Leica LTM Summitar aperture blades?

Leica M39 screw mount bodies/lenses
R

rtphotos

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Just curious. When (either year or serial #) did Leica switch from the aperture blades from circular to hexagonal shape on the Summitar lens?

I've heard that the earlier circular style creates better bokeh. If anyone can post them, I'd love to see side-by-side comparisons.

thanks,
rt :)
 
Can't answer the whole question, but can give you a data point. My Summitar, SN 702xxx from 1949 has the round aperture configuration.

Jim N.
 
Here's another data point, my old round-iris Summitar, sn 668338. This website puts the date of manufacture somewhere in 1948.

I sold that one and kept a "hex-iris" model, because I actually liked the OOF-effect it produced. You might see the general effect in the attached photo, which was shot pretty much wide-open.

I seem to recall a discussion (which I now can't find) concerning the difference between these two versions of the Summitar. My understanding is that the earliest Summitars were the ones that had a minimum aperture of f/12.5, not 16; in this way it isn't the iris type that determines the age, but rather the f-stop scale. As for the hex-iris models, I have seen at least a few comments that suggest they were the product of left-over iris assemblies from the Summar production line, and so they show up in only a semi-chronological fashion. Hopefully someone more knowledgeable than myself can shed some light on this.

Either way you slice it, these were great lenses, and remain some of my favorites.

U3326I1159519534.SEQ.0.jpg



Cheers,
--joe.
 
No real answer here either, just a couple of data points. The one Summitar that I have is serial #7250XX with round iris, 2-16 and was made in 1949 according to a web sit. The second one has serial #9389XX with hexagon iris, 2-16 and was made in 1951 according to the same site. I would guess at around 1950 the change was made if these lenses were on either side of the change.

Bob
 
My Summitar is 589XXX, putting it in 1942, round aperture, coated.

I don't think they could re-use the Summar curved blades in a Summar lens, the adjacent lens element is larger in diameter, and less steeply curved.

If they changed to the curved blades late in production, the reason was probably to improve performance at small apertures. Perhaps the change to an f/16 minimum aperture revealed this some issues at small apertures?
 
Thanks all for the info and data points. :)

So far, aside from any possible anomalies that Leica threw into the pot, the switch between round to hex irises appears to have taken place somewhere between 763577 (1950) and 9389XX (1951).

Keep posting your data points!

"planetjoe", good photos are good photos regardless of the len's aperture blade type and bokeh. Thanks for posting your wonderful photograph.

Thank you for keeping this temporarily home-bound photog occupied. ;)

rt
 
John Shriver said:
My Summitar is 589XXX, putting it in 1942, round aperture, coated.

I don't think they could re-use the Summar curved blades in a Summar lens, the adjacent lens element is larger in diameter, and less steeply curved.

If they changed to the curved blades late in production, the reason was probably to improve performance at small apertures. Perhaps the change to an f/16 minimum aperture revealed this some issues at small apertures?
Click to expand...

From November 1945 the coated lenses were produced, so your lens was coated later..

some lenses in wartime had a special coating only for Millitar..

regards,
Jan

(the Summar had the special curved blades for the Agfa Color Filter)
 
It seems that changing from a circular to a hexagonal diaphragm opening is a bit of a step backwards ?

( Or am I missing something ? )

Luddite Frank
 
My 1951 Summitar #931xxx has the hexagonal aperture. I seem to remember reading another thread on the subject that suggested it depended on batches rather than Leitz having definitively switched from round to hexagonal on a particular date. I've no idea why this would be, perhaps someone with more knowledge of Leica history could offer an explanation.

Matthew
 
tripod said:
The question remains: why switch from a nice round aperture opening to a hexagonal?
Click to expand...
Somebody must've had a "who cares!" moment after coming back from vacation?

I don't get why they didn't stick to the circular aperture. My newer Summitar had a hex iris, my older one has a circular one. Both my Summar and Xenar (precursor to the real Summarit) have the "hex" iris.
 
So far we have a latest round iris Summitar No.763577 and I'll add a friend's hexagonal iris that I serviced three years ago, No.813393.
All my Summitars from 487599 to 761603 have round irises and I'm still looking for a hex iris as a user/collector.
487599 has a coated front element and sits on a IIIB.
 
tripod said:
Did you notice a difference, Gabriel?
Click to expand...
Stopped down, yes. The diaphragm dial on the round iris lenses seems to feel smoother than the hexagonal iris, too. They (hex) also seem to close in a non-flat way. Weird.

Ultimately, I think the rounder the iris, the better. But as they acronymize, ymmv ;)
 
According to Puts' book (citing two disagreeing sources), my lens was factory coated. Coating started in October 1941. Not all production was coated, just for "war photographers". Also, it may be a later lens than 1942, Puts' sources note that the serial number block allocated in 1942 for Summitars was still being used in 1945.

As for why the hexagonal iris, the other difference is that the hexagonal iris is not flat. It is curved, domed, and rides very close to the rather deeply curved rear element of the front group. So as the iris opening closes up, it moves toward the front of the lens. This is why I think it was done for optical reasons at small apertures.

It's definitely more expensive to make than the 12 bladed round iris. There are still twelve blades, but in two different shapes. They all have a complex curve. Half of them form the aperture, the others provide stiffness, and cover gaps between the other blades. All the blades are quite narrow.

I only have the hexagonal domed blades in my Summar. I've had them apart, and put them together again. Not something I want to have to do again, a very fiddly project.
 
Hex here, Sr. 7978** LTM. I won't speculate as to why...but this lens has a distinct flavor.

ty_n_amanda_summitar.jpg


fri_after_5_100_dpi.jpg


Todd
 
Here's another data point (took awhile to get around to it): my "keeper" Summitar, f/16 with hex iris, is 903127, which puts its manufacture sometime during 1951. This corroborates, more or less, the data we've been seeing.

Thanks for your comments, rtphotos. I'm glad you've started this thread - the Summitar is really a great little lens. Okay, not so little; after moving on to a collapsible Summicron as my "daily driver", I was personally struck by its heft but rather smallish size. The Summitar, by comparison, seems a larger lens - a real light-collector.

As for the hex iris itself, I'm in conceptual agreement with John Shriver, who pointed out the probable optimization of the Summitar's "new" small aperture. The iris assembly dome moves forward as it closes, reaching a minimum aperture almost directly behind the front element. Forgot I had noticed this.

You guys are going to get me to take the Summitar out again. Good show.


Cheers,
--joe.
 
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