Monday, November 16, 2009

Photography with Imre Z. Balint: Episode 1 – Aperture

Yeay! I finally finished my first webisode of a series I’ve always wanted to do about various topics in photography. The first subject I discuss is aperture, a very important aspect of taking great pictures. In my video I show what an iris diaphragm looks like, which is the mechanical part in a lens that controls the aperture that either restricts or permits additional light to penetrate the lens (thus light that hits the film or sensor).

In a (tiny) nutshell, here’s a summary of aperture:
  • The aperture of a lens controls the amount of light that can pass through it to the film or sensor
  • Larger aperture = more light passing through, smaller aperture = less light passing through
  • This sounds odd, but: larger aperture = smaller f-number, smaller aperture = larger f-numbers (inverse relationship)
  • Depth-of-field (DOF) is how much of an image is in focus
  • Large apertures (smaller f-numbers) means smaller DOF; small apertures (larger f-numbers) means larger DOF
  • Different lenses behave in different ways; wide angle lenses generally have large DOF even when small f-stops (aperture wider open) are used.
What can different aperture (or f-stop settings) be used for?
  • When shooting portraits, it’s often more pleasant to blur the background with only the subject in focus, thus smaller f-numbers (wide open apertures) are used.
  • When shooting subjects a short distance away (e.g. within 5 meters) with a telephoto (aka zoom) lens, DOF is usually quite small, however, at the same aperture setting when shooting a subject at a large distance (e.g. 20 meters or more), the DOF becomes larger. So DOF also depends on distance, not just the aperture setting.
  • Most lenses have f-stop “sweet spots” where a particular or certain range of aperture results in a sharper photograph.
Some resources on aperture:
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