[FHPhotographer]

As with this forum, I posted my questinon about a Super Takumar f/2 I saw for sale and asked about the yellowed lenses. This is the surprising reply:

The yellowing could be the standard Pentax coating. Especially the Super-Multi-Coating has a rather golden colour to it. If it really is a mis-coloured element, it indeed means it is radioactive.
I other places mentioning the Pentax 35/2 being affected, so not only the 50/1.4 (where it seems more common or pronounced). A friend and me tested the radiation of my 50/1.4 and our findings were pretty in-tune with those:
Warning, radioactive lenses!
IMO it is not something to take light-heartedly.
Here's a link with background info:
Thoriated Camera Lens (ca. 1970s)

I assume this old news to Takumar users, but I thought I'd share it anyway,
FHPhotographer

[stevebrot]

Just a bit of clarification:

• Yellowish surface reflection = coating color
• Yellow cast when viewing a white background through the lens = discolored elements

One explanation I heard regarding the yellow discoloration is that it is often the result of a chemical changes in the balsam cement used to glue the lens groups together. This chemical change may be due to radiation from thorium glass or some other cause and may be remedied by exposing the glass to UV light. Here is a link regarding the UV treatment:

orly going thirty: The Blue Light

If you suspect you have a radioactive lens, you might be able to have someone pass a Geiger counter over it.

Note that radiation is probably not the only possible cause of yellowing. I have a Rikenon 50mm from the late '60s that is also yellowed somewhat, though I have never seen that brand on the radioactive list.

Steve

(Glowing in the dark...)

[jamonation]

That second link points to a few studies that make calculations about m/rem exposures at 18% thorium content and 20 hours exposure per week. I dunno about you, but I can only dream of the day I'd have that much time to use my 50mm Super Takumar, and if I were using it that much all the time I'd be more worried about getting hit by a bus out in the street while taking a photo than cataracts

edit:nm, steve's post explains it better

[troywhite]

I assume this old news to Takumar users, but I thought I'd share it anyway,
FHPhotographer

Yes.... they are extremely dangerous, so please package up any you have and ship them to my postal address and I'll take care of them for you for no charge of course

:P

[pingflood]

I too volunteer to dispose of these dangerous, dangerous lenses.

If you love your family, do not keep radioactive glass around! And you do love your family, don't you?

[jocko_nc]

I have atomic lenses... Sweet!

How old school is that?

[huqedato]

I've totally cured my S-M-C Tak 50/1.4 from yellowing, this summer, using sun exposure (it tooks about four weeks). So, is it still radioactive ?
I've been using this lens for about twenty yrs so I am going to die ?

Seriously, some say that is a relation between the radioactive element and the yellow cast... believe it or not ? Read here and here please!

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Last edited by huqedato; 09-17-2008 at 05:51 PM.

[lithos]

Just a bit of clarification:
Note that radiation is probably not the only possible cause of yellowing. I have a Rikenon 50mm from the late '60s that is also yellowed somewhat, though I have never seen that brand on the radioactive list.

Steve

(Glowing in the dark...)

I heard some Riks were, back in the day. But now we've found hippie-glass alternatives. I think it was one of the best ways to get the opticals properties the lens makers desired, and it was cheaper than going out and looking for meteorites.

Don't quote me on the radioactive Riks, though. It's a very vague memory.

They way to test is, apparently, is to put the lens down on a piece of Polaroid film, or even just normal black-and-white film (in total darkness, of course!) and leave it in the dark for a few hours or so, and then develop. If there's fogging on the film, it's radioactive - and that's pretty much how they measured exposure to radioactivity, a little badge with bits of film on it.

There's probably not much concern to be had with radioactive glass. Just as long as you resist the urge to walk around with the lens shoved down your undies. Even with modern glass that's still not a good idea, because they kick you out of the Christian bookstore pretty fast.

[wlank]

In addition to the radioactive problem with the various Takumar lenses there is another problem which is even more dangerous.

In another thread a few months back a user related that he was was changing from an M42 mount to a K mount while standing on the platform of a train station. He dropped th mount adapter, it rolled off the platform, and ended up by the tracks. He jumped down retrieved the mount adapter, and returned to the platform.

The conclusion which I have come to is that in addition to having your eyeball shrivel up and fall out along with the potential loss of teeth from radiation exposure, you also have the possibility of getting run over by a train. These lenses are dangerous and should only be used by a professional. Send all your Takumar lenses to Mike Cash. Mike is really "Mr. Takumar" around here and he will know what to do. You can't be too careful.

[Fireball]

Hey, at least it can be a cheap alternative to a vasectomy.

[stevebrot]

Hey, at least it can be a cheap alternative to a vasectomy.

Ummm...And just what is that you do with your lenses?


Steve

[stevebrot]

I heard some Riks were, back in the day. But now we've found hippie-glass alternatives. I think it was one of the best ways to get the opticals properties the lens makers desired, and it was cheaper than going out and looking for meteorites.

Don't quote me on the radioactive Riks, though. It's a very vague memory.

Given that a Tomioka-made Yashinon is on the "hot" list and that the older Rikenons are reputed have been made by Tomioka, it is not too much of a stretch.

Steve

[FHPhotographer]

In addition to the radioactive problem with the various Takumar lenses there is another problem which is even more dangerous.

In another thread a few months back a user related that he was was changing from an M42 mount to a K mount while standing on the platform of a train station. He dropped th mount adapter, it rolled off the platform, and ended up by the tracks. He jumped down retrieved the mount adapter, and returned to the platform.

The conclusion which I have come to is that in addition to having your eyeball shrivel up and fall out along with the potential loss of teeth from radiation exposure, you also have the possibility of getting run over by a train. These lenses are dangerous and should only be used by a professional. Send all your Takumar lenses to Mike Cash. Mike is really "Mr. Takumar" around here and he will know what to do. You can't be too careful.

This is irony, right? Gee, I like it when y'all get clever. I have to work to keep up and at my age that sort of thing is good for the old noggin.
Thanks again,
FHPhotog

[straightshooter]

Send all your Takumar lenses to Mike Cash. Mike is really "Mr. Takumar" around here and he will know what to do.

Having worked for an airline for 34 years, I received recurrent training every year in the handling of dangerous goods including radioactive materials. I firmly believe that, Mike's experience aside, I am the most qualified to handle these items. For a small yearly retainer, I will correctly store these lenses for you so that your family will be safe.

Hey Bill, I see you got the 105. How do you like it?

CW

[Fl_Gulfer]

Hell I'm dieing anyway, so who cares.....