Steve Cushing Impresionist Fine Art Photography

Embracing imperfection, recording emotions, one impression at a time…

Radioactive Lenses

The universe, began as part of a fireworks display on August 20, called the Big Bang, 13.8 billion years ago. To the sincere delight of series fans, the series has been running ever since, continuously, during prime time. There was no matter, only energy in the form of radiation flowing almost evenly everywhere. It took some time for protons and other elementary particles to form from the quarks, and the young universe had to cool down enough to form the first atoms from these elementary particles: the first atom in the periodic table was born from the marriage of a proton and an electron. : hydrogen .

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I am writing first about the radioactivity that can be found in our environment because many people only know about the phenomenon from the media's response to nuclear energy, nuclear weapons and related accidents, which is why they see some kind of diabolical power and ancient enemy in it.

If you think that no one today would use radiation to kill, remember that not so long ago the Russian secret service used such methods.

Alexander Litvinenko was a lieutenant colonel in the Russian State Security Service (FSB), then fled to Britain and lived there for years. On 23 November 2006, most likely at the behest of his former employer, a radioactive isotope of polonium-210 (mixed with the tea he had consumed) was injected into his body during an assassination attempt, effectively destroying him to death. His body radiated so strongly that, according to the coroner who dissected him, "it was the most dangerous coroner's inspection ever.”

So the lenses must also be dangerous….. not quite.

Nothing could be further from this ...The radioactive elements such as thorium can make sharper images formed by the lens, and without them there could be no life on Earth . Things are multiple, but simple: the constant decay of radioactive elements inside the Earth, such as uranium and thorium, produces heat, which helps keep the planet's interior, including the outer core, warm. The outer core is made up of liquid metals in which convective eddy currents work continuously, maintaining the Earth’s magnetic field as a huge dynamo (with varying intensities, but now for billions).

This magnetic field forms the magnetosphere, which protects us from the life-destroying particle currents of the solar wind and cosmic radiation. If you admire the magnificent northern light, it is the remainder of the rays that have managed to seep into the atmosphere at the northern or southern ends of the magnetosphere ( virtually circulating to the corners due to Lorentz force , where they condense and react brightly).

Without radioactive decay, there could be no life on this planet in the form it is known today. Mars, for example, because it is much smaller than the Earth (and therefore its nucleus is smaller) has cooled much earlier, and its magnetosphere is absent due to the lack of molten nuclei, so the solar wind has long swept away much of its atmosphere and turned it into the realm of eternal frost.

So what about radioactive lenses. As you’ve probably heard, in the history of photography, manufacturers have used thorium (and other radioactive elements) in countless cases to make their optics. Mainly because thorium in optical glasses significantly reduces scattering indices and improves refraction , thereby actively reducing chromatic aberration. In thorium oxide-containing lens systems, the surface curvature of each member may be less, making them less expensive to manufacture.

In addition to thorium, which is named after Thor, lanthanum often occurs, but its radioactivity is a fraction of that of thorium. Most of these materials were used by Eastman Kodak in the 1940s, 50s, and 60s. Today Asahi Takumarok lenses are the most famous radioactive optics.
Thorium was originally sourced by producers from India, where it is found in large quantities in monazite sand. Monazite is a mineral that is naturally reddish brown in colour and contains a wide variety of rare earth metals . Lanthanum also occurs in a significant proportion (~ 20%) in the same substance.

Although it would be logical to know the half-life that the radioactivity of radioactive optics decreases over time, the reality is different: the decay of thorium can also produce radioactive materials that have a stronger total radiation than the original thorium. Thus, over a period of time, radioactivity may even increase in the affected lenses . The decay product of thorium is radium , which is radioactive in itself. The latter has previously been widely used in medical procedures in radiotherapy (the radioactive gas produced by the decay of radium, radon, has been captured and used in inhalation therapy), but as it is very rare, it is now caused by other radiation sources.

Radium was discovered only 20 years before Marie Curie , and at the time people were not aware of its health risks. However, because it glowed beautifully in the dark, it was ideal for making watch dials. At that time small amounts of toxic radium were especially good for health, which, along with three times the average salary, led many people wanting to paint watch dials. However, the damage was irreversible, and the onset of tooth loss could even be followed by jaw detachment, bone fractures, and other severe organ problems. Because those affected usually died from radiation exposure to their bodies within a year, the cancer did not have time to develop.

Your lens on the shelf is going through a lot of changes over time - in terms of its material. The effect of changing the thorium-radium ratio on image quality could be the subject of separate research, but knowing the half-lives, none of us will wait for this alive.

But your lenses are totally safe. In the long run, the radioactive components may turn the glass yellow or, in more severe cases, brown . This can be corrected to some extent by the white balance of the digital frames, so you can take photos without any problems with, for example, the highly yellow Takumar. Yellowing can be cleaned to some extent with UV light. A continuous UV cure for a few days can already visibly reduce yellowing. You can then use the UV light source to shoot paint that shines beautifully with its light.

Not all yellowing is due to radioactivity . In many cases, the Canadian balm for attaching glued lens elements to each other turns yellow, which is completely harmless.

Today, thorium oxide is replaced by less radioactive lanthanum oxide in the optical industry.

According to the online literature, the strongest measured radiation is typically around 100 μSv / h on the lens surface, but it drops drastically even over short distances. For Takumarok, the strongest measured value was around 20 μSv / h.

I know, after all, everyone is wondering how strong this radiation is and how much to fear it. In parallel, the maximum value is around 20 μSv / h:

  • a banana (rich in potassium , which also has a radioactive isotope) means a radiation dose of 0.1 μSv / h
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The average background radiation that can be measured continuously on the Earth's surface is between 0.1 and 0.2 μSv / h (cheap detectors also set themselves to this basic value), but in some places where there is more natural radioactive material in the soil, up to 10 μSv / h. h can also be; this may come from the following sources


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  • natural or artificial radioactive particles in the atmosphere
  • cosmic background radiation
  • radioactive materials from geological deposits on Earth
  • planned or accidental radioactive contamination of human origin (production and use of nuclear fuels, nuclear weapons experiments, power plant accidents, medical sources, etc.)
the most radioactively contaminated areas of the Earth:
  • 0.3 μSv / h can be measured in Hiroshima (still a prosperous city)
  • 1.64 μSv / h measured in Jáchymov (Czech Republic), the world's first uranium mine
  • Marie Curie , one of the pioneering researchers in radioactivity in the laboratory to date 1.5 μSv / ha handle and radiation from the back of the chair (these were captured many times after working with radioactive elements)
  • Radiation intensity at 0.8 μSv / ha in New Mexico, Trinity test site, where the first experimental nuclear blast was conducted
  • whatever the surprise, an average flight of 0.5 μSv / h at an altitude of 5,500 meters, 1 μSv / h at 7,200 meters, 2.2-3 μSv / ha at 10,000 meters (the thinner atmosphere above our heads provides less protection against cosmic background radiation )
  • In Chernobyl around 5 mSv / h 100 meters from the exploded reactor (this is a dose of a dental X-ray),
  • In Fukushima , an average of 10 μSv / h can be measured at the power plant accident site
  • In the ghost town of Pripyat , in some places not far from the Chernobyl accident, the intensity of radiation can be as high as 500 μSv / h
  • although not many of us will be astronauts, astronauts will suffer radiation doses of up to 80,000 μSv / h in addition to the Earth's protective atmosphere
  • however, smokers receive the most radiation: they directly expose their lungs to an annual dose of 160,000 μSv / h with cigarette smoke (due to the radioactive pollonium and lead it contains).

After that, you can roughly understand the average "takumar radiation" of 20 μSv / h is extremely low. According to the online literature, radioactive lenses are not dangerous at all due to the shielding effect of the machine frame. Viewers and viewfinders containing thorium oxide lens elements alone can be problematic because we bring our eyes very close to them, which is not protected by the epithelial layer (the epithelial layer effectively absorbs alpha radiation). However, this is not the case in the world of digital machines at all. In light of this, you may be sleeping a little better and you won’t be afraid of being attacked at night by a radioactive monster on the greenery coming out of the lens on the shelf or worse your ears.

Doctors say the less than 100 μSv / h radiation does not cause any direct damage to organs . However, it is true that in the long run, ionizing radiation can increase the risk of cancer because the body is only able to correct DNA defects due to the altered behavior of ionized particles to some degree. This self-healing mechanism is the reason why some people can survive even a lethal radiation dose for decades.

If, for some reason, you also receive a higher dose of radiation than you are allowed to develop and your radiation sickness develops, your symptoms will initially be weakness, loss of appetite, nausea and vomiting, which can be alleviated for a while - deceptively. After that, however, fever, diarrhea, bleeding, vomiting, hair loss, and painful open wounds begin to form. There is a cure even from this phase, but certain complications (such as swelling of the brain and therefore edema) can lead to death.



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