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01-25-2018, 06:19 PM   #1
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Takumar 200mm f3.5 M42 - Question about aperture ring

I purchased this classic Takumar lens based on the user reviews on this site.

The lens has two aperture rings at the front of the lens. One seems to limit the aperture that can be chosen to a range. The other actually sets the aperture.

Can someone explain why this was done and how best to use it?

Thanks in advance.

01-25-2018, 06:28 PM   #2
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Back in the day we did not have auto aperture as most folks grew up with. So when you looked through the viewfinder if the lens was stopped way down, like f/16 the viewfinder would be dark. So the two aperture rings were used to allow enough light in so you could focus.

The process was to set the first ring to the desired aperture and open the second ring. Focus the image and then close the second ring which would stop at the preset mark of the first ring.

You can simulate the same function on newer Takumars like the S-M-C versions by sliding the auto/man switch back and forth when used on a digital body.

---------- Post added 01-25-18 at 05:30 PM ----------

If you are new to Takumar lenses you might want to read this first: Troubleshooting and Beginner Help - PentaxForums.com
01-25-2018, 10:24 PM   #3
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QuoteOriginally posted by PaloAltoMark Quote
The lens has two aperture rings at the front of the lens. One seems to limit the aperture that can be chosen to a range. The other actually sets the aperture.

Can someone explain why this was done and how best to use it?
To elaborate on jatrax' comment, your lens has what is called a "pre-set" aperture mechanism*. One ring is used to set the desired aperture and the other ring is used as the actuator to do the actual opening/closing. There are many variations on the theme and such lenses were not uncommon for SLRs through the 1950s up and even into the early 1970s. Even today, some specialty lenses (e.g. tilt/shift) use this sort of arrangement where a coupled stop-down would be difficult to implement.

I currently own one pre-set lens, a Russian LZOS MC Jupiter-9 85/2 in M42 mount. Strangely enough, it was made less than ten years ago.

Here is a decent how-to page that include a pre-set Takumar as an example:

Preset Aperture Lenses – How They Work And Why You Need At Least One – 35hunter


Steve

* A good article for this site might be one about the four different types of aperture actuation and control mechanisms, manual, pre-set actuation, semi-auto actuation, auto-actuation, and auto-actuation with auto-control.
01-26-2018, 03:40 AM   #4
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QuoteOriginally posted by stevebrot Quote
* A good article for this site might be one about the four different types of aperture actuation and control mechanisms, manual, pre-set actuation, semi-auto actuation, auto-actuation, and auto-actuation with auto-control.
Yes this qq does crop up a few times...
We could ask member ProfHankD if he might be happy to pitch in with the piece he wrote for instructables.com

M42 Lens Aperture Control on Modern DSLRs: 3 Steps

01-26-2018, 06:33 AM   #5
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I used pre-set lenses for years when I bought my first Pentax (1958). Camera bodies that had no linkage for operating the aperture in a lens used several mechanisms: 1) double ring, probably the most common; 2) pull to lock, which I had on a 250mm tele (not Pentax brand), the aperture ring was a double piece, one knurled part could be pulled forward turned, then pulled back at the desired aperture, then the entire ring could be turned and would stop at maximum aperture on one side, desired shooting aperture at the other; 3) single-ring audible click stop, which I had on several longer telephotos (including a Pentax 300mm), essentially you counted clicks as you stopped the lens down after focusing at full aperture - not as difficult as you might think.

Among lenses that had obligatory preset or manually operated diaphragms were any and all T-mount system, regardless of manufacturer.

At the time I purchased my Asahi Pentax S there were two auto-aperture mechanisms on some cameras:

1) Exacta and Alpa (and later the earliest Topcon) used an external device on the lens itself, a protrusion that stuck out over a shutter release on the front of the camera body. As you pressed back on the button on the front of this protrusion the aperture closed slowly, it did not snap to taking aperture, then the button contacted the shutter release and triggered it. A very long-throw shutter release. Long telephotos did not have this mechanism. I think the longest lens equipped with this diaphragm device was Alpa's 180mm Alitar (hope I have that name correct)

2) A lever-cocking mechanism on the lens, You cock the lever, when the shutter release on the camera was pressed, the spring that was pulled back was released to stop down the lens. You had to recock the lens for each exposure, actually far less convenient than preset lenses which could be flipped wide-open to closed very quickly once you got the hang of it. The Asahi Pentax K, released at the same time as the "S" model, had this mechanism, but it was not incorporated into very many lenses.

3) I believe that the original Nikon F and Canonflex, introduced not too long after the Pentax S and K, were the first cameras with full, camera-body operated aperture open/close linkage. Even these manufacturers continued to use preset or manual diaphragms on long telephotos for decades. Some Canon "big glass" was focused with a bellows mechanism at the rear, which precluded any camera-diaphragm linkage. If I'm mistaken, someone will correct me soon enough
01-26-2018, 06:29 PM   #6
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Thanks to all for sharing your knowledge and experience. I greatly appreciate the help and look forward to using this lens.

I used to own an ME Super and an MX and miss them both. Small, well built cameras. Nothing today comes close to the build quality. Maybe I'll pick up an MX on ebay. Can't be that expensive nowadays.
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