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EXCERPT page containing first few paragraphs. 2023-03-29 17:50:32

Concentric Diaphragm Echo Bokeh (from diffraction)

Diffraction around the lens diaphragm can generate concentric rings, a lens “diaphragm echo”.. These concentric rings have the number of side of the lens diaphragm, which distinguishes this type of bokeh from aspheric ring bokeh.

As per Dr. Nasse of Zeiss:

This pattern simply reminds us that we simplify a bit when we talk about light rays – many things in optics can only be understood on the background of the wave nature of the light. You see here a nice example of diffraction pattern, diffraction at the edges of the iris blades. Theory has been established by Jean Augustin Fresnel in 1818.

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Diffraction bokeh on the lens aperture (actual pixels)
f5.6 @ 15.0 sec, ISO 50; 2016-01-22 20:56:36
Sony A7R II + Zeiss Milvus 85mm f/1.4

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