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08-24-2009, 12:41 PM   #16
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QuoteOriginally posted by richard64 Quote
I have an early version of the Super Takumar 55/1.8 (the aperture ring is 1.8 to 16 and in the 'wrong' direction, that is turn it away from the A/M switch to open up the aperture as opposed to all later pentax lenses where you turn the aperture ring towards the A/M switch to open up the aperture). It must be more than 45 years old. Looking through it at white paper, I can hardly see a difference, the paper is white. Looking obliquely at the front element I see a slight straw colour.

Richard
I have the same lens. depending on what year exactly it was manufactured it could be 47-49 years old. if yours (like mine) is the more common version lacking the 'half stop' markers, it is likely 47-48 years old.

08-25-2009, 08:26 PM   #17
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Here's the Super Tak 55mm f/1.8 versus the bare iPhone output (Flashlight application on full screen brightness) versus Super Tak 50mm f/1.4.



White balance was set in Lightroom to what the iPhone was putting out.
08-29-2009, 09:45 AM   #18
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QuoteOriginally posted by séamuis Quote
so then I wonder how many lenses Asahi optical manufactured with thorium? and why only the 50 1.4 is known today to have included it? I knew I wasn't seeing things with my 55's and that they indeed have some yellowing. very interesting info. I wish I had some more information oh Asahi Optical's use of this element in its lenses.
I have been doing a bit of research into the thorium glass and the yellowing. There is not that much information about that I have found yet but aparently Asahi used thorium glass in:
SMC Takumar 50mm f1.4 (Asahi Optical Co.)
Super Takumar 35mm f2.0, 50mm f1.5, 55mm f2 (Asahi Optical Co.)
Super Takumar 6x7 105mm f2.4 (Asahi Optical Co.)
Super-multi-coated Macro-Takumar (Asahi Optical Co.)
In addition, from my geiger counrter measurements the Super Takumar 50mm f/1.4 and the Super Takumar 55mm f/1.8 included it.
This information came from here: Thoriated Camera Lens (ca. 1970s)
The exact cause of the yellowing is unclear but it appears to be similar to the Solarization of glass (not the same as the Photographic Solarisation), see here Solarization - Wikipedia, the free encyclopedia.
It is not just glass whicg suffers from radiation damage yellowing. I have also observed it in Lucite bombarded with high energy electrons. After a couple of years on a shaded windowsil in not so sunny Wales the Lucite turned completely clear as well.
08-29-2009, 09:53 AM   #19
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QuoteOriginally posted by MattGunn Quote
I have been doing a bit of research into the thorium glass and the yellowing. There is not that much information about that I have found yet but aparently Asahi used thorium glass in:
SMC Takumar 50mm f1.4 (Asahi Optical Co.)
Super Takumar 35mm f2.0, 50mm f1.5, 55mm f2 (Asahi Optical Co.)
Super Takumar 6x7 105mm f2.4 (Asahi Optical Co.)
Super-multi-coated Macro-Takumar (Asahi Optical Co.)
In addition, from my geiger counrter measurements the Super Takumar 50mm f/1.4 and the Super Takumar 55mm f/1.8 included it.
This information came from here: Thoriated Camera Lens (ca. 1970s)
The exact cause of the yellowing is unclear but it appears to be similar to the Solarization of glass (not the same as the Photographic Solarisation), see here Solarization - Wikipedia, the free encyclopedia.
It is not just glass whicg suffers from radiation damage yellowing. I have also observed it in Lucite bombarded with high energy electrons. After a couple of years on a shaded windowsil in not so sunny Wales the Lucite turned completely clear as well.
thats incredibly interesting. especially the the macro. I find it very odd that they would use it in the later 1:2 macro but no the original 1:1 prest version. do you know the earliest lens they used it in? maybe that would explain it, as the macro-takumar preset was introduced in '62 if I remember correctly.

"50mm f1.5" was this meant to be 1.4? Asahi never manufactured a 50mmm 1.5.

08-29-2009, 10:28 AM   #20
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QuoteOriginally posted by séamuis Quote
"50mm f1.5" was this meant to be 1.4? Asahi never manufactured a 50mmm 1.5.
I guess this is probably a typo.
08-30-2009, 09:21 AM   #21
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QuoteOriginally posted by séamuis Quote
I have the same lens. depending on what year exactly it was manufactured it could be 47-49 years old. if yours (like mine) is the more common version lacking the 'half stop' markers, it is likely 47-48 years old.
Thanks for the info. Yes it it the one without the half stop markers. I've just noticed that even the A/M switch is reversed compared to my other Takumars - it is also much smoother in operation (my other Takumars tending to "clunk" a bit more when switching between A and M).

Did the other Takumars at the time have the aperture ring in the same configuratyion? I wonder why (from the photographer's position) it was decided that a clickwise turn to stop down was better. Or indeed, why do Asahi lenses have a focus ring that turns in the opposite direction to other lenses?



Richard
08-30-2009, 09:34 AM   #22
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as far as I know it was the only lens Asahi Optical ever produced with this 'backwards' aperture. and no, they never produced a lens that had a backwards focusing ring.


as an interesting side note, it would seem that I stumbled upon evidence that Asahi did indeed use thorium in at least this particular version of the 55.

I saw this on the same site I visit quite often for Takumar information, but never noticed until now.

"Razor-sharp, fully corrected, high speed standard lens, using rare earth glass, designed by top lens designers. Equipped with fully automatic diaphragm. Ideal for professional results.
"

Early Pentax Takumar Lenses
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