Why are Leica using less aperture blades on newer designs?

[tedd]

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An easy example is the 50mm Summilux. A common complaint with the ASPH version is the 9 aperture blades create a ninja star highlight shape between f2 and f8. The old version, with 12 blades, does not do this. I'm sure there is a very good reason for dropping the extra blades, and obviously bokeh balls are far from everything, but I am interested to know "why." 

I do realise also that 9 blades should be more that enough to create round highlights (the Olympus 45mm f1.8 is a great example of a cheap, 7 bladed lens with lovely OOF), so again, what was Leica prioritising here? 

 

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[frame-it]

18 minutes ago, tedd said:

what was Leica prioritising here? 

 

Just a Guess :

 

maybe costs? more blades = thinner blades, more delicate alignment, more chances of damage, special grease, more costly repairs etc

[Anbaric]

70 years after the Summitar, we still don't know why Leica switched between 10 and 6 blades in the same lens.

[Jeff S]

Jeff

[jaeger]

For better sun star maybe?

 

[Capuccino-Muffin]

Fast refresh course on basics lens’ construction:

-Odd number of aperture blades creates starburst effect with twice as mant rays.

-Even number aperture blades create round bokeh balls.

 

 

 

[Gobert]

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Agree, although this does not give an appropriate answer to the question of TS why Leica applies less aperture blades in its recent lens designs?

[pippy]

As Anbaric has already intimated in post #3 this is hardly a recent phenomenon with Leitz optics; there are many examples spread throughout the vast majority of their history.

In addition to the '10 blades down to 6' of the Summitar I would like to nominate the change between the 1958 (v1) and 1963 (v2) 21mm Super Angulon lenses as being a 'Stand-Out' example. The original f4 version had 9 blades but when the lens was given a redesign for the f3.4 release the diaphragm - very unusually - now had only 4(!) blades. I can't think of any other high-quality lens with such a low blade-count.

As far as the more recent offerings are concerned; perhaps someone here with Peter Karbe's 'ear' might ask, very politely, for a response?

Philip.

Edited June 19, 2022 by pippy

[lct]

1 hour ago, Gobert said:

Agree, although this does not give an appropriate answer to the question of TS why Leica applies less aperture blades in its recent lens designs?

Because it is not true?
28/2 asph v2: 10 blades
35/2 asph v2: 11 blades
35/2 apo: 11 blades
50/1.2 asph: 16 blades
50/2 apo: 11 blades
75/1.25 apo: 11 blades
90/1.5 apo: 11 blades

[stephan54]

Sustainability.

[farnz]

It's because the output of the aperture blade mine in Portugal has drastically reduced.  They had located a very rich seam of aperture blades in the mine decades ago but this is nearly exhausted now and they've only managed to locate small seams in the meantime so the extraction price is rising owing to the same overhead costs for reduced yield.  It was thought that they'd managed to locate a new, rich seem recently but unfortunately it was only diamonds.

Technological advances in location and extraction equipment bring hope but so far it is only locating and extracting apertures but not the blades.

Pete.

Edited June 19, 2022 by farnz

[a.noctilux]

One of good news is latest non apo 50mm Summicron-M always offered with 8 blades, but cheaper/smaller Summarit-M 50 has nine "rounder" blades.

Changed for a bit more (+1) as Summicron-M 35mm asph. first with 8 blades, then second version with 9 same number as Summarit-M 35mm.

When I need round aperture no 50mm can beat Summarit 1.5/50 (I don't know how many blades, just a lot to be round from wide open)

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[Anbaric]

Experiments with 20 iris blades ended poorly.

[Stuart Richardson]

It will be interesting to know what the actual reasons are. That was one thing that always baffled me with the Hasselblad V lenses with their pentagonal irises, while their FE lenses had beautiful round apertures. If you wanted smooth bokeh it helped to stick to wide open. Thankfully, the 80mm 2.8 planar is actually quite good wide open. The only clue I have was that the 110mm FE lens tends to have sticky aperture blades, but I was told it was because the lens barrel was a very tight fit (the glass is so large and takes up almost the whole body of the lens). I figured the fewer blades were more reliable as there were fewer things to gum up as the lenses stop down, but since the M lenses do not have irises that have to move quickly, it is a bit odd that they do not more blades with circular apertures.

[Jeff S]

4 hours ago, lct said:

Because it is not true?
28/2 asph v2: 10 blades
35/2 asph v2: 11 blades
35/2 apo: 11 blades
50/1.2 asph: 16 blades
50/2 apo: 11 blades
75/1.25 apo: 11 blades
90/1.5 apo: 11 blades

Yes, and the 35 Summicron ASPH v.2 (introduced 2016) has 3 more blades than v.1.

Jeff

[lct]

Would be interesting to recall when Leica began to refer to the number of blades in its technical data. 2016 as well? Press information from Jan 14, 2016 attached below.

 Press information_New generation M Lenses.pdf

[Jeff S]

Recollection of that communication is the basis for my understanding; otherwise I pay little attention to technical details, more interested in actual results and handling. The first version suits my needs well enough.

Jeff

[lct]

One could ask why are Leica using more instead of less aperture blades on newer designs then. The answer being that young people prefer round bokeh balls i suspect. But they don't want onion rings apparently. Now if they don't want onion rings why asking for onions in the first place? . Be that onions, tomatoes or whatever those round things are too boring for me. My favorites are the 6 blades of the Elmar-M 50/2.8 so far but i don't hate the 4 ones of the S-A 21/3.4 either.

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[LocalHero1953]

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The Thambar-M retained the 20 blades of the original. As a result the bokeh balls are truly spectacular and have 3d pop. 

Edited June 20, 2022 by LocalHero1953

[adan]

44 minutes ago, lct said:

My favorites are the 6 blades of the Elmar-M 50/2.8 so far but i don't hate the 4 ones of the S-A 21/3.4 either.

Thanks for that. A couple of other thoughts spring to mind.

1) If Peter Karbe says we don't have to stop down Leica lenses - why worry about the number of blades we'll never see or use.

2) The most successful and professional of the medium-format film systems - Hasselblad - standardized on five blades in most (if not all) of their lenses. For 60 years. Doesn't seem to have stopped thousands of pros earning millions (if not billions) of dollars with that gear. Often with some of the dreamiest bokeh in the business.

https://www.pebbleplace.com/reviews/medium_format/hasselblad_110mm_planar/index.html

...........

As to the original question, I guess one would have had to be a fly on the wall of Leica lens-engineering meetings 1960-present to know for sure, But I would imagine cost was one reason, and robustness may have been another, along with the ever-present problem for Leica M that the blades have to function in as compact a lens as possible.

One blade doing the job of two is less expensive (and yes, even Leica does have to consider costs), and one wide blade may be less prone to twisting/torquing around its length than two narrower blades.

Another factor may be that Leica has used L-shaped aperture blades for a long time - the blade pivots from the end of one of the legs of the L, and the other leg is what actually cuts off light when stopping down. Which may be because of.....

Also remember that many pre-1960 many-blade lenses had non-linear aperture mechanisms - the aperture ring had to be moved a lot more to stop down one stop from f/2 to f/2.8 than from f/11 to f/16. It was an innovation across all lens makers to make the aperture setting steps evenly spaced, by changing the geometry of the blades and their movement. Because some photographers asked for that, and it would eventually become required for coupled metering systems (at least in SLRs).

For example, the 50mm Summarit f/1.5 had 16 blades, and uneven stop spacing. By 1980 (at least) the successor 50mm Summilux f/1.4 had even spacing, but only 12 blades.

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