Radio-active Pentax lenses!

I was getting some info from 'the web' now I have the wonderful COMPUTER about Kodak Aero-Ektar lens 178mm f 2.5 and typed in 'Kodak Aero-Ektar Lens' into 'Google'and pages came up with some disturbing discussions about radio-active emissions from Ektars including some 'early Pentax Takumars'such as 55mm f1.8 and 1.4 and 6x7 Pentax Takumars. I own such lenses as well as the Aero-Ektar,which I have tried on my 6x7 with extension tubes to help to focus. I have had it in the house since the 1960s,it is in a cupboard in my darkroom now about 5 feet away from where I work processing and enlarging. The Takumars are in my boy's bedroom in another cupboard. Does any member have any thoughts about possible effects;I don't have access to a Geiger Counter but some of the Americans on the Ektar pages have had their lenses checked and will only keep them in a basement away from their children.[/i]

Wow, that's a question! I can only speak personally, but I don't feel worried by it, I doubt that much radiation is coming from a Takumar lens....

Watches with hands that fluoresce are also guilty of being radioactive, or at least at one time they were.

You will also get a pretty healthy dose of radiation when you fly away on holiday.

Hi,
The lenses you are refering to used an element with thoriated glass. It generally only affected the Super Multi Coated versions and some of the SMC ones. The glass was used to cut down on dispersion and distortion. Thoriated glass has a very high refractive index which means a thinner lens element. One side effect is that these lenses can gain a strong yellow caste over time. The good news is that this can be cured by exposing them to UV light, even sunlight will cure them.

I wouldn't worry about the level of radioactivity. The levels are extremly low. I remember at school a couple of physics experiments needed a radioactive source. This was kept in a lead lined box, handled with special tongs and gloves by the teacher with all the kids well back due to the rules. At the end of the experiment the teacher would "point" the source at the geiger meter and it would click away at an increased rate. He would then replace the source and put his watch near the geiger counter which would then buzz away at about 10 time the rate! I can dig out several papers which quantify the effect of these lenses if you wish. They all suggest that normal camera lenses are not a problem. The glass was also used in the eyepieces of some TV/movie cameras. The advice is that very prolonged use of these with the lens very close to the eye could have some effect over a long period. As far as still camera lenses go, you don't spent hours with them very close to your eye. Yes they may provide an incresed count on a Geiger but many other everyday things will produce far more. What's more, I haven't heard of a case of any film fogging caused by them and therefore they are unlikely to record much on the detectors that many have to wear in certain jobs. Personally, I am far more worried about the long term use of mobile phones. Many thousands of these lenses were produced and I have yet to hear of a litigation case despite the culture these days.

More info here http://www.orau.org/ptp/collection/consumer%20products/cameralens.htm and here http://hps.org/publicinformation/ate/q1356.html (I don't think I will be using my "radioactive" Taks for several million hours )

Regards
Kim

What a MINE of information on the Pentax User forums!! Many thanks to KIM for the info and web links,I had a look and put my mind at rest.