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A little question about Sigma 14-24 sunstar

Started Jun 4, 2020 | Questions thread
WindwardHaole Senior Member • Posts: 1,550
Odd and even

This from add copy:

The Canon 16-35 f/2.8L II has 7 aperture blades which will create 14-point stars from specular highlights when very narrow apertures are used, the Canon 16-35 L IS f/4 has 9 rounded aperture blades which will create 18-point stars

This from Wikipedia:

Diffraction spikes due to non-circular apertures

Iris diaphragms with moving blades are used in most modern camera lenses to restrict the light received by the film or sensor. While manufacturers attempt to make the aperture circular for a pleasing bokeh, when stopped down to high f-numbers (small apertures), its shape tends towards a polygon with the same number of sides as blades. Diffraction spreads out light waves passing through the aperture perpendicular to the roughly-straight edge, each edge yielding two spikes 180° apart.[6] As the blades are uniformly distributed around the circle, on a diaphragm with an even number of blades, the diffraction spikes from blades on opposite sides overlap. Consequently, a diaphragm with n blades yields n spikes if n is even, and 2n spikes if n is odd.

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