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Most smaller lenses with thorium elements pose a negligible risk to human health.
#Early nikkor lens serial numbers professional
A study carried out by the Physics department of Sweden's Royal Institute of Technology estimates that total exposure to a professional photographer using a typical thoriated lens would amount to only 0.2% yearly allowable exposure to the eye and 0.17% to the whole body under the conservative standards of the Swedish Radiation Protection Authority.
#Early nikkor lens serial numbers full
For reference, a typical chest x-ray consists of about about 10 mR, a round-trip cross country airline flight exposes a passenger to 5 mR, and a full set of dental x-rays exposes the patient to 10 mR to 40mR. (.9 m.) the radiation level is difficult to detect over typical background levels. Typical radiation levels can approach 10 mR/hr (100 μSv/h) as measured at the lens element's surface, decreasing substantially with distance at a distance of 3 ft. Warning! The mR and uSv figures stated in the paragraph below are not consistent. Nerve tissue, the grey and white matter of the Central and peripheral Nervous System, are degraded by radioactive decay products, resulting in inflammation. In addition, headache, racing heartbeat, and other stroke-like conditions are linked to upper body radiation exposure. Photographers with many hours racking focus and zoom, who experience numbness and tingling in their hands / fingers, ought seek a modern, calibrated dosimeter and carefully measure their equipment. How may a camera operator discover a hot lens w/o a geiger counter? When disassociated with their containment and labeling, these lenses pose a significant hazard to unaware salvage personnel, resellers, and particularly photographers, videographers and cinematographers. These lenses may become disposed of improperly (along with other highly radioactive sources materials and equipment) and may remain contaminated upon decommission. It is the glass itself that contains the radioactive ThO2, and the browning therein is caused by the radiation-induced formation of color centers in the glass matrix.Īttention: Second-hand market lenses originating from nuclear commercial, industrial and military applications (often coveted wide-angle objectives) may have become hazardous, neutron contaminated, radiological emitters.Įxamples may include cameras and lenses from nuclear power plants (NPP), medical radiology sources, food / packaging irradiation facilities, and atomic weapons production and research facilities. Other common misconceptions hold that it is the coatings of these lenses which are radioactive and brown over time, and that the browning occurs in the balsam between cemented elements. The presence of thorium can sometimes, depending on the mixture of other elements in the lens, cause moderate to severe browning of the lens elements. Radioactivity in lanthanum containing lenses is due to the intentional inclusion of thorium in the optical glass mix. Despite statements to the contrary, lenses containing lanthanum are not appreciably radioactive - lanthanum is only 1/10,000th as radioactive as thorium. Like fluorite, its optical properties of high refractivity and low dispersion allows lens designers to minimize chromatic aberration and use lenses of lower curvature, which are less expensive to produce. Thorium oxide has a crystalline structural similar to calcium fluoride ( fluorite). Main source of radioactivity is the use of thorium oxide (up to 30% by weight) as a component of the glass used in the lens elements. There are a significant number of lenses produced from the 1940s through the 1970s that are measurably radioactive. 5.3 Lenses Tested non-Radioactive (by contributors to this page).5.2 Lenses Tested Radioactive (elsewhere, or by contributors to this page).5.1 Lenses Tested Radioactive (by the creator of this page).4 Lenses with elements made of radioisotope-containing glass.