Kodak Ektar Aero 2.5 radioactivity
I don't own one, nor would have a camera to match it, but I have read before here on APUG about the ultra fast Kodak Ektar Aero 2.5 lenses for aerial camera's dating back to WWII, and I know that some of you probably own one.
In recent times they seem to have gotten a bit of "cult" status due to their nice bokeh when used as portrait lens.
However, there is the question of the radioactivity of the Thorium containing lens elements, and this is the reason for this post.
In last month's edition of the Dutch photo magazine "Camera Magazine", there is an article by Stefan Heijendael, who, after seeing a intriguing advertisement for a 2.5 lens for 4x5 photography, decided to buy one.
Of course, as a good father of two kids, knowing the lens was radioactive didn't chear up himself and his family. He therefore created a do-it-yourself lead covered storage box, but of course as with all matters related to the invisible phenomenon of "radioactivity", the small nagging question kept crawling in the back of his head "Is this enough, and do I actually need to worry at all??"
So he contacted the University of Maastricht here in the Netherlands, where the medical department was willing to help.
So here it is: some real measurements of the level of radiation emitted by such a lens. Better know what you have stored in your seller! :
- At 10 cm from the back of the lens (it's the back lens element containing the Thorium additions), they measured 1.3 microsievert / hour
- At an weekly exposure of 4 hours year-round, this sums up to 270 microsievert in one year.
- The amount of Thorium was estimated to be 36kBQ.
So now the author of course wondered "Is that dangerous?" :o
Our Dutch government uses a maximum of 1000 microsievert / year as an acceptable dosage of radiation to which members of the public may be exposed. The report made up by the medical department therefore concluded that there was "No significant elevated risc", that based on moderate 4 hours weekly usage.
Now on another note, according to this link:
"Humans can absorb up to 0.25 Sv without immediate ill effects; 1 Sv may produce radiation sickness; and more than 8 Sv causes death."
Well, since 1 Sv is 1000 times the accepted year dosis of 1000 microSv, I guess death of owning a Ektar Aero is really not imminent...
Remained just one question by the author Stefan Heijendael, was his lead box completely senseless? Answer: No, 1 mm of lead reduces exposure by a factor of about 20, so if the lens is stored in such a box at more than 1 meter of a subject and with long time exposure, there are no significant riscs from having the lens around in your house...
Well, lastly, since Stefan included it as well, here's the disclaimer :
The department of radiology of the University of Maastricht, the author (Stephan) and I guess myself , do not take any responsibility for negative health effects of owning, storing and using such an Ektar Aero lens. No rights can be obtained based on the measurements. The measurements are based on just a single specimen of this type of lens, and radiation levels may vary...
Last edited by Marco B; 07-26-2008 at 12:44 PM. Click to view previous post history.
Reason: corrected 4 hours daily into what it must be 4 hours weekly exposure
Apropos to this but a bit off-topic, dye transfer paper contains Thorium as well.
Well, that's an interesting one PE, why does dye transfer paper contain Thorium? I've never handled the stuff, is it transparent and also makes use of the refractive properties of Thorium, as in the Ektar lens?
Some 60's f1.4 and faster SLR lenses used radioactive glass, f1.4 Takumars were one. A few other high speed lenses have similar glass.
We live with radiation all the time, and even going for a walk can expose you to it. My sister died from a rare cancer only seen in patients exposed to radiation fallout, she regularly walked in an area (in the UK) contaminated by fall out from Chernobyl. The farming restrictions are still in place today.
I own 3 Aero-Ektar lenses. I do not store them between my legs. HA!
Many buildings built of granite release far more radiation to the occupants. Living in high mountain regions of the world expose one to huge levels of radiation.
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Ian, what extremely sad to hear, that's the Chernobyl disaster getting way to close... and now with the short sighted renewed "push" for nuclear energy to "save" the planet, do we ever learn?
Originally Posted by Ian Grant
All of you who own Aero Ektars (and/or Apo Lanthars) and are concerned. Ship your lenses to me and I will safely dispose of them.
Originally Posted by Marco B
Everything is analog - even digital :D
The Radon gas in your basement will kill you long before any lens I know of
I definitely agree that radon is a more realistic threat to ones self and family.
I remember reading somewhere that an astronomer snapped up a surplus aero ektar for use as an eyepiece(?).. The results after several years were not good from what I recall but I wish I could find the original quote of this.
Personally me, I think i'd rather find a Graf Variable Anastigmat or a Pentac and save the weight but that's another thread.
Thorium used in dye transfer paper was there as a white colored mordant that tied the dyes in place. The Thorium cation (positive ion) formed a very insoluable salt with the anionic (negative) sulfonic acid dyes used in dye transfer. In the last instant product that Kodak was going to introduce, they used Nickel as the salt for assisting in both complexing and mordanting the dye in place. That improved dye stability as well.
So, metals, and radioactive materials have a long history in photo products.