Is the Asahi Pentax M42 Super Takumar 50mm f/1.4 radioactive: Does anyone have experience about the Asahi Pentax M42 Super Takumar 50mm f/1.4 being radioactive? I agreed to buy one on...

philklim Loc: Harrisonburg, Va.

Does anyone have experience about the Asahi Pentax M42 Super Takumar 50mm f/1.4 being radioactive?
I agreed to buy one on eBay, then started reading about it's radioactive possibilities on a google search.
I should have investigated the lens more thoroughly before pressing the "Buy it Now " button.
Thank you.
Phil

jethro779 Loc: Tucson, AZ

philklim wrote:

Does anyone have experience about the Asahi Pentax M42 Super Takumar 50mm f/1.4 being radioactive?
I agreed to buy one on eBay, then started reading about it's radioactive possibilities on a google search.
I should have investigated the lens more thoroughly before pressing the "Buy it Now " button.
Thank you.
Phil

If it is I should be glowing in the dark. I am told by fairly reliable sources that there is no more radiation in that lens than in the face of the old nite glow watches that everybody used to wear.

lamiaceae Loc: San Luis Obispo County, CA

philklim wrote:

Does anyone have experience about the Asahi Pentax M42 Super Takumar 50mm f/1.4 being radioactive?
I agreed to buy one on eBay, then started reading about it's radioactive possibilities on a google search.
I should have investigated the lens more thoroughly before pressing the "Buy it Now " button.
Thank you.
Phil

I'm aware of the issue. Find it rather amusing considering I own a number of old (Pentax) Takumar M-42 Screw Mount lenses. two 55mm f/1.8, and several other focal lengths, not the 50mm f/1.4. My understanding is that some slightly radioactive element was occasionally used (glass or coating?) during a few years in some batch runs for some models of Takumar lenses. But there was no tracking of this variation per serial number so there is probably no way to know for sure if you have one or not. Geiger Counter? The materials that I've read also state that there may be a slight yellowish discoloration of the coatings of these. But more yellow than what since many lens coating by all manufacturers sometimes look yellow-ish normally. It is not "hot" enough to fog film unless you left the lens sitting on the packaging for a long time. And would have no effect on a digital camera. If you are scared of it, I'll trade you for a couple others, 55mm f/1.8 and 35mm f/3.5 Takumar M-42 lenses.

suntouched Loc: Sierra Vista AZ

I have read both reports- the old Asahi lenses are radioactive and also that there is not enough radioactivity to worry about. So take your pick :) I have several of the old Asahi lenses and I don't worry about using them.

TriX Loc: Raleigh, NC

Unless you're going to spend a lot of time in very close proximity to it, I doubt you'd receive a noticeable dosage, even if it is an emitter. Of course, if you have a Geiger counter or scintillometer (you do have one don't you?😺), or know someone who does, you could always check it. I actually have a working civil defense yellow Geiger counter that I picked up cheaply and keep in my emergency cabinet along with a package of Iodine tablets. I'm not an alarmist or survivalist, but we do live ~20 miles from the Sharon Harris nuclear plant, which has one of the largest above-ground repositories of spent fuel rods in the eastern US😖.

twowindsbear

Just take the lens with you the next time you fly. TSA will tell you, in no uncertain terms, if your lens is radioactive. You may even get to meet a bunch of new friends, too.

suntouched Loc: Sierra Vista AZ

twowindsbear wrote:

Just take the lens with you the next time you fly. TSA will tell you, in no uncertain terms, if your lens is radioactive. You may even get to meet a bunch of new friends, too.

That's funny!!

philklim Loc: Harrisonburg, Va.

New friends from TSA I could do without.

Phil

blackest Loc: Ireland

philklim wrote:

Does anyone have experience about the Asahi Pentax M42 Super Takumar 50mm f/1.4 being radioactive?
I agreed to buy one on eBay, then started reading about it's radioactive possibilities on a google search.
I should have investigated the lens more thoroughly before pressing the "Buy it Now " button.
Thank you.
Phil

Yes i think so I have a couple

https://petapixel.com/2012/10/11/a-look-at-the-radioactivity-of-old-manual-lenses/

This puts the “6hrs/day for a month” usage at about the same as getting a chest X-ray […] Or to put it another way, using the lens six hours a day for a year would be the same as taking three round-trip flights from one US coast to the other in that year. Not completely trivial, but not something people normally stress about. And that’d be really heavy usage.

The articles indicate that exposure to the eye might be a greater concern than overall dosage, particularly if you happen to have thorium in an eyepiece […] So you might decide to spend a little less time holding the camera right to your eye than you might otherwise.

Assuming (based on the reading) that looking through the viewfinder is very roughly an order of magnitude greater exposure than the general usage, looking through the viewfinder for an hour is about 1µSv — equivalent to getting an arm x-ray.

marki3rd Loc: Columbus, Indiana

philklim wrote:

Does anyone have experience about the Asahi Pentax M42 Super Takumar 50mm f/1.4 being radioactive?
I agreed to buy one on eBay, then started reading about it's radioactive possibilities on a google search.
I should have investigated the lens more thoroughly before pressing the "Buy it Now " button.
Thank you.
Phil

When first released in 1964, the Pentax 50mm f/1.4 M42 Screw Mount Lens had 8 Elements. This lens was designed to be a world beater against the best lenses Germany had to offer at the time, and it was successful. However, it was very expensive to manufacture so Pentax soon redesigned it to a less expensive to manufacture 7 Element version which had a mildly radioactive element in the glass of one of the lenses elements. This very mild radioactivity had the effect of turning that lens element yellow(ish) over an extended period of time. Some users shooting film actually liked that (look at the yellow filters often used with film). Exposing those lenses with the yellowing to UV Light removes the yellowing. This could be accomplished using sunlight or UV Lighting if a user preferred a non-yellow lens.

The informed scientific opinion is that the very mild radioactivity, which is only detectable with sensitive measurement equipment very close to the lens, is not of any reasonable concern.

marki3rd Loc: Columbus, Indiana

blackest wrote:

Yes i think so I have a couple br br https://pet... (show quote)

There is no Thorium in the eyepieces of Pentax Cameras. That is really stretching the concerns since the eye when looking through the camera's viewfinder is not close enough to the lens to be of particular concern.

SharpShooter Loc: NorCal

philklim wrote:

Does anyone have experience about the Asahi Pentax M42 Super Takumar 50mm f/1.4 being radioactive?
I agreed to buy one on eBay, then started reading about it's radioactive possibilities on a google search.
I should have investigated the lens more thoroughly before pressing the "Buy it Now " button.
Thank you.
Phil

Phil, it had been 50 years since I even looked at mine. Upon reading your post I pulled mine out and looked at it.
It is nothing but a big hunk of lead now!!! So you are correct!
That lens had a short half-life.
I hate it when that happens!!!!!! LoL
SS

blackest Loc: Ireland

marki3rd wrote:

There is no Thorium in the eyepieces of Pentax Cameras. That is really stretching the concerns since the eye when looking through the camera's viewfinder is not close enough to the lens to be of particular concern.

That doesn't mean other camera's couldn't have but it is a reasonable thing to consider. To be fair the worst thing you could do is hold the lens up to your eye.

In reality it's a small risk, but really we are about as likely to be triggered from background radiation as a lens possibly more so. As the article says it was more hazardous making the lenses. They did tend to help light bend better and reduce CA in photo's. The thorium glass has great optical properties which is why it was used.

n3eg Loc: West coast USA

I have one, and yes, it is radioactive. More radioactive on the back end than the front, according to my tests.

rook2c4 Loc: Philadelphia, PA USA

n3eg wrote:

I have one, and yes, it is radioactive. More radioactive on the back end than the front, according to my tests.

Did you use a geiger counter?