expressed as fractions of a second.  So 125 is 1/125th of a second.  The important thing is - a slower shutter speed can cause blur.

 - ISO - This is the numerical expression of your chip's light requirement....or adjusts the sensitivity of your chip.  This is the amount of light that the chip needs to accurately represent tones and colors.  The higher the ISO - the more electricity and more robust charge.  This can also create noise in your picture (more next week).  For low light scenes you'll want a higher ISO, starting around 1600.  For sunny days, start with an ISO around 200.

- Meter - To make sure you're reaching the correct balance of light - you need to read your light meter.  The light meter reads the amount of light in your scene and guides your selection of the shutter speed and f-stop selection - after you've set your ISO.

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