Diffraction, Airy Disks and implications


Jul 10, 2015
Alan shows in his excellent diagrams that a 2x TC cannot improve the resolution of a lens.
But this does not mean it will not increase the resolution in an image. If two points are diffracted, but scattered over more pixels, then the
chances of seeing a dark pixel between the two lighter points is increased.

I've just run a calculation with a nominal 400mm f/5.6 lens and two overlapping Airy disks. The results show that spreading the light over more pixels does improve the resolution, taking the Airy disk radius as 4 microns and a pixel size of 4 microns too which is about that of a 7D2 or 5DS. I hope to show these results once I've persuaded Excel to display them easily.