Some lenses of the 1960s, such as early Minolta Rokkor lenses, have elements to made of glass formulas which include small traces of radioactive rare-earth elements. Lenses with elements made of radioisotope-containing glass Perhaps the most famous radioactive lenses of all were the Kodak Aero-Ektars.Ĭuriously, in his notable book, A History Of The Photographic Lens, Rudolf Kingslake (head of the Eastman Kodak lens design department 1937-1968), makes only a single passing comment on the possible use of thorium in Kodak lenses.
Helios lens wiki professional#
In addition, many professional level Ektar lenses from this era contain thorium. From the 1940s through the 1960s, substantial numbers of amateur cameras were produced and sold with thoriated (containing thorium oxide) lenses, including some of the Pony, Signet, and high end Instamatic (e.g. Normally these particles are stopped by skin, but the surface of the eye can be quickly damaged by them, and at close range, the dose can be very high.īy far the most prolific known producer of radioactive lenses was Eastman Kodak. They can give a very large alpha and beta particle dose to the cornea of the eye, potentially causing cataracts and other problems. However, thoriated glass eyepieces are significantly more dangerous. Most smaller lenses with thorium elements pose a negligible risk to human health. 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.
Helios lens wiki 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. 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. 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. 5.2 Lenses Tested non-Radioactive (by contributors to this page).5.1 Lenses Tested Radioactive (by contributors to this page).4 Lenses with elements made of radioisotope-containing glass.And if you’re lucky enough to find one with a double 0, those are said to be special versions for party members only.
Helios lens wiki serial number#
Note: the first digit of the serial number will indicate the year it was made. For example, it’s easy to see lenses with the letters MC or M (multi-coated) and it’s actually better than those lenses that don’t have the marking such as Helios 44-1, 44-2, 44-3, 44-4, 44-5, 44-6, 44-7, and up. Additionally, if you find a model past 1983 or close to 1994, you can find the same lens but with a better build quality. Typically, it’s normal to find the Helios 58 mm f2 lens in the market. And best of all, those lenses are very cheap (you can find a lens from anywhere between €15-30). When both LEDs are lit, it meant that the aperture and speed have been properly set and the camera is ready to take a shot.īeing an older model with a 42 mount, the XP was relatively easier to fit with a wide variety of lenses compared to its other competitors. There was a previous model named the 12 SD and the updated XP version had a meter that had two working LEDs: one for indicating exposure and the other for underexposure.
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