mirekti Posted March 9, 2021 Share #1 Posted March 9, 2021 (edited) Advertisement (gone after registration) I wonder why not all Leica M lenses have something like 12-15 round blades. Wouldn’t a circle iris be a perfect one? What would be a reason to go with 8, 9 blades that are not round? Edited March 9, 2021 by mirekti Link to post Share on other sites More sharing options...
Advertisement Posted March 9, 2021 Posted March 9, 2021 Hi mirekti, Take a look here Iris blades count and shape - why?. I'm sure you'll find what you were looking for!
jaeger Posted March 9, 2021 Share #2 Posted March 9, 2021 (edited) I have a few vintage lenses from the 50s that have 12+ blades but at the time Nikon started to use 6 blades. Maybe modern lenses are all about cost saving. Edited March 9, 2021 by jaeger Link to post Share on other sites More sharing options...
pgk Posted March 9, 2021 Share #3 Posted March 9, 2021 The 21/3.4 Super-Angulon had a square aperture. I'd guess its mostly a physical thing, on wide angles especially, as fitting in a high number of very small (and consequently thin) blades is obviously going to be more difficult than with a large aperture longer lens. In the past Waterhouse stops allowed for highly circular apertures, but apertures can be any shape and this has consequent effects on the bokeh. Link to post Share on other sites More sharing options...
mike3996 Posted March 9, 2021 Share #4 Posted March 9, 2021 Round blades mean shitty sunstars. I love my 35 Summicron V because how easy it is to get sparkling reflections off of moving water even at f/8. It's an effect I wouldn't personally trade for a bit rounder bokeh balls, blah. Link to post Share on other sites More sharing options...
astrostl Posted March 9, 2021 Share #5 Posted March 9, 2021 5 hours ago, mike3996 said: Round blades mean shitty sunstars. Apparently 7Artisans have figured out a trick: "A special mentioning deserves the aperture diapraghm: this is the best I have seen in any lens yet. It features 12 blades (like we also see in some newer Voigtlander lenses) but they are rounded from f/1.4 to f/2.8 and straight afterwards. This allows for smooth, round highlights slightly stopped down (where the Voigtlander lenses fail) and beautiful sunstars stopped down further (where pretty much all the lenses with 7, 9 or 11 blades, so almost all current Nikon, Sony, Canon and Sigma lenses, fail). I would really love if other manufacturers would adopt this kind of diaphragm design." 1 Link to post Share on other sites More sharing options...
pgk Posted March 9, 2021 Share #6 Posted March 9, 2021 6 hours ago, Al Brown said: Is there an ideal number of blades for a lens to have? Some have 5, some have 20 ..... The 21/3.4 Super-Angulon, effectively has 4 which form a square aperture albeit with curved sides. This works surprisingly well but can give some odd effects in the oof background at times. It probably helps make the lens 'characterful'. Link to post Share on other sites More sharing options...
lct Posted March 9, 2021 Share #7 Posted March 9, 2021 Advertisement (gone after registration) Not sure why a circle should look better than another shape. Those kind of flying saucers look rather boring to me but it's just me. Here's my favorite bokeh balls shape FWIW (Elmar-M 50/2.8). YMMV. Welcome, dear visitor! As registered member you'd see an image here… Simply register for free here – We are always happy to welcome new members! 1 Link to post Share on other sites Simply register for free here – We are always happy to welcome new members! ' data-webShareUrl='https://www.l-camera-forum.com/topic/318720-iris-blades-count-and-shape-why/?do=findComment&comment=4157127'>More sharing options...
giannis Posted March 9, 2021 Share #8 Posted March 9, 2021 16 hours ago, mirekti said: Wouldn’t a circle iris be a perfect one? With regards to bokeh, yes obviously. There are niche reasons to use non-rounded blades. One for instance is exploiting the diffraction patterns and spherical aberrations around the aperture shape, to counteract focus shift. A perfectly circular aperture produces the most focus shift, while straight blades, ninja stars etc. produce less (ninja stars produce the least if I remember correctly). Zeiss did that with the new C Sonnar, alas ruining the perfectly circular bokeh. That said, focus shift is best handled in the optical formula, cause after all the aperture shape only exaggerates or attenuates what's already in the optical formula with regards to focus shift. So overall I think the number and shape of aperture blades in modern lenses is mostly a cost cutting measure, barring a few exceptions. 1 Link to post Share on other sites More sharing options...
mirekti Posted March 9, 2021 Author Share #9 Posted March 9, 2021 (edited) This is a random photo from web. Would the round blades (perfect circle) made these sun lines non existing? In my view it would have made the photo much better than what these 8 blades did. Welcome, dear visitor! As registered member you'd see an image here… Simply register for free here – We are always happy to welcome new members! Edited March 9, 2021 by mirekti Link to post Share on other sites Simply register for free here – We are always happy to welcome new members! ' data-webShareUrl='https://www.l-camera-forum.com/topic/318720-iris-blades-count-and-shape-why/?do=findComment&comment=4157235'>More sharing options...
pgk Posted March 9, 2021 Share #10 Posted March 9, 2021 1 hour ago, lct said: Not sure why a circle should look better than another shape. Depends on what you are trying to achieve I suppose: https://www.lomography.com/magazine/275114-diy-your-own-special-apertures-for-lomography-petzval-lens 3 Link to post Share on other sites More sharing options...
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