Radioactive Lenses and Every part About Them

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There’s a whole lot of misinformation about radioactive lenses – from scare tales about rising an additional arm and getting most cancers, all the way in which to saying that radioactive lenses are completely innocent. The reality is someplace between the 2 extremes and requires cautious consideration. In any case, these lenses comprise radioactive substances, and we must always deal with them with some care.

Such as you, I wished to be secure and perceive tips on how to cope with the radioactive lenses. I had so many questions: Find out how to deal with them? What injury might they do to me or the digicam? Or possibly, I ought to give them away to an individual from the discussion board providing to “take them away from me” to save lots of me from hurt? (Good strive, buddy!)

After studying numerous articles, research, and books, I’ve compiled the solutions to the commonest questions.

Well being Physics Poster from Oak Ridge Nationwide Laboratory (1947)

Disclaimer: This text is only informational, and shouldn’t on no account be used as medical, well being, radiation safety, or security recommendation, implied or not.

What Makes Classic Lenses Radioactive?

Thorium and lanthanum, primarily. Digicam lenses comprise optical glass made with numerous uncommon components like lead, boron, calcium, lanthanum, and thorium dioxide. These components have distinct optical properties, permitting producers to create lenses of superior high quality.

Each lanthanum and thorium dioxide are radioactive, though radioactivity from lanthanum is so small that it’s not detectable with out delicate lab tools. Lanthanum is simply weakly radioactive as a result of solely 0.089% of it’s lanthanum-138, a radioactive isotope and the remaining 99.9% is non-radioactive lanthanum-139.

Unique components reminiscent of Thorium, Lanthanum and Zirconium are added to glass mixtures to create the excessive refractive indexes mandatory in subtle lens designs. Choice of premium portions of glass from the big glass pots, stringent spectrophotometric checks after stress and pressure checks present the precious uncooked glass for final use in lens components. —Konica Hexanon Lens Information, Konica Digicam Firm, 1972

Historical past of Radioactive Lenses

In 1945, Paul F. De Paolis, from Eastman Kodak Firm, filed a United States Patent 2,466,392 for Optical Glass, which launched thorium and optical glass making properties.

This software pertains to glass having optical values in a variety that’s helpful for the designing of optical devices. Particularly, this software pertains to such glass having an index of refraction for the D line (n) within the vary between 1.65 and 1.68 and an Abbe worth (v) between 52.5 and 57.0.

Typically, the glasses herein described are non-silicate and embody because the glassifier boric oxide in an quantity between 35 and 40 % by weight; lanthanum and thorium oxides in considerably equal quantities, larger than ten %, of every; and barium oxide and both calcium or magnesium oxide. —United States Patent 2,466,392.

Kodak produced a few of the first radioactive lenses for aerial surveillance – the Aero-Ektar. Different producers like Canon, Konica, Asahi Pentax, and others additionally used thorium of their lenses made between about 1945 and 1980.

Producers largely used thoriated glass for the quickest, dearer lenses, such because the f/1.2s and f/1.4s, however slower radioactive lenses additionally exist.

Finally, by the early Eighties, the thoriated glass fell out of use for client lenses – as a result of manufacturing facility staff’ well being considerations and client radiophobia following nuclear accidents. Newer formulations appeared, providing related properties with out the added threat of radioactivity.

Optical Properties of Thoriated Lenses

The addition of thorium oxide, or thoria, to the glass will increase the refractive index whereas sustaining low dispersion. These properties are particularly useful for making optical glass.

A excessive index of refraction means gentle travels slower inside the glass, and subsequently, modifications its course extra simply. Lenses can have a decrease profile, require much less materials and thus be lighter.

Low dispersion, outlined by Abbe quantity, permits lenses to appropriate chromatic aberration, guaranteeing the identical focus is maintained all through the entire vary of colours within the seen spectrum, creating sharper photos.

Combining these properties permits for lenses with wonderful optical efficiency.

What’s Thorium?

Thorium is a weakly radioactive metallic chemical component with the image Th and atomic quantity 90. All recognized thorium isotopes are unstable. Probably the most secure isotope, 232Th, has a half-life of 14.05 billion years, or in regards to the age of the universe. It decays very slowly by way of alpha decay, beginning a decay chain named the thorium collection that ends at secure 208Pb. —Wikipedia

Thorium is a naturally occurring, most ample radioactive component within the earth’s crust. Thorium is comparatively secure and has a half-life of 14 billion years.

Do Radioactive Lenses Emit Solely Alpha Particles?

Not likely. Whereas it’s true that pure thorium decays by emitting an alpha particle as acknowledged above, that is solely the beginning of the lengthy collection of decays that emit alpha, beta, and gamma radiation till it ends with the secure isotope of lead. You possibly can learn it as such:

Thorium 232 -> releases alpha α -> turns into Radium 228, then
Radium 228 -> releases beta β- -> turns into Actinium 228, and so forth.

Picture by BatesIsBack / Wikimedia Commons and licensed below CC BY-SA 3.0.

The above decay chain demonstrates that thoriated lenses comprise thorium and its daughter components: radium, actinium, radon, polonium, bismuth, thallium, and lead in minute portions, ensuing from gradual thorium decay.

What Is Bremsstrahlung Radiation?

When beta particles decelerate inside denser supplies, such because the barrel surrounding the lens, they create electromagnetic radiation by releasing a photon – an x-ray or gamma-ray. This secondary radiation known as “bremsstrahlung, German for “braking radiation”.

Most classic lens barrels are metal, copper, or aluminum and produce tiny quantities of secondary gamma radiation. The heavier the shielding materials, the extra bremsstrahlung radiation is emitted.

As a result of how little beta decay there may be, the ensuing bremsstrahlung radiation can also be minimal. Nonetheless, it’s price mentioning for completeness to know what sorts of radiation you would anticipate from a lens.

Risks of Radioactive Lenses

Glass mud and fantastic particles

Components within the thorium decay chain are extremely poisonous and harmful on their very own and in bigger portions. Nevertheless, the quantities current within the lenses are tiny and solely exist for a short while.

Breaking the lens won’t “launch” the radiation or the poisonous components which stay within the glass lattice construction. Nonetheless, it is going to contaminate the premises and make it simpler to ingest or inhale small bits of radioactive mud.

Alpha particles can solely penetrate a number of micrometers of the outer layers of human pores and skin and are innocent – so long as they’re exterior the physique.

Alpha-emitting particles are considerably extra harmful contained in the physique. Ionizing properties of the alpha particles trigger injury when they’re near the cells — particularly, these within the respiratory tract and lungs and the digestive tract, abdomen, and intestines.

Guarantee you don’t smash, grind, scratch, or scrape the lens components to keep away from getting radioactive particles contained in the physique. As a superb measure, I additionally wash my palms after dealing with them.

Well being Physics Poster from Oak Ridge Nationwide Laboratory (1947)

Eye injury from radioactive lenses

For makes use of of thoriated optical glass which are approved below this exemption, the lens could be enclosed by different supplies or there could be extra materials between the lens and the tissues of an uncovered particular person, and solely photon exposures could be of concern. Nevertheless, in unauthorized makes use of of thoriated optical glass, reminiscent of eyepieces of optical devices, publicity to the attention to alpha and beta particles additionally could be of concern. This concern is due to the proximity of the glass to the attention and lack of ample absorbing materials between the supply and tissues of the attention. —nrc.gov NUREG-1717 Web page 3–288

Elevated radiation publicity can trigger cataracts within the eyes, subsequently keep away from needlessly exposing your eyes – put on glasses and don’t put radioactive lenses near the bare eye when cleansing or dealing with them.

Robert C. McMillan & Steven A. Horne – Eye publicity from a thoriated optical glass – irpa.internet

Testing confirmed that straightforward eyeglasses successfully defend radiation emitted from the lens – solely one-tenth of the radiation will get by way of. I measured roughly 3006 CPM by way of glasses versus roughly 28000 CPM on the floor.

Again of a Konica Hexanon AR 57mm f/1.2 displaying 27847 CPM of radiation on the floor
A radioactive lens with easy glasses
Measurement exhibits a big drop of radiation when glasses are positioned between the lens and the counter

Radiation publicity from radioactive lenses

Based on the analysis (under), radioactive lenses are comparatively secure. We’re commonly uncovered to radiation from numerous sources every single day, which mixed give a extra vital dose than using radioactive lenses would:

  • Strolling round exterior within the solar (fundamental contribution to the annual radiation dose)
  • Staying at residence (Radon from the constructing supplies, tiles)
  • Consuming bananas (Accommodates potassium-40)
  • Consuming brazil nuts (Accommodates Radium-226)
  • Flying on an aeroplane (about 2μSv/h of Cosmic radiation)
  • Getting an x-ray on the physician
  • Sleeping subsequent to somebody (the opposite individual is radioactive to us (potassium-40)
  • Having a smoke detector (incorporates americium-241)
  • Having a granite countertop (uranium and decay merchandise)
  • Smoking (releases radium, lead-210, polonium-210)

The overall gamma power launched each second from the Carl Zeiss Tessar, however, was nearly 32 MeV/s. The contribution from this for a photographer to the utmost annual dose to the entire physique was calculated to be simply 0.17 ‰. That is corresponding to the elevated dose from beta radiation. Thereby the beta and gamma radiation from the Carl Zeiss Tessar are equally non-hazardous. These ratios are so near zero that the conclusion drawn on this thesis is that there are not any radiation-related well being hazards concerned within the utilization of any of the digicam lenses measured. —An Evaluation of Residual Radiation in Thoriated Digicam Lenses. Jonathan Wäng and Viktor Henningsson, 2013.

Find out how to Establish Radioactive Lenses?

Probably the most dependable technique to decide whether or not the lens is radioactive is by measuring it with a Geiger counter. Nevertheless, few folks have easy accessibility to 1, and in that case, a visible inspection may very well be used as a backup.

Visible inspection can reveal hints that the lens is radioactive – radiation over time causes yellowing of the lens components. Nevertheless, ageing, in addition to the composition of the glass, can even trigger discoloration of the glass.

Trying by way of the lens at a white sheet of paper reveals the weather’ yellowing in comparison with the encompassing white paper. A major distinction in tone signifies the next probability that the lens is radioactive. However, clear glass doesn’t imply that the lens doesn’t comprise radioactive supplies – it may well go each methods. Radioactive lenses lose their yellow tint when uncovered to UV gentle.

Utilizing a white background to see the yellowing of the lens. Hexanon AR 57mm f/1.2 is radioactive, whereas the Hexanon AR 35mm f2 just isn’t radioactive. It’s evident that the AR 35mm is whiter.
Canon FL 58mm f/1.2 clearly displaying off its yellow components

Is Lens Coating Radioactive?

Lens coatings are available in quite a lot of colours, which can seem yellow when considered from an angle. The coating shade just isn’t associated to lens radioactivity and might be of any shade for radioactive, and non-radioactive lenses.

Some sources incorrectly state that the lens coatings are radioactive – that’s not the case. The precise glass incorporates thorium – not the coatings. For instance, Mamiya makes use of yellowish coatings on most of their classic lenses, whereas solely a few of these lenses are radioactive.

Why Do Radioactive Lenses Yellow Over Time?

Radiation creates F-centers within the glass as a result of radioactive decay displaces electrons, which trigger the glass to take a yellow or brown tint.

UV gentle can clear a few of the yellowing. It might take as much as 7 days of publicity to the solar, or UV gentle sources to reduce the yellowing. Nevertheless, I like the nice and cozy shade solid in my images, and go away the lenses as they’re – it’s a distinctive “characteristic” of a thoriated lens.

Find out how to Retailer Radioactive Lenses?

To keep away from elevated radiation publicity – retailer the radioactive lenses as far-off from your self as fairly attainable. When you’ve got a selection, don’t preserve them within the bed room or areas the place they’re near people for extended intervals. Though the exposures are small, all of them add up over time.

I measured a drop of radiation readings to background ranges at about 1-1.5 meters away from the lenses.

An aluminum case is an effective possibility as a result of it’s a good shielding materials for alphas and betas. However, storage container materials doesn’t make as a lot of a distinction within the dose charges as distance, so if you’re frightened – enhance the gap between your self and the lenses.

At a distance of about 45 cm from three radioactive lenses pointing at detector I get 236 CPM
Identical distance, however with lens caps or UV filters on the extent drops to 86 CPM – about twice the background degree.

Measurement Tools

I measure my lenses utilizing GQ GMC 600+ and GQ GMC 300E+ Geiger-Muller counters. GQ GMC 300E+ makes use of a extra widespread M4011 GM tube, which isn’t very delicate to Alpha radiation however detects Beta and Gamma. In the meantime, the GMC 600+ makes use of LND 7317 pancake GM tube and may be very delicate to all sorts of radiation.

Do Radioactive Lenses Injury Cameras?

All electronics are prone to radiation injury to a point – digital cameras undergo from the formation of sizzling pixels on the sensor.

A easy take a look at exhibits how radiation would possibly have an effect on the digicam sensor. After 90 seconds of publicity with a lens cap, a radioactive lens left seen “excited pixels” within the picture. That’s the place the high-intensity particles hit the sensor. The pixels returned to regular for the following body, and weren’t “caught”, however I feel it’s a good suggestion to take away radioactive lenses from the digicam physique and be on the secure facet.

Extra details about sizzling pixels might be discovered on Hubble telescope digicam, CMOS picture sensors, and Reddit.

Posting Radioactive Lenses

Radioactive lenses don’t normally trigger issues for posting. I had numerous lenses shipped with none bother, besides from one time, when a Mamiya Sekor 55mm f/1.4 was being shipped from the USA utilizing the eBay International Transport program. International Transport despatched the lens again to the vendor with a be aware stating that radioactive supplies are usually not permitted.

Parcel rejected when sending a Mamiya Sekor 55mm f/1.4

Are Radioactive Lenses Nonetheless Being Made?

Present client lenses don’t comprise thorium – it has been changed with newer formulations of glass, avoiding the radioactivity downside. The primary concern was the manufacturing facility staff’ well being – no person would wish to polish and grind the glass and expose themselves to radiation. Additionally, folks’s worry of radiation makes the completed product difficult to promote.

Curiously, thorium remains to be utilized by the USA navy, within the state-of-the-art International Hawk drones.

On June 21, 2017, a U.S. Air Drive RQ-4 International Hawk crashed close to Mt. Whitney, which lies on the boundary between Sequoia Nationwide Park and the Inyo Nationwide Forest in California. It’s rugged, closely forested terrain, and now the service needs somebody to go in there and recuperate components of the drone.”

“Thorium is a radioactive materials and decays by way of alpha emission. If the lens has been burned or it has been melted the potential for alpha radiation publicity is increased. —TheDrive

The plane additionally has an optical lens which is impregnated with Thorium to reinforce optical properties (just like many business optics) —The contract doc

If the USA navy chooses to make use of thorium to energy their drone optics, maybe we are able to say that it’s nonetheless one of the best glass when absolute high quality is required?

Are Radioactive Lenses Higher?

A few of the most wonderful classic lenses ever made are radioactive. Is thorium to “blame” for his or her success, or is that this solely a coincidence? Tough to say, however the truth that thoriated lenses are utilized in top-quality optical techniques of navy drones suggests the previous.

I examined fairly a number of radioactive lenses and fell in love with them. The Mamiya 58mm f/1.7 exhibits distinctive optical efficiency – photos are sharp and contrasty with placing heat color.

I’m but to seek out an optically poor instance of a radioactive lens – fairly the opposite – they’re all wonderful.

Trendy non-radioactive lenses surpass these classic lenses in absolute sharpness and distinction. Moreover, they normally characteristic extra advanced designs, with extra components and teams. Nevertheless, the optical properties of the classic lenses are extra pleasing to some folks – together with me.


Concerning the creator: Mantas Kalausis is the photographer behind the web site Lens Legend, a web site about classic and trendy lenses with every thing from pattern images to opinions. The opinions expressed on this article are solely these of the creator. You will discover extra of Kalausis’ work on his web site, Fb, Twitter, and Instagram. This text was additionally revealed right here.



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