Lenses with circular aperture at all stops

[helohe]

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I was fascinated by the Leitz thalia having a circular aperture at all stops. Does anyone know if there are any other lenses that have always round apertures? (Considering the Thalia are only sold in a set for $245,500)

[a.noctilux]

I have three models Leica and two Jupiter with round aperture:

Summarit 1.5/50mm in LTM mount

Telyt 6.8/400mm and 6.8/560mm

Jupiter 3 and 8  in 50mm

 

almost ...with some

One that can be "almost round aperture" is LTM Collapsible Summicron 5cm.

and Super-Angulon 4/21mm "almost round" is nicer than S-A 3.4/21mm with "square aperture"

[NigelG]

My MS Optical 73 f/1.5 is round at all apertures due to 16 blades.....

[evikne]

One would think that a circular diaphragm was one of the easiest things to achieve when designing a lens. Peter Karbe also says somewhere that this is an important factor for a nice bokeh. So why is this still so rarely seen with Leica lenses?

The current 50mm Summilux ASPH for example has a rather ugly diaphragm shape when stopped down a bit. That's one of the reasons why I use the older pre-ASPH version instead, which is much better in this regard.

Edited August 30, 2019 by evikne

[250swb]

There are also some versions of the f/2 50mm Summitar.

[MarkP]

6 minutes ago, 250swb said:

There are also some versions of the f/2 50mm Summitar.

indeed, I have one with and one without the circular aperture.
Needless to say which one I prefer.

Edited August 31, 2019 by MarkP

[250swb]

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My Summitar is from 1946 and has the circular aperture as well as being coated. I bought it in the days before I realised there were two versions, and I assume the circular blades are the reason for the weird/interesting bokeh wide open, but I wonder if this wasn't seen as a problem at the time, hence the change?

[Guest]

On 8/30/2019 at 11:06 AM, helohe said:

I was fascinated by the Leitz thalia having a circular aperture at all stops. Does anyone know if there are any other lenses that have always round apertures? (Considering the Thalia are only sold in a set for $245,500)

The 90mm f2.4 Thambar. Both 1937 version and 2017 reintroduced version.

 

[colint544]

Yes, when you stop down the 50mm Summilux ASPH a bit, the shape of background highlights is jagged. Is it just for reasons of economy that they put so few aperture blades in the modern lenses?

[RexGig0]

The numerous blades in the Thambar-M make for a quite nicely rounded aperture.

Edited August 31, 2019 by RexGig0

[evikne]

Not only the number, but also the shape of the aperture blades affects the roundness I think.

Edited August 31, 2019 by evikne

[250swb]

6 hours ago, colint544 said:

Yes, when you stop down the 50mm Summilux ASPH a bit, the shape of background highlights is jagged. Is it just for reasons of economy that they put so few aperture blades in the modern lenses?

Well this is what I alluded to above, it's one thing having 'shape' to the background, but when like the Summitar it's swirly, chaotic, and distracting from the foreground who really needs it for the average Leica user? Of course these lenses can be rediscovered later and fawned over like the 50mm Summitar especially when the 'bokeh' revolution hit and the bokeh was more important than the subject itself.

Leaves or flower petals, or fence posts, photographed wide open with a Summitar, give me a break, it's just swirly crap bokeh. It's just using a bad effect because it's fashionable. However, a good photographer will always be able to use the unsettling 'swirl' and bad effect to add to the image, using the lens to add tension and emotion, but first you need the subject. 

[colint544]

A throwaway snap. Leica M Monochrom mk1, plus 50mm Summilux ASPH, stopped down to F4. If you want nice, rounded out of focus highlights, best to stick to F1.4. Does anyone know why Leica reduced the number of aperture blades in this lens? Is it down to cost?

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[pico]

15 minutes ago, 250swb said:

lenses can be rediscovered later and fawned over like the 50mm Summitar especially when the 'bokeh' revolution hit

It should be noted that the 50mm Summitar began with the hexagonal aperture, then post-war switched to a nice, round one, then went back to hexagonal again. I looked for just the right one for years, and when I got it, and used it I wondered why.

Recently I picked up a couple of the close-up attachments for the lens. Why?

Edited August 31, 2019 by pico

[Alberti]

I once read of a lens with even more wierd dia form that it would in for example a face make a smooth transition between in/out focus, sort of give some sonnar look (the latter are my words). But now (since 2005 sort of) we also tend to regard the form of  the background light spots as important. So was it a tradeoff? 

My 90mm M-Elmar has such diaphragma forms too. As does my Canolux 50  - the canon 1.4 LTM has an even more severe form of the dia as above; I initially thought of selling it again (but was withheld - should I then also sell my M-Elmar and get my great Elmarit back?    No . . .)

[a.noctilux]

Elmar 9cm ...other older Elmar also,

forgot that this old LTM Elmar 9cm f/4 has round aperture

also old Elmar 50mm f/3.5 and f/2.8 = round aperture opening at all stops

 

9cm f/4 Elmar was created for light/less expensive offering in place of Elmarit/Summicron(later)/Summarex

only one that has round aperture at all settings, in those 90mm that I own.

 

But later on Elmar-M has no more this feature (50mm has "hexagonal" opening, Macro-Elmar-M 4/90mm not so round aperture when close down, etc.)

 

[mmradman]

So called Ninja star or serrated OOF highlights are evident with Summilux M 50mm ASPH but also with well regarded Summilux M 75mm.  Other well regarded lens are not immune, fortunately to a lesser degree, APO Summicrons M 50 and 90mm. And than there are also onion rings, result of pressing glass blocks to produce ASPH elements, very widespread with modern M lenses.

 First time I encountered serrated aperture or rather became aware of was with APO Elmarit R 180mm, initially I thought something was wrong with the lens but later found it with some old Pentax SMC M lenses.

Bokeh emphasis is product of digital era but why some lenses have serrated and some smooth aperture when stopped down is bit of a mystery, perhaps economising on number of blades and suggesting to use them wide open.  

Final thought, maybe Leica’s subtle way of saying don’t shoot against strong backlight or be bokeh fanatic - the trend will pass 😅

[evikne]

I have long wondered: Does the shape of the diaphragm only affect small OOF light sources (AKA "bokeh balls")? Or it is possible that it can also affect all other unfocused areas in the picture, only less prominent?

[jdlaing]

27 minutes ago, evikne said:

I have long wondered: Does the shape of the diaphragm only affect small OOF light sources (AKA "bokeh balls")? Or it is possible that it can also affect all other unfocused areas in the picture, only less prominent?

I personally think it does.

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Hallo,

Look here: Leica M

[adan]

On the question of WHY many M lenses have star shapes and not circles, at this or that setting:

- Question of overall lens size - the aperture blades do have to tuck away into the lens barrel unseen at full aperture, and that enforces a certain size and shape. And size is always a prime consideration in putting together an M lens. What can fit in a fat-waisted Thalia is not what can fit in a regular M lens.

- Evenly-spaced f/stops - look at the pre-1960 lenses that may have round apertures, and they also often have non-linear spacing of the f/stop markings. E.G. 50 f/1.5 Summarit - the physical spacing of the aperture marks is  f/1.5......f/2....f/2.8...f/4...f/5.6..f/8..f/11.f/16. Similar for the Thambar, Summar and f/3.5 Elmar 50.

That went distinctly out of favor with practical photographers, who wanted the same movement and spacing to get from f/1.4 to f/4 as from f/5.6 to f/16 (I know I do). Which - since the primary function of the aperture is to pass exponentially-spaced amounts of light - meant the blades had to have weird shapes (S-curved edges or rounded tips) to cut into the aperture and tweak it to a precise area.

- Lenses that have a large aperture range - e.g. f/1.4 to f/16 - have even more trouble getting blades that are large enough to cover most of the f/1.4 glass at f/16 (7 steps) and still "disappear" at f/1.4, compared to a smaller f/3.5 lens to f/22 (5.5 steps). The 50 Summar has weird, criss-crossing extra blades ("parquet-floor" pattern) so that each blade can be narrow enough to tuck away at f/2, yet expand side-by-side to block most of the glass at f/12.5 (and Leitz still couldn't get all the way to f/16, let along f/22, with that f/2 lens).

Most medium-format lenses have 5 blade apertures - and they show in pictures. The 21mm f/4 Super-Angulon-R also had 4 blades (and "square" bokeh ). Not sure why, except that stopped-down "background blur" may be a low priority in designing a 21mm f/4.0 lens. There isn't much of it

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Edited September 2, 2019 by adan