articles/Digital/onmattersofresolution-page5

On Matters of Resolution! - part 5 of 1 2 3 4 5

by Mike McNamee Published 01/02/2009

The plain graph shows the distribution of light energy coming from a narrow slit. Most of the light is concentrated in the centre, but there are outlying dark rings and light ones of gradually decreasing strength. When the light comes from a circular aperture, the pattern is revolved into the classic Airy Disc shape as depicted in the grey, 3-D model.

In digitial imaging the limit of resolution is reached when the Airy disc overlaps two or more pixel sites, ie the distance 'C'. When two points are imaged at that size, they 'merge' together and cannot be distinguished as separate points. Typically these could be two stars seen in a telescope.

In the top image two Airy discs are just resolved, only the first black rings of the Airy discs are intersecting. In the lower image the Airy discs are too close and the two points are not resolved.

The diffraction limited aperure of a number of popular Nikon and Canon cameras.

• On Matters of Resolution! page 1
  
• On Matters of Resolution! page 2
  
• On Matters of Resolution! page 3
  
• On Matters of Resolution! page 4
  
• On Matters of Resolution! page 5
  

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