see also:

• photography main index
• the physics behind sunstars and diffraction of light around diaphragm blades
  • When diffraction occurs around an edge like an aperture blade, it creates two visible spikes of light 180° apart and perpendicular to the blade edge
  • On a lens with an even number of blades, the diffraction spikes from opposite sides of the aperture overlap. So n-number of even blades yields n-spikes.
  • With an odd number of blades, there is no overlap. N-number of odd blades yields 2n spikes.
  • Newtonian telescopes give diffraction spikes from stars as a result of the struts holding the secondary mirror in place
  • a circular aperture does not give a sunstar pattern but creates an Airy Disk - a bright circular spot surrounded by concentric circles that represent areas of constructive and destructive interference

• when photographing a scene with a bright light source in the scene such as the sun, or street light, many people like to shoot it with rays of light coming from it
• this is best achieved with:
  • apertures f/11-22 (but remember as you stop down, although you get more defined rays of light, diffraction effects will reduce your image detail and sharpness)
  • use a lens with a 9-bladed diaphragm (odd numbers are best)
  • consider partly obscuring the light source
• see also:
  • http://www.lessgearmorephotos.com/how-to-get-sunbursts-in-photos/