In many big-budget movies one see octagonal bokeh balls, in TV talk shows even pentagonal ones are common! Because these movie budgets are not small and the cameras in general are very expensive to rent, I don't think the number of aperture blades in the lenses chosen is due to a budget constraint. Are there any reasons in general why there are these big-bucks lenses with such a visible visual "flaw"?

In stills photography lenses I recall at least a certain Leica Summilux 35mm model which also chose to use octagonal arrangement, which occasionally can result in an "ugly" bokeh, all subjective of course.

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    \$\begingroup\$ Come to think of it, Angenieux don't even mention their blade design. Interesting question! \$\endgroup\$
    – flolilo
    Nov 27, 2017 at 10:41
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    \$\begingroup\$ Probably better to ask over at the Video Production Stack Exchange: video.stackexchange.com \$\endgroup\$
    – Mike Dixon
    Nov 27, 2017 at 11:25
  • \$\begingroup\$ @MikeDixon: thanks for suggestion. I'll try my luck there if no satisfying answer comes up here \$\endgroup\$
    – mike3996
    Nov 27, 2017 at 11:57
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    \$\begingroup\$ Many times when you see lens flare in movies, it is added. When the director of photography wants lens flare to add to the scene, it gets added in the desired spot, not usually left to the lens. I worked in special effects for film for 9 years and flare is a very common effect. \$\endgroup\$
    – Itai
    Nov 27, 2017 at 17:07

1 Answer 1


Jumping diaphragm used in AF-lenses is very critical part of lense. To make it manufacturer needs high precision and has some problems in avoiding of friction. A smaller number of blades allows to lower requirements.

  • \$\begingroup\$ I believe all professional cine lenses (and most Leica lenses) are manual focus only. \$\endgroup\$
    – mike3996
    Nov 27, 2017 at 11:52
  • \$\begingroup\$ Maybe. But some expensive manual Hasseblad lenses has only five. Where is the truth ^) \$\endgroup\$ Nov 27, 2017 at 12:04
  • \$\begingroup\$ Yeah I mean clearly there has to be a reason to reduce the number of blades because these are manufactured to people and companies for whom money is no object \$\endgroup\$
    – mike3996
    Nov 27, 2017 at 12:07

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