Super Multi-Coated Takumar 50/1.4 Yellowing

Ryan Oliveira · Nov 28, 2020

By that I mean that I use my camera with the lens every day, sometimes I take the lens off just to clean it but that's about it...

AgX · Nov 28, 2020

Ryan, you overlooked the link I posted in this respect.

Thus here again:
A state institute on radioactivity once assumed the radiation strain by using an SLR with Takunar lens for 100h/year at 1/10 of the natural radiation.
But that also means, putting the plain lens under your pillow will give other results.

Ryan Oliveira · Nov 28, 2020

I think I missed your post. And that seems like not that much radiation for a lens, but I'm still concerned. 100 hours is not much either, if someone is using it regularly for a few hours a day (which I'm not, but not uncommon for many photographers), it would reach this dose in a couple of months or even a month.
I shouldn't worry too much, but even if it was a higher level (let's say, equal to 1 year of backround radiation instead of 1/10), it's still not enough to be "seriously dangerous", I mean, to the point that it's not ideal to use it anymore

Donald Qualls · Nov 29, 2020

"Not much radiation for a lens" would be background level, or perhaps a little below since the overall background count has gone up a little over the past seventy-five years (due to nuclear testing and accidents) and many of our lenses are old enough to have been made before that increase.

Still, the radiation from a thoriated lens element is comparable to that from a lantern mantle made before thorium salts were replaced in that application (I don't recall with what); the dust collector in a tungsten grinder for sharpening TIG electrodes is surely a larger hazard. Those electrodes are often thoriated, as it makes arc starting easier, and after several years of use in an active welding shop, one of those machines might collect a couple pounds of thoriated tungsten dust (I've refused to work on those machines where I repair power tools, because we don't have the equipment to either check for radiation, or protect against either the thorium or the tungsten dust itself).

Ryan Oliveira · Nov 29, 2020

So, in conclusion, can I safely keep my lens near me without being too dangerous ?

AgX said that it's 1/10 of backround radiation per 100 hours of use/year, what does this acually mean in terms of Rems ?
I've read that about 0.62 Rem is the amount of radiation a person receives yearly and about half of that is backround radiation. That is 620 millirems.
The lens emmits around 1/10 of that per 100 hours, or about 62 millirem/0.062 Rem.
The maximum SAFE dose for an adult early is about 5 Rem, or 5000 milirem. Thats 16 times the backround radiation.
I think it's safe to assume that it doesn't pose much more risk than flying on an airplane many times a year or just receiving natural backround radiation.

Ryan Oliveira · Nov 29, 2020

Even if it emmited higher levels, it would still be way within the limits of safe yearly exposure.

RLangham · Nov 29, 2020

Ryan Oliveira said:
So, in conclusion, can I safely keep my lens near me without being too dangerous ?

AgX said that it's 1/10 of backround radiation per 100 hours of use/year, what does this acually mean in terms of Rems ?
I've read that about 0.62 Rem is the amount of radiation a person receives yearly and about half of that is backround radiation. That is 620 millirems.
The lens emmits around 1/10 of that per 100 hours, or about 62 millirem/0.062 Rem.
The maximum SAFE dose for an adult early is about 5 Rem, or 5000 milirem. Thats 16 times the backround radiation.
I think it's safe to assume that it doesn't pose much more risk than flying on an airplane many times a year or just receiving natural backround radiation.

Do you smoke? Or drink? I do both, like a man years older than me. Both will likely give you cancer faster than that extra 0.062 millirems. There are actually radioactive components in tobacco smoke.

And it's a stochastic phenomenon. Radiation damages molecules. It's completely random whether, in any given amount of exposure, some of those molecules will be important segments of your chromosomes or for instance the cell walls in dead skin cells. It's not like the cancer we all eventually get is a predictable phenomenon, because a million such random phenomenon dictate whether the DNA damage that causes cancer will happen in a certain place at a certain time.

Ryan Oliveira · Nov 29, 2020

Well, I think I already know the answer to question "whether or not it's safe".
Just wanted to say thay I'm keeping my lens and I should be fine, given the amount of time I actually use it. Thanks to all of you that replied !

Donald Qualls · Nov 29, 2020

I've had my radioactive Super Takumar 50mm f/1.4 since 1981. Last I checked, there's nothing wrong with me that could be attributed to radiation (especially not that amount). Due to a car accident, followed by discovery of kidney stones, I had three CAT scans and four flat x-rays in 2019, plus an unknown amount of exposure to a fluoroscope (equivalent) during the actual lithotripter procedure; I also had a fluorscopy and several flat x-rays during a "swallow study". Those most likely exceeded the lifetime exposure I'll get by keeping that lens, which has spent most of its time on a shelf or in a box, for another forty years (in the unlikely event I live that long).

Ryan Oliveira · Nov 29, 2020

I see your point. I'm young, 16, so most likely I wasn't exposed to this amount of radiation in my lifetime.
I really didn't meant to get serious about this topic, but it made me less anxious than I was before. Thanks Donald !

AgX · Nov 30, 2020

Well Ryan, you likely are one of our youngest members. Great to learn about that.

Kodachromeguy · Nov 30, 2020

Ryan Oliveira said:
I'm young, 16, so most likely I wasn't exposed to this amount of radiation in my lifetime.

Many of us old geezers received varying exposures in the 1950s and 1960s from:
1. Atmospheric testing of nuclear weapons.
2. Dental and body X-rays in the era when the machines used high doses compared to today (and the doctor was quick to prescribe an X-ray for almost anything).
3. Unknown dosage from radon in houses built on certain geological terrains.

We also were exposed to innumerable hazardous chemicals:
1. Lead in cities from use of leaded gasoline.
2. Asbestos from pipe and other insulation.
3. Second-hand smoke when almost everyone smoked everywhere, including grocery stores, doctors offices, hospitals, and airplanes.
4. Atmospheric waste from refineries and other heavy industries.
5. Mercury from the emissions of coal-fired power plants.

However, we were largely spared from two vile food products that are now imposed on us:
1. High-fructose corn syrup (have you seen what Americans look like today compared to 1970? It's disgusting.)
2. GMO-modified crops.

AgX · Nov 30, 2020

Kodachromeguy said:
Many of us old geezers received varying exposures in the 1950s and 1960s from:

2. Dental and body X-rays in the era when the machines used high doses compared to today (and the doctor was quick to prescribe an X-ray for almost anything).

I like to add X-raying children feet inside shoes at shoe stores, to control on fit. Such devices were legal very long in Europe.

Dan Fromm · Nov 30, 2020

AgX said:
I like to add X-raying children feet inside shoes at shoe stores, to control on fit. Such devices were legal very long in Europe.

In the US, too.

albada · Dec 1, 2020

And cars had no seatbelts.
The radioactive Super Tak lens is safe in comparison.
Regarding those bad old days, I like to say that "safety had not been invented yet."
I'm thinking of hood ornaments that would tear up a pedestrian, and a conical horn-button that would spear you in the heart in a wreck. Unbelievable.
Mark Overton

Donald Qualls · Dec 1, 2020

albada said:
\ a conical horn-button that would spear you in the heart in a wreck. Unbelievable.

And unnecessary -- the old solid steering columns did that regardless what was on the driver end.

reddesert · Dec 1, 2020

As discussed above, I don't think normal photographic use of this lens is a health hazard. See the link I posted earlier https://www.orau.org/ptp/collection/consumer products/cameralens.htm for more details of the expected intensity (the link is to the Oak Ridge Lab online museum of radioactive consumer products, so an actual health physics source).

It's the same stuff as in thoriated mantles for camping lanterns, although there's a lot more thorium in a lens - see https://www.orau.org/ptp/collection/consumer products/mantle.htm, there's perhaps 0.25 g of thorium in a mantle, and a lens with one or a few elements of 10-20% thorium probably has 5-20 g of thorium.

However, if you're going to keep it in your room, and be exposed to it continuously, I would store it in a heavy box, like a wood or metal box. It doesn't have to be anything special like lead. Nearly any material will attenuate beta radiation if there's enough of it, like several mm thickness. This is probably overkill since the hazard is small, but it's also an easy precaution.

Ryan Oliveira · Feb 1, 2021

However, if you're going to keep it in your room, and be exposed to it continuously, I would store it in a heavy box, like a wood or metal box. It doesn't have to be anything special like lead. Nearly any material will attenuate beta radiation if there's enough of it, like several mm thickness. This is probably overkill since the hazard is small, but it's also an easy precaution.[/QUOTE]

My camera (Pentax Spotmatic for that matter) is now mounted with the lens, fitted on it's leather case, and sitting on a shelf about 5 feet high, and 7 feet away from my bed.
If most of the radiation comes from the back element, it's facing the concrete wall, and not much of it comes through the front (only 2uSv)

Donald Qualls · Feb 1, 2021

And a couple meters of air is just as good a shield against alpha particles as a shoe box, not to mention the inverse square law is your friend in this case.

Ryan Oliveira · Feb 1, 2021

That's what I was thinking, 2 meters of air is enough to block it.
I was so worried about the lens, now I don't take it out anymore, just when I want to use the camera.

Ryan Oliveira · Feb 1, 2021

When it was directly over my bed I was worried, now that I moved it away it's better.

Donald Qualls · Feb 1, 2021

I've got a Super Takumar with thoriate element that I've had for forty years. It's fine. Don't crush it and swallow or inhale the glass fragments (that would be bad with any glass). Otherwise, the lens itself is adequate shielding.

Super Multi-Coated Takumar 50/1.4 Yellowing

Privacy & Transparency

Privacy & Transparency