Radioactive eyepieces?

<p>Hi.</p>

<p>I've seen what webpages I could find on the issue of radioactive lenses and the general conclusion seems to be that with the normal patterns of usage they get today, they're not really dangerous (sparsely used, not touched directly, etc). Everyone cautions against radioactive eyepieces, tho. But I haven't seen a single example of a radioactive eyepiece referred. Does anyone here know of any? I haven't yet understood if radioactive materials were limited to a few brands/models/price ranges, or if they were used regularly.</p>

<p>I've also read that radioactive materials ceased to be used in 1970, and then that some early FD lenses (FD was introduced in 1971) are radioactive. Does anyone know of a page where one can find the dates of introduction of old lenses? Wikipedia is nice for EF (supposing one can believe it), but has little info on FD.</p>

<p>Don't think any camera eyepiece used glass with rare earths in the mix. However there were some military surplus tank gunsight eyepieces used as wide field eyepieces by hobby astronomers in the 60's to 80's that were said to have thorated glass and be radioactive. <br>

I have a 50mm f1.4 Super Takumar that has quite a bit of staining in the elements but only use it for B&W so no problem with any mild radioactivity or resulting color cast. </p>

<p>There would be no reason to go to the expense of Thoriated glass in the viewing system of a camera, since it doesn't need to be super sharp. <br>

Maybe some old microscope optics (where performance is much more important) might have been radioactive.<br>

It is illegal in the US to manufacture eyepieces using radioactive glass, as it is a real safety issue.</p>

<p>Most of the lenses which were manufactured with radioactive compounds in them exhibit less radioactivity than old watches which were (pretty much) continuously worn against one's skin for long periods of time. I have never seen anything in the medical journals which indicated persons being affected by use of those lenses...although we know the harmful effects from long term exposure to higher levels of those radioactive elements. If eyepieces are identified which were manufactured with radioactive elements (I don't know of any and did work for a long time in a microbiology lab), I would merely limit my eyes' exposure to under 6 hrs/day.</p>

There is NO significant danger.

.....

"Luckily for us some studies on these lenses has been done. Regulation of these kinds of devices falls to the Nuclear

Regulatory Commission (NRC), and they have published some pretty detailed studies of consumer products containing

radiation. NUREG-1717 (massive pdf here) has a part that covers Thorium lenses specifically (page 3-289 for those

interested).

 

Here's what they found:

 

Taylor et al. (1983) measured the absorbed dose rate at the back of a camera and the thorium content of the lens. The

thorium in the lens was estimated to be 13 kBq (0.36 Ci). Using the 3–290 methodology described in Appendix A.4 for

sources close to the body, the dose rate at 10 cm depth in the body was determined to be 1×10-4 mSv/h (0.01 mrem/h).

A serious outdoor photographer is assumed to spend 30 days/yr in the field (average photographers-10 days/yr) and to

carry a camera next to the body for 6 hours per day during that time. This exposure time should be conservative for most

photographers. Based on the assumed exposure time and the absorbed dose rate, the annual EDE would be 0.02 mSv (2

mrem). For an average photographer the EDE would be 0.007 mSv (0.7 mrem)

Note that 0.007 mSv is 0.2% of what you get annual from normal background radiation (3 mSv).

 

A more pertinent question might be what the dose rate to the eye is. Radiation exposure can lead to cataracts, and of

course a camera lens is going to be very close to one's eye. From the same publication, they measured the dose rate at

the surface of the camera lens to be 0.48 mrad/h, or about 5 micro-Sv/hr. The dose limit to the lens of the eye for

members of the public is 15 mSv per year, so you would need to hold this lens against your eye for 3,000 hours to exceed

that. With the lens attached to a camera, the dose rate dropped by a factor of 5 (due to blocking the electrons and

alphas).

 

At this level, one couldn't exceed the dose limit even if they continually held the camera to their eye for an entire year.

 

Also note that dose limits to members of the public are already pretty conservative in terms of preventing effects.

So to summarize, there is almost no way to exceed the dose limits while using a camera of this type. Furthermore, the

radiation you would receive is only a small fraction of the background radiation."

 

Source:

<p>Ah, Benoit,<br /> Actually having <em>facts</em> is sooo 20th century.</p>

<p>Nowadays, we <em>feel</em> our way to truth. I think somebody or other once called it the "triumph of the will."</p>

<p>Thanks for trying though.</p>

<p>@OP</p>

<p>If you live near the border, please take the optic/s in question with you and they are able to analyze the limits and limitations. Just make sure so that you don't trip the detectors there :>). Believe me, it's not difficult to do.</p>

<p>Les</p>

<p>It sounds like Benoit had to convince a significant other to let him keep a radioactive lens - and made a way better argument than my "but it makes my pictures look pretty" plea. I miss that Super Takumar.......</p>

<p>So it would be hard to get poisoned from a lens, and there are no generally known eyepieces that are dangerous either. One might as well not leave home for fear of UV rays.</p>

<p>Most people during their lifetimes probably ingest more radioactivity thru the meat and vegetables they eat and milk they drink, than they would pick up from using these lenses.</p>

<p>Not to speak of the radiation they get while sitting inside a plane at 30,000 ft.</p>