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EXCERPT page containing first few paragraphs. 2022-07-05 03:18:30

With pentagonal diaphragm

Lens Diaphragm Bokeh

With the right amount of defocus and bright points of light, the lens diaphragm can be imaged to show its shape clearly.

These pentagonal highlights do not appeal to me, a lens diaphragm with 9 or more blades generates a much more circular and therefore appealing effect.

Some lenses have as many as 14 blades, which makes for a truly lovely effect on such highlights— think lenses for cinema, and pay attention to the next movie you watch where there are bright out-of-focus spots in the background.

Such highlights can show up at undesirable times and make their presence felt. I consider 9 blades the minimum for good bokeh, though an 8-bladed aperture with rounded blades is good as well.


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Aperture series 2.4,2.8,4,5.6,8,11,16 available in full article
Diaphragm having 11 straight blades
f4 @ 1/12 sec, ISO 200; 2015-03-15 12:00:50
LEICA M (Typ 240) + Summarit-M 1:2.4/75 @ 75mm

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