Little Egret and Caustic Network

September 13, 2023

DSC_6431 Garzetta con il riflesso delle venature d'acqua nella parte interna dell'ala

Photographer: Emanuele Nifosì  

Summary Author: Emanuele Nifosì; Jim Foster

In this photo, which shows a little egret in flight over the Pantano Longarini (Italy), we can see the phenomenon known as a caustic network (barbàglio in Italian) on the egret’s seaward wing. When water is relatively clear and the Sun is shining, undulating water surfaces can act like an arrangement of concave and convex lenses. These "lenses" result in an uneven brightness distribution at the bottom of a shallow body of water (often seen in swimming pools) or on objects just above the sea-surface. It's the height of the waves that determines the focal length of the formed "lenses." Caustic networks are most easily observed when the water's depth is about five times the wave's crest-to-crest distance.

Photo taken on June 2, 2023, at 09:12 local time.

Photo details: Nikon D700 camera; Nikkor 200-500 mm; TC-14E ​​III; ISO 1,600; f/16; exp. 1/1600 second exposure.


Pantano Longarini, Ragusa, Sicily Italy Coordinates: 36.707975, 15.001181

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Egret and Fish with Caustic Network