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Double diaphgram
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PostPosted: Wed Jun 06, 2018 6:57 pm    Post subject: Double diaphgram Reply with quote
any experiences about old double diaphragm lenses?
I have come across a soviet one from the 70's. May buy it.
Here i found only one thread about this kind of lenses (maybe other threads searchable with less obvious keywords....) : http://forum.mflenses.com/double-diaphragm-lenses-t14717,highlight,%2Bdouble+%2Bdiaphragm.html


PostPosted: Thu Jun 07, 2018 2:10 pm    Post subject: Reply with quote
The Sony lens simply has a double aperture for producing the smoothest OOF area with rounded blades. It is also stepless.


PostPosted: Thu Jun 07, 2018 3:16 pm    Post subject: Re: Double diaphgram Reply with quote
landstrykere wrote:
any experiences about old double diaphragm lenses?
I have come across a soviet one from the 70's. May buy it.
Here i found only one thread about this kind of lenses (maybe other threads searchable with less obvious keywords....) : http://forum.mflenses.com/double-diaphragm-lenses-t14717,highlight,%2Bdouble+%2Bdiaphragm.html


A russian lens with double aperture? Which type is this??


PostPosted: Thu Jun 07, 2018 7:09 pm    Post subject: Re: Double diaphgram Reply with quote
kds315* wrote:
landstrykere wrote:
any experiences about old double diaphragm lenses?
I have come across a soviet one from the 70's. May buy it.
Here i found only one thread about this kind of lenses (maybe other threads searchable with less obvious keywords....) : http://forum.mflenses.com/double-diaphragm-lenses-t14717,highlight,%2Bdouble+%2Bdiaphragm.html


A russian lens with double aperture? Which type is this??


well, I was just about to explain better, as i am not sure it's double diaphragm; rather a double iris set by one aperture ring. But... the lens I have in mind had many variations in its timeline. I have one in fact, for my Kiev-6s bodies, so Pentacon Six mount. The one I am considering is the same but for my Salyut, so bayonet-V mount. I try to keep lenses (and expenses) tidy, so I better buy the bayonet-V, and use them on the Kiev-6s with adapter rings, but it's not easy, depending when and how I find lenses. And of course it's valid for the soviet lenses, the only ones I know of with bayonet-V (Hasselblad 1000F ones ???) , as for the Kiev-6s/60, there are Jena and other german lenses.

anyway, that's my current Mir-3 that I use with my Kiev-6s bodies:





see the back, 12 blades on 2 irises:




the regular Mir-3 comes in 6 blades. According among others to the guys of "Periscop", the earlier 1957-1970 version for Salyut came also with 12 blades:
https://periscope.com.ua/obektivy/obektiv-mir-3v-3565

mine is a 1970 model:




the Kiev-6s started production in 1971 according to
https://ru.wikipedia.org/wiki/%D0%9A%D0%B8%D0%B5%D0%B2-6%D0%A1
and also according to Princelle (p. 225, 2nd english edition). (my Kiev-6s on the picture is 1972).
Which means that the Mir-3 bayonet-b that I have is either an early avatar for the P6 mount, or a hacked and modified bayonet-V for the Salyut.
The aperture pin on the back is missing, you can see, maybe because, the internals for the aperture setting don't easily take a pin.
For the 1st generation Salyut, lenses, like Industar-29 were with a preset ring, which is indeed not present on my lens, but you can see that maybe, if it was originally a bayonet-V for Salyut, the feature has been disabled, and the strip of leatherette to mask the ring added, after adjustment and installtion of the bayonet-b


anyway, i have found recently a bayonet-V version, from 1975 (all black). See, 12 blades on 2 irises, too:



I was thinking to buy it for my Salyut. But then I was also curious about other similar lenses.


PostPosted: Thu Jun 07, 2018 9:10 pm    Post subject: Reply with quote
This is just ONE iris with special iris blades, not two, sorry


PostPosted: Fri Jun 08, 2018 4:38 am    Post subject: Reply with quote
kds315* wrote:
This is just ONE iris with special iris blades, not two, sorry


good, so I have learnt/clarified something then Wink


PostPosted: Fri Jun 08, 2018 4:38 pm    Post subject: Reply with quote
but then, it's anyway interesting to know about these lenses that were versions of some common ones, but with double the blades. The Princelles doesn't mention for this one, the 12 blades variant. Also the 12 blades aren't technically one iris, this is a double iris (two superposed irises) on a single diaphragm. I should disassembly one in order to watch the mechanism. I guess I'll have to spend more time on runet...


PostPosted: Sun Jun 10, 2018 12:24 am    Post subject: Reply with quote
It's just the shape of the blades that make it look like it's a double iris, it's not, it's the L shape of the blade that does it.
http://forum.mflenses.com/why-voigtlander-nokton-35mm-1-4-get-2-iris-blade-t67665.html


PostPosted: Sun Jun 10, 2018 6:22 am    Post subject: Reply with quote
landstrykere wrote:
but then, it's anyway interesting to know about these lenses that were versions of some common ones, but with double the blades. The Princelles doesn't mention for this one, the 12 blades variant. Also the 12 blades aren't technically one iris, this is a double iris (two superposed irises) on a single diaphragm. I should disassembly one in order to watch the mechanism. I guess I'll have to spend more time on runet...


oh god please... yes, take one apart to see what it really is. I'm sorry...for the lens Wink


PostPosted: Sun Jun 10, 2018 11:33 am    Post subject: Reply with quote
It looks like a double at the first glance, but open and close it a few times and watch the blades closely and you can see it's the same blades appearing twice.


PostPosted: Sun Jun 10, 2018 5:00 pm    Post subject: Reply with quote
kds315* wrote:
yes, take one apart to see what it really is. I'm sorry...for the lens Wink


actually I had to take apart to the iris 70% of my P6 and Salyut lenses, in order to clean stuck blades, old solidified lubricant. Of course the Mir-3 may be something else.


PostPosted: Sun Jun 10, 2018 5:16 pm    Post subject: Reply with quote
blotafton wrote:
It looks like a double at the first glance, but open and close it a few times and watch the blades closely and you can see it's the same blades appearing twice.


I don't get it Rolling Eyes I see two layers of blades:



PostPosted: Sun Jun 10, 2018 5:56 pm    Post subject: Reply with quote
The blades are placed overlapping each other....


PostPosted: Sun Jun 10, 2018 10:18 pm    Post subject: Reply with quote
landstrykere wrote:
blotafton wrote:
It looks like a double at the first glance, but open and close it a few times and watch the blades closely and you can see it's the same blades appearing twice.


I don't get it Rolling Eyes I see two layers of blades:


You are only seeing the 2 strait sides of the L shaped blade at the same time, you may see the corner of the L near the last 2 smallest aperture openings.
one half of the blade forms what looks like one iris, and the other half of the blade forms what looks like the other iris, though it's really only one iris, the middle section in blue is usually hidden under the next blade, this is what makes it look like 2 irises.



PostPosted: Sun Jun 10, 2018 10:55 pm    Post subject: Reply with quote
Teemō wrote:
The Sony lens simply has a double aperture for producing the smoothest OOF area with rounded blades. It is also stepless.

Regarding the Minolta/Sony STF 135/2.8, the explanation for the double diaphragm is that Minolta wanted to design a lens with the smoothest bokeh. In order for the defocused highlights to be perfectly round when the lens was stopped down, the engineers needed an iris with many blades for a perfect circular aperture. Unfortunately, that kind of diaphragm with many blades is quite massive and couldn't be controlled by the camera's auto-diaphragm lever. So they decided to use two separate diaphragms:

- The first diaphragm is a regular lighweight iris with 9 circular blades that can be controlled by the camera ("automatic aperture"). It covers the range F/2.8-F/32 (T/4.5-T/32).
- The second diaphragm is a beautifully smooth stepless iris with 10 curved blades that can only be controlled through a dedicated ring on the lens. This diaphragm is only available for the range F/2.8-6.3 (T/4.5-6.7), i.e. the "smotth focus" range, because the apodization element is only effective below F/8.

Here's a picture of the two diaphragms, courtesy of Kurt Munger's website:



Cheers!

Abbazz


PostPosted: Sun Jun 10, 2018 11:37 pm    Post subject: Reply with quote




From http://forum.mflenses.com/dallmeyer-a-m-14in-356mm-f4-with-handmade-brass-m42-adapter-t29617,start,12.html


PostPosted: Mon Jun 11, 2018 2:33 pm    Post subject: Reply with quote
Lightshow wrote:


You are only seeing the 2 strait sides of the L shaped blade at the same time, you may see the corner of the L near the last 2 smallest aperture openings.
one half of the blade forms what looks like one iris, and the other half of the blade forms what looks like the other iris, though it's really only one iris, the middle section in blue is usually hidden under the next blade, this is what makes it look like 2 irises.





thank you for taking the time! Very clear.


PostPosted: Mon Jun 11, 2018 3:53 pm    Post subject: Reply with quote
wonderful, so all is clear now!

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