Canon LTM Straight aperture blades on canon RF lenses?

Canon M39 M39 screw mount bodies/lenses
redimp

redimp

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Hello, I am looking to get three matching lenses from canon for a very specific application. According to my research 35/1.8, 50/1.8 and 85/1.8 should match well in terms of coatings/aberrations.

my application however requires as round of a bokeh shape as possible and I’ve noticed that 35 and 50 at some stops have the ninja star bokeh.

Are there variations of these focal lengths that have round aperture shape at all stops? I saw a 50mm serenars that have perfectly round blades, and on gele end I saw matching serenars with nlue coating too, but nothing for 35.

would appreciate any suggestions !
 
I doubt that ther is anyone alive who has studied the esoterica of Canon rangefinder lenses more deeply than Peter Kitchingman. He wrote and sells the most detailed book on the subject, ‘Canon M39 Rangefinder Lenses 1939-1971 - A Collector’s Guide’. He was recently interviewed on the Camerosity podcast https://www.mikeeckman.com/2022/01/e...r-kitchingman/ and I believe they have current contact information for him on that page. It may be worth your while to seek him out.
 
 
davhill said:
In today's Canon world, “RF” means a modern full frame mirrorless system/lens. For LTM Rangefinder lenses look under “S lenses”.
Click to expand...

Yes, you're correct davhill! I did mean to link to the S lenses, but somehow borked the URL. I've edited my post so that it hopefully directs to the Canon rangefinder lenses.
 
Actually a difficult question without lenses in hand. Number of blades doesn't answer the question. The answer about curved blades I think meant circular-ish aperture at all stops (and in between :) But, just knowing the blades are curved doesn't answer the question. Only knowledge of aperture shape across it's range can answer the question. I will have to check my Canon RF lenses and watch aperture shape over the range and report back. I have several.
 
As rfaspen notes, "curved" doesn't really answer the question. The eight blades of the 50/1.8 are curved, but they have a heel which intrudes into the circle to create a jaggy shape in the wider apertures. It's irregular at /2 and /2.8, becoming a more regular star shape at /4 and /5.6 (this being what the OP is wishing to avoid.) The heel is hidden by /8 so the shape becomes a regular octagon at /8 and smaller, and by /22 its as near to round as my eye can make out. Fascinating, really, how that mechanism works :)
 
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I couldn't find any 35 Canon lenses in the cupboard so can't help there. I found other focal lengths, but no 35s.. Hmmm.
The advice above to watch YouTube reviews seems good. Those people often show the aperture opening and closing over it's range.
 
I have an old Canon rangefinder lens repair manual and all of the aperture blades shown have a basic "hockey stick" shape. Some of the edges are curved, others are primarily straight. So it depends on the lens.

Jim B.
 
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