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03-13-2012, 02:47 PM   #16
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QuoteOriginally posted by John Poitiers Quote
Pas de problème ... et à plus tard (ou "A+"), J
Vous êtes trop aimable. -R

03-13-2012, 02:51 PM   #17
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QuoteOriginally posted by stevebrot Quote
That is what I was thinking. A yellowish 55/1.8 is not impossible, but the yellowing is more typically associated with the thoriated (radioactive) lenses of the period and the 55/1.8 lacks the exotic glass.


Steve


(The yellowing of the thoriated lenses is due to radiation-induced degradation of the balsam cement used to glue the lens elements together. No radiation, less chance of degradation.)
I'm not so sure that Asahi Optical never used any thoriated glass in any of the 55's. the truth is we don't actually know what Asahi Opt. did and didn't do, and while I believe there is no known official documents or otherwise showing that they did or didn't, there are a number of people who have had examples of 55's with what have at least looked like yellowed glass. I would say, we should never rule out the possibility that at least there are some 55's out there with thoriated glass, unless someone can prove pretty assuredly that Asahi Opt. never used any thoriated glass elements in any lenses other than the non-8 element 50mm 1.4's.
03-13-2012, 03:06 PM   #18
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Older posts ...

Just FYI - just found this in an older thread ...

Thoriated Camera Lens (ca. 1970s) - According to this source the Super-Tak 55 f2 is radioactive ...

Plus the following post: Posted by MattGunn on 08/2009

Copied from A post I made in this thread:
Super Takumar 135mm f/3.5 and Super Takumar 55mm f/1.8


"I have the Super Tack versions of the 50mm f/1.4 and a 55mm f/1.8. They were both yellow when I got them, the 1.4 was a bit worse but they both have about the same level of radioactivity as measured with my cheep geiger counter. It appears that it is the rear lens element that is radioactive so if you intend to leave one in the sun for UV treatment then it should have the back end facing up.

The thorium was added to the glass to raise the refractive index and lower the dispersion of the glass so these lenses used the LD glass of their day. The radioactice decay slowly turns the glass yellow but UV treatment anneals the yellowing out of the glass turning it clear again. The type and level of the radioactivity from these lenses is not really dangerout but it's best not to keep one in you pocket for long periods...
I also have the 135mm f/3.5 and the 300mm f/4 and neither of these are radioactive."

To elaborate on the sunbathing, It is the UV in the sunlight which bleaches the yellowing and leaves the lens clear. I left mine on a windowsil for about 6 months over the summer (we don't see the sun much here in wales) and this removed much of the yellowing. However window glass absorbes a lot of the UV so this will probably have slowed the process. A UV exposure box would be ideal but a few sessions at a local tanning salon may be worth a try
03-13-2012, 03:08 PM   #19
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QuoteOriginally posted by John Poitiers Quote
Just FYI - just found this in an older thread ...

Thoriated Camera Lens (ca. 1970s)

Plus the following post: Posted by MattGunn on 08/2009

Copied from A post I made in this thread:
Super Takumar 135mm f/3.5 and Super Takumar 55mm f/1.8


"I have the Super Tack versions of the 50mm f/1.4 and a 55mm f/1.8. They were both yellow when I got them, the 1.4 was a bit worse but they both have about the same level of radioactivity as measured with my cheep geiger counter. It appears that it is the rear lens element that is radioactive so if you intend to leave one in the sun for UV treatment then it should have the back end facing up.

The thorium was added to the glass to raise the refractive index and lower the dispersion of the glass so these lenses used the LD glass of their day. The radioactice decay slowly turns the glass yellow but UV treatment anneals the yellowing out of the glass turning it clear again. The type and level of the radioactivity from these lenses is not really dangerout but it's best not to keep one in you pocket for long periods...
I also have the 135mm f/3.5 and the 300mm f/4 and neither of these are radioactive."

To elaborate on the sunbathing, It is the UV in the sunlight which bleaches the yellowing and leaves the lens clear. I left mine on a windowsil for about 6 months over the summer (we don't see the sun much here in wales) and this removed much of the yellowing. However window glass absorbes a lot of the UV so this will probably have slowed the process. A UV exposure box would be ideal but a few sessions at a local tanning salon may be worth a try
Absolument excellent. Je vous remercie pour les informations complémentaires. -R

03-13-2012, 05:55 PM - 1 Like   #20
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QuoteOriginally posted by séamuis Quote
I'm not so sure that Asahi Optical never used any thoriated glass in any of the 55's. the truth is we don't actually know what Asahi Opt. did and didn't do, and while I believe there is no known official documents or otherwise showing that they did or didn't, there are a number of people who have had examples of 55's with what have at least looked like yellowed glass. I would say, we should never rule out the possibility that at least there are some 55's out there with thoriated glass, unless someone can prove pretty assuredly that Asahi Opt. never used any thoriated glass elements in any lenses other than the non-8 element 50mm 1.4's.
I researched this matter several years ago and based my comment partially on that research and partially on what I have been by various camera buffs, repair people and such. If the 55/1.8 has the yellowing problem, it was new to me.

On the other hand, I have long suspected that the lists (including the one linked several comments above) are far from complete. I just did a little Google work and was surprised to find videos of people testing lenses that I would never have dreamed were radioactive. Based on that search it appears that these lenses were quite common. The big surprises? How do these sound:
  • Yashinon DX 35/1.8 (on Electro 35 CC)
  • Various Super-8 movie cameras
  • Yashinon DS/DX 50/1.4/1.7
  • Mamiya/Sekor 55/1.4
  • Leitz Summicron 50/2 (collapsible ca. 1953)
  • A plethora of Canon FD/FL fast 50s
  • EBC Fujinon 50/1.4
  • Various Zeiss Jena
...and yes...at least two (SMC and S-M-C) Takumar 55/1.8.

It almost makes me want to get a cheap geiger counter and head down to check out the shelves at the local used camera places. Seriously though, I own a couple of lenses (non-Pentax fast 50s from the late 60s and my Jupiter-8 in Contax/Kiev) that have a yellowish cast that I would sort of like to test just to satisfy my curiosity.


Steve

Last edited by stevebrot; 03-13-2012 at 06:50 PM.
03-13-2012, 06:23 PM   #21
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I have a 55mm f1.8 in a south exposure window right now, wrapped in aluminum foil with the rear lens exposed to the UV from the sun. It is getting progressively less of a yellowish cast as the days pass. While I can't state with any certainty that I'm dealing with thoriated glass, I can state that the cheapest method of treating thoriated glass is working.
As an aside, I have read that radioactive materials in the assembly of the AF 1.7 TC are the limiting factor in it being retailed in North America.
03-13-2012, 06:31 PM   #22
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Eirc advised at one time that it was the balsam cement between the elements that turned yellow, not the glass. It clears so rapidly under a black light (I still had a flourescent about 12" long from the 70s that works well and within 48 hours) so the thin cement layer make sense.
The version 1 Leica Summicron is known for yellowing also, and sometimes the M3 viewfinder becomes yellowed - which also used balsam cement.
03-13-2012, 06:40 PM   #23
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QuoteOriginally posted by TomB_tx Quote
Eirc advised at one time that it was the balsam cement between the elements that turned yellow, not the glass. It clears so rapidly under a black light (I still had a flourescent about 12" long from the 70s that works well and within 48 hours) so the thin cement layer make sense.
The version 1 Leica Summicron is known for yellowing also, and sometimes the M3 viewfinder becomes yellowed - which also used balsam cement.
Also makes sense. The same 'glue' that has held microscope slide cover glass on for decades.

03-13-2012, 07:19 PM   #24
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QuoteOriginally posted by John Poitiers Quote
Pas de problème ... et à plus tard (ou "A+"), J
Or, as we say around here, Pas de sweat.
03-13-2012, 07:20 PM   #25
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I have one of the Ikea LED lamps and used it on a Super-Multi-Coated 50mm f1.4 and a Super-Takumar 35mm f2 that were both yellowed. After about three or four days each, they were clear.

-Joe-
03-13-2012, 08:11 PM - 1 Like   #26
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Thoriated Camera Lens (ca. 1970s)

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.)
03-14-2012, 02:16 PM   #27
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LOL ... "sweat" ?!

QuoteOriginally posted by John Poirier Quote
Or, as we say around here, Pas de sweat.
Bonjour John Poirier,

... or as it's said here sometimes ... MDR (mort de rire) !

A+, J Frog

PS - Sorry that I selected my forum name which is so close to your name ... pure random chance.
03-14-2012, 02:21 PM   #28
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Merci ...

QuoteOriginally posted by jac Quote
I have a 55mm f1.8 in a south exposure window right now, wrapped in aluminum foil with the rear lens exposed to the UV from the sun. It is getting progressively less of a yellowish cast as the days pass. While I can't state with any certainty that I'm dealing with thoriated glass, I can state that the cheapest method of treating thoriated glass is working. ... .
Bonjour jac,

Thanks for your post ... Good to know that I'm not alone. Maybe good old fashion UV's at first, then maybe later buy/try the IKEA LED lamp ...

Salut, J
03-14-2012, 02:28 PM   #29
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Typo

QuoteOriginally posted by riff Quote
Thoriated Camera Lens (ca. 1970s)

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.)
Just FYI again,

Read last night someone somewhere that stated the 50mm f1.5 was probably a typing error ... obviously it's f1.4.

A+, J

Last edited by Jean Poitiers; 03-14-2012 at 11:44 PM.
03-14-2012, 04:08 PM   #30
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I once owned a Super Takumar 35mm f/2.0 lens, the later version with 49mm filter thread.
The lens elements had turned so deeply amber I dared not use it for color slides.
But it was fine for use with black and white film - a built-in yellow filter of sorts...

Chris
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