Is my lens RADIOACTIVE ?

[krisalid_tasho]

<p>Hi, <br>

I read about thorium treatement of lenses and I was wondering if the lens of my PORST CR-7 (FUJICA previously) 50mm f1:1.2<br>

This one: <a href="http://www.kamera-geschichte.de/files/porst_slr_reflex_cr7_d.htm">http://www.kamera-geschichte.de/files/porst_slr_reflex_cr7_d.htm</a><br>

Year of production seems 1981. Does anybody know if there has been a radioactive treatement to this lens? </p>

[krisalid_tasho]

<p>here is the lens <a href="

[JDMvW]

<p>Here's an older post here about "glow-in-the-dark" radioactive lenses (<a href="../medium-format-photography-forum/009X3q">link</a> ).</p>

<p>Consensus seems to be that there's not enough radioactivity to be much of a threat.</p>

[ken_jeanette1]

<p>Just don't lick the front element, and you'll be OK</p>

[dweezil]

<p>The radioactivity of these lenses ( that have thorium in them) is supposed to be less than the normal background radiation.<br>

see <a href="http://cameras.alfredklomp.com/fed5/radiation/">this </a> for a test result.</p>

[Rob_the_waste]

<p>I've used a thorium based lens (Industar 61LD) many times in the past few years. The eyesight in my third eye actually seems to be improving.</p>

[george_shihanian]

Some lenses have the radioactive element in front, some in the rear. It's harmless as long as you regularly don't hold it up to your eye and use it as a telescope.

[john_shriver]

<p>I have a Victoreen CD V-700 Geiger counter, and I assure you that there are lenses that are a lot more than twice the backgroun radiation. My very early collapsible Summicron 50/2 gets it excited, as does my RE GN Topcor 50/1.4. Both are also yellow-brown when you look through them, the radiation has turned the glass brown -- a known problem.<br>

I have an Industar 51-L/D, and it doesn't get the Geiger counter going.</p>

<p> </p>

[marc_rochkind]

It's best to put some serious metal between lenses such as these and your face. I'm thinking Contarex or Leicaflex class. No flyweight, porous, Olympus OMs or Pentax K's.

 

--Marc

[awahlster]

<p>It's not the glass that has been ambered but the Balsum glue used to hold groups together. The Canon 35mm f2.0 with the concave front element is one of the best known of the thorium glass lenses. As are a number of Kodak made Aerial photography lens made during WWII.<br>

It's not a safety concern as long as you don't carry the thing in your front pocket for a few years.<br>

I have one it is the most awesom sharp and contrasty B&W lens I have ever handled.</p>

 

[t_nu_tamm]

<p>Rob, I-61LD contains lanthanum, not thorium. According to Wikipedia, each Toyota Prius contains 10-15 kg of it, too.</p>

[konrad_beck1]

<p>Krisalid:<br>

If your lens was build after around 1978/79, it is very unlikely that it contains radioactive elements as the major optical glass manufacturers stopped their production by that time. A 50/1.2 lens is also of the more "modern" design: most fast standard lenses with radioactive elements were 55mm or 58mm f/1.2, though some 50/1.4s of the early 1970's like the Olympus Zuiko also contained radioactive elements.</p>

[astral]

<p><em>"The radioactivity of these lenses ( that have thorium in them) is supposed to be less than the normal background radiation."</em> That is quite wrong. The emissions from almost all thoriated lenses is many times average 'background' radiation. In the case of the 35/2 SMC Takumar and Canon FD for example, levels are between 13 and 20 times 'background' at the rear of the lenses, according to my measurements. Typically such lenses have the thoriated glass in the rear elements rather than in the objective. It should be noted that such levels do not present a health risk <em>in normal use</em> ; there is plenty of factual information on this issue on the web, including 'official' sources. <br /> <br /> In any case, the Fujinon EBC 50mm f1.2 is definately <em>not </em> thoriated (if it is, then my meter is very <em>seriously </em> defective!) and there is no convincing reason to believe that the Porst is any different.</p>

[Richard Williams]

<p>'Typically such lenses have the thoriated glass in the rear elements rather than in the objective.'</p>

<p>Is there a potential risk of eventual film fogging with some designs? I've seen it claimed that the early Leitz Summicron had a flint glass rear element with enough lead in it to protect the film from the thoriated front element. I don't know how plausible this is.</p>

[astral]

<p>"<em>Is there a potential risk of eventual film fogging with some designs?</em> " (Richard )</p>

<p>Very unlikely -I've discussed this issue several times with professionals in what used to be the UK National Radiological Protection Board (now renamed), together with the health question. I understand that if a film is used at a 'normal rate', and not left in a camera for long periods (implying weeks), adverse effects will not normally be seen. Metal shutters offer a little more protection to the film than cloth ones, and high ISO film may show effects sooner than slower emulsions as is the case with security X-Rays. On balance the advice <em>to me</em> was (paraphrase) "<em>don't worry about i</em> t".</p>

<p>In relation to health issues, the advice was that in "normal use" there will be few significant effects, though everything is 'measurable'. So, in terms of handling thoriated lenses, as long as they are not carried around hour after hour, day after day close to the body, the <em>total body</em> <em>exposure </em> is quite small - roughly in the same order as a flying the Atlantic a couple of times. The difference is that thoriated lenses don't affect the whole body, just the area they are close to: so place and length of exposure are important. Hence the advice <em>to me</em> was (paraphrase): "<em>if you are not using it don't wear it around your neck all day long</em> ".</p>

<p>I base <em>my </em> working practice on the advice I have been given, which is broadly in-line with my own direct experience of handling exotic natural rocks and minerals. The difference is that <em>some </em> rocks are a <em>lot </em> 'hotter' than these thoriated lenses, but (of course) they are not normally handled for protracted periods. Also, some granite areas and those affected by radon gas may pose a significantly higher "24-7-365" radiation health risk than 'wearing' a thoriated lens for many hours each day.</p>

<p>To sum up, all I can say it that I am 'comfortable' using commonplace <em>mass production</em> 'radioactive' lenses (the specialist Aero Ektars are a different issue). Other folk may be less comfortable, and that is understandable. Some folks may wish to follow-up with their own information gathering - these three websites may help as a start:</p>

 

<ul>

<li><a rel="nofollow" href="http://www.hps.org/publicinformation/ate/q1356.html" target="_blank">http://www.hps.org/publicinformation/ate/q1356.html</a> </li>

<li> <a rel="nofollow" href="http://www.orau.org/ptp/collection/consumer%20products/cameralens.htm" target="_blank">http://www.orau.org/ptp/collection/consumer%20products/cameralens.htm</a> </li>

<li><a rel="nofollow" href="http://www.orau.org/ptp/collection/consumer%20products/consumer.htm" target="_blank">http://www.orau.org/ptp/collection/consumer%20products/consumer.htm</a> </li>

</ul>

<p>I believe that the last link puts the issue into perspective.</p>

[krisalid_tasho]

<p>Thank you guys. Now I have an idea about it!</p>