Rayleigh’s Curse 2016

airy_disk_spacing_near_rayleigh_criterionJust in time for Halloween!  

Ok, so it’s not really a curse, although until now, for anyone involved in optics, including photographers, it sort of has been.  Here’s why:

Optical resolution is the ability of any optical device (telescope, microscope, binoculars, cameras) to distinguish fine detail.  It is limited by something called Rayleigh’s Criterion, named after Lord Rayleigh, a nineteenth century physicist.  What this criterion says, very simply put, is that for small bits of detail to be visually clear, the centres of their diffraction patterns must be farther apart than their widths.  In the example here, the top image represents their being farther apart than their widths, the middle image shows them meeting at that width and the bottom image shows them closer than their widths.

Schmeh” you say?  “I’m not into science stuff.”  But if you are a photographer,  you actually are into science – very much so.  From its very beginnings, in the days of Niepce and Daguerre, photography has been the product of science and it continues to be.

So back to Rayleigh’s criterion… It is the “curse” that causes diffraction, the hard limit on our ability to see finer details in our images.  It’s that bit of blurriness that we try so hard to avoid, in order to get the sharpest images possible, the limit of physics holding us back.  But recently, scientists at the Complutense University of Madrid have managed to break this limit, opening up the possibility for greater resolution in the world of optics – in our world of photography.

Presently we are using information taken from the intensity of light, but the international team in Madrid has discovered that more information can be extracted from the phase of light.  In doing so, they managed to reach resolutions seventeen times beyond the Rayleigh limit.  So the “limit” has not necessarily been in the nature of optics, but rather in our own methods!  A shift in method could offer exceptional new possibilities to everyone using optics, including photographers.

See, you are into science.  😉


Image By Spencer Bliven (Own work) [Public domain], via Wikimedia Commons

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