SMC Takumar 55 f radioctive?
Radioactive lenses -- group shot: (a bit drab, not a very colorful group). These lenses JAPAN Super-Multi-Coated Takumar /55 - ASAHI OPT. Co. JAPAN . Click on a date/time to view the file as it appeared at that time. Takumar is the name that Asahi Optical gave to its lenses, notably but not exclusively those for Super-Takumar lenses featured a[n improved] form of lens coating (to [reduce] 24/, 28/, 35/, 50/, 50/4 macro, 55/, 55/2, 85/ , /4 macro, /, /, /, /4, /4, /, /, / 8. 1. D Cox wrote: ThomasB wrote: carylee wrote: I have multiple Fill the gap and get a Pentax 55mm f or f2 (no thorium), I have the f2.
Radioactivity Radioactivity generally is found in three categories: The xray and gamma radiation is very penetrating, able to pierce through a foot or more of concrete, but for that reason it interacts less effectively with film or people than beta or alpha particles at closer ranges. Alpha particles can only go through a few inches of air, and are stopped by a sheet of paper. But they can interact strongly with the surface of the cornea of the eye held near the glass for long periods.
This event happens when an alpha particle emitter is used in the glass of a telescope or microscope eyepiece. Such exposures can produce cancers and radiation burns after long exposure and daily use.
Are all Takumar lenses radioactive?: Pentax SLR Talk Forum: Digital Photography Review
Beta particles can penetrate a few feet in air, or a range of thicknesses of cloth, paper, and other materials. The beta particle emitters are most important photographically.
Beta particles can penetrate camera shutters and film cassettes to fog film next to radioactively "hot" lenses left in your camera bag. Gamma and xrays can do so too, but their intensity is usually much less from the contaminants in glass than for beta particles. Not all examples of any given lens type will necessarily be radioactive. Different batches may have been made with glass from different sources. The amount of radioactive contaminants may have also varied between different lens batches too.
See our Ektar lenses pages for listing of some of the many Ektar lenses that may be "hot", based on the above observations. The "lanthar" in the Voigtlander lens name evidently originated from the Lanthanum used to create the needed high refractive index glasses needed for these lens designs.
Again, not all "Lanthar" lenses are necessarily radioactive, since the term was used for marketing on many lenses, not all of which may have used radioactive glass formulas. Lanthanum Glass in Widespread Use There are an awful lot of lenses with lanthanum glass in them. Lanthanum crown glasses were developed by Morey at the NBS in the mid 's and developed commercially by Kodak who produced several Lanthanum glasses.
They were applied to a wide variety of lenses by the 's including the Ektar series of Tessar type lenses. There are likely few lenses made in the last sixty years which do not contain some Lanthanum glass. It was one of the first high index-low dispersion glasses. Richard Knoppow, see posting of 21 Sept below. The major direct impact of radioactivity on lenses is limited to the accumulation of particle tracks in the glass especially from alpha particles.
But these changes can usually only be seen by microscopic examination. Some radiation dose monitors use such particle tracks in special glasses to monitor radiation levels in medical or military settings. However, the early glass formulas and contaminated chemicals used have produced lenses which have "yellowed" with age see posts.
This yellowing is related to on-going chemical reactions in the lens related to the chemistry of the early glass formulas used in high refractivity glasses. See our lens color pages for tips on how to test your lenses for this thorium glass yellowish coloration. Testing for Radioactivity in Lenses You can easily test a suspect lens using a sheet of high speed polaroid film see posts below. Place the lens glass element facing downward onto the polaroid sheet for a few days, and then develop.
If you see a foggy shadow or outline, you have a radioactive lens. You can also use longer exposure times with a sheet of photographic paper from your darkroom, provided you extend the exposures to several days and protect the paper from direct light fogging.
This photographic approach was how nuclear radiation was first detected by Becquerel, thanks to a fogged photographic plate placed near a sample of uranium ore. The trick still works.
You can also use a standard geiger muller counter or other instrument able to detect beta and gamma rays. Just how radioactive are typical "hot" lenses? Studies of a half dozen Leica lenses see postings below came up with 1.
This figure compares to 20 milliroentgens mrem per day maximum permissible dosage in many western countries. But that 20 mrem is for whole body exposure, while the lenses mostly emit shorter range beta and alpha particles.
On the other hand, it may take just a single gamma ray to turn one of your cells into a cancerous cell and cause a tumor. The biggest real medical danger is to users of eyepieces of radioactive glasses, where close proximity during long hours of viewing can result in high dosages to the cornea of the eye. That's a danger of another sort, but worth knowing about unless you don't mind your Leica lenses ending up classified as "low level nuclear waste".
Another professional danger is potential fogging of film due to prolonged close proximity in your camera bag between "hot" lenses and your sensitive film stocks. Finally, I was firmly put down by some Leica collectors because the official factory sources had denied that any Leica lenses were radioactive.
Are all Takumar lenses radioactive?
This stand was maintained despite a number of reports confirming that tests had shown various Leica lenses were indeed radioactive e. Turns out that the factory was well aware of these "hot" or radioactive glass lenses, but Leitz management had denied them for years see postings below and LHSA articles.
So the final casualty here is the believability of various "published" and "official" sources of information about lenses, which have denied that their lenses were radioactive to any degree. Thanks to this page and these posters and related articles and lens testing, we now know better. Chances are rather good that if you have many older lenses from the mids and before, that you have one or more radioactive glass lenses in your collection.
Related Postings I had saved this as a. In bringing it back to html the conversion has compressed out the line returns that Bob had introduced between messages.
Sorry for the readability. Mon, 16 Mar From: Eric Goldstein egoldste bu. There are no stable isotopes. The original patent for using Thorium in camera-lenses is from Before that decade, they did not have much use for it, except in certain types of gas-lamps. Currently, Thorium is considered a more practical but less energetic alternative for Uranium in nuclear power generation. The percentage of Thorium used in camera lens glass or coatings varies between 12 and 28 mass-percent.*!* PENTAX EXTRA-HOT RADIOACTIVE LENSES *!* Super-Takumar 55mm f2
It was used in this way in the 's and 's, after which companies stopped doing this since less radioactive alternatives such as lanthanium became available, making the use of radioactive material in lens-production unjustifyable any longer. It is sometimes still used in medical equipment. A list of affected lenses: Canon FL 58mm f1.
Measurements on my own copy of this lens, with the sensor directly on the front and rear glass elements highest result stated: Focusing the dosage meter different measurement on beta- and gamma-radiation yielded no stronger result than the normal background variation one can measure anywhere on Earth all the time.
Setting the dosage meter up to measure alpha-radiation in particular, which the fire department normally doesn't look for, yields about 2.