Radioactive lenses

I continuously update this list whenever I find more radioactive lenses that I have measured. The list can be found further down in this article.

Why are some lenses radioactive?

The radioactivity in these lenses comes from thorium oxide, and some manufacturers used as much as 30% thorium oxide by glass weight. The advantage is that it gives high refraction in thin glass and low color dispersion. In other words, you get high refraction and low dispersion. Unfortunately, the radioactivity increases with age as thorium-232 decays. Thorium itself only emits alpha particles, but during the decay process daughter products are formed that emit alpha, beta and gamma radiation. On older lenses you can sometimes see that the glass has turned slightly yellow. This does not necessarily mean that your optics are radioactive, but lenses containing thorium often become yellow-brown in the glass elements. On lenses that contain thorium and have turned yellow, you can expose the glass to UV light for a longer period of time and thereby remove most of the yellowing. You can place it in a window for a few days and the discoloration will disappear. The thorium is inside the glass itself and is not a coating or surface treatment. It was usually faster lenses that used glass elements with thorium oxide, and they therefore became radioactive. This was done to achieve better optical performance.

Even if a lens is listed here, it is not certain that your particular copy is radioactive. Lens manufacturers could change glass types within the same lens design. So the type of glass can vary by serial number, even though it is the same lens model. That is why we have started listing serial numbers for the lenses we measure ourselves.

List of radioactive lenses

Now let’s take a look at which lenses are known to be radioactive. The ones in bold are the ones we have measured ourselves in our museum:

A.Schacht Ulm Edixa-Travenar 50/2.8 rear 0.94 µSv/h, watch video >>
Argus Cintagon 50mm f/2.8
Agfa Color Solinar 2.8/50 
Agfa Karat 36 with Solinar 50mm f/2.8, front 2.41 µSv/h, watch video >>
Bell & Howell Director Series XL Super 8 with f: 1.2/9-22.5 mm
Canon FL 50/1.8, serial no. 45566, rear 3.65 µSv/h, watch video >>
Canon FL 50/1.8, serial no. 62003, rear 3.77 µSv/h, watch video >>
Canon FL 50/1.8, serial no. 127372, rear 4.19 µSv/h, watch video >>
Canon FL 50/1.8, serial no. 133942, rear 4.39 µSv/h, watch video >>
Canon FL 50/1.8, serial no. 139346, rear 4.31 µSv/h, watch video >>
Canon FL 50/1.8, serial no. 158143, rear 4.29 µSv/h, watch video >>
Canon FL 50/1.8, serial no. 206975, rear 4.45 µSv/h, watch video >>
Canon FL 50/1.8, serial no. 337589, rear 4.08 µSv/h, watch video >>
Canon FL 50/1.8, serial no. 343271, rear 3.95 µSv/h, watch video >>
Canon FL 50/1.8, serial no. 527026 is not radioactive, watch video >>
Canon FL 50/1.8, serial no. 902340 is not radioactive, watch video >>
Canon FL 50/1.4, serial no. 752101 is not radioactive, watch video >>
Canon FL 50/1.4, serial no. 847475 is not radioactive
Canon FL 50/1.4, serial no. 20153 rear 18.3 µSv/h, watch video >>
Canon FL 55/1.2 is not radioactive
Canon FL 58/1.2 rear 10 µSv/h
Canon FD 17mm f/4
Canon FD 35mm f/2.0 Serial no. 648xx measured rear 4.61 µSv/h (all with concave front lens, i.e. I, II, II and SSC I. 1971-1973 are radioactive) 
Canon FD 55mm f/1.2 S.S.C. Aspherical
Canon R 50/1.8, serial no. 49048, rear 3.87 µSv/h
Canon R 50/1.8, serial no. 55715, rear 3.46 µSv/h
Canon R 50/1.8, serial no. 56425, rear 3.82 µSv/h
Carl Zeiss Jena Pancolar 55mm f1.4 2.36 µSv/h
Carl Zeiss Jena Pancolar 50mm f1.8 "zebra" (The copy we have, not "zebra", is not radioactive)
Carl Zeiss Jena Biometar 80mm f2.8 "zebra"
Carl Zeiss Jena Flektogon 50mm f4 "zebra"
Carl Zeiss Jena Flektogon 35mm f2.8 (The copy we have is not radioactive)
Carl Zeiss Jena Prakticar 50mm f1.4
Carl Zeiss Tessar 80mm f/2.8 (older silver version for Hasselblad)
Dr Wöhler Favor Dacon 45mm f/2.8 1.38 µSv/h, watch video >>
Enna München Braun-Lithagon SLK 35mm f/3.5, rear 1.03 µSv/h, watch video >>
Focal (Kmart brand) 35mm f/2.8
Fujica Fujinon 19mm f/3.5 EBC
Fujica Fujinon 35mm f/1.9 EBC
Fujica Fujinon 50mm f/1.4 non-EBC
Fujica Fujinon 50mm f/1.4 EBC early version (The copy we have is not radioactive)
Fujica Fujinon 100mm f/2.8 EBC (The copy we have is not radioactive)
Fujica Fujinon 400mm f/4.5 EBC
Fujica Fujinon 600mm f/5.6 EBC
GAF Anscomatic 38mm f/2.8 on a GAF Anscomatic 726.
Heinz Kilfitt 40mm f/2.8 Makro-Kilar (The copy we have is not radioactive)
Heinz Kilfitt 90mm f/2.8 Makro Kilar
​Kodak Aero-Ektar
Kodak Anastar 44mm f/3.5 on Kodak Pony IV
Kodak Cine Ektanon 9mm f/1.9 on Kodak Brownie "Turret", 2.24 µSv/h, watch video >>
Kodak Color Printing Ektar 96mm f/4.5 1963
Kodak Ektanon 4-inch Projection Lens f/3.5
Kodak Ektanar 50mm f/2.8 on Kodak Signet 80 1958-1962
Kodak Ektanar 90mm f/4 on Kodak Signet 80 1958-1962
Kodak Ektanar, 44mm f/2.8 on Kodak Signet 30, 50, Automatic 35/Motormatic 35 1959-1969
Kodak Ektanon 50mm f/3.9 on Kodak Bantam RF 1954-1957
Kodak Ektanon 46mm f/3.5 on Kodak Signet 40 1956-1959
Kodak Ektar 38mm f/2.8 on Kodak Instamatic 814 1968-1970
Kodak Ektar 80mm f/2.8 for Hasselblad 1600F and 1000F 1948-1950
Kodak Ektar 101mm f/4.5 1946
Kodak Ektar 102mm f/2.8 for Graflex KE-4, front 5.63 µSv/h, watch video >>
Kodak Ektar Enlarging 127mm, front 10.6 µSv/h, watch video >>
Kodak Ektar 135mm f/3.5 for Hasselblad 1600F and 1000F 1949
Kodak Ektar 205mm f/4 for Graflex KE-4, front 35.7 µSv/h, watch video >>
Kodak Instamatic M24/26 
Kodak Retina 1B (Type 019 v2) with Schneider Kreuznach Retina-Xenar 50mm f/2.8 4.66 µSv/h, watch video >>
Kodak Retina IIc with Schneider Kreuznach Retina-Xenon C 50mm f/2.8
Konica Hexanon AR 50mm f1.4 rear 2.45 µSv/h, watch video >>
Konica Hexanon 57mm f1.2 
Konica Hexanon 21mm f4 SN 7029XXX
Konica C35 camera with 38mm f/2.8, front 2.16 µSv/h, watch video >>
Leica Summicron 50mm f/2 collapsible
Leitz Wetzlar Summicron 5cm f2 (M39)
Mamiya/Sekor 55mm f/1.4 
Mamiya/Sekor SX 55mm f/1.8 serial no. 178729, rear 1.59 µSv/h
Mamiya/Sekor SX 55mm f/1.8 serial no. 204331 was not radioactive at all, watch video >>
Mamiya/Sekor SX 55mm f/1.8 serial no. 209866, rear 4.31 µSv/h, watch video >>
Mamiya/Sekor 58mm f/1.7
Mamiya/Sekor ES 50/1.8, rear 4.72 µSv/h, watch video >>
Minolta MC W. Rokkor-SI 1:2.5 28mm early version
Minolta MC Rokkor-PG 1:1.2 58mm early version
Minolta MC Rokkor 1:1.7 85mm early version
Mitakon (Zhongyi) 50mm f0.95 Ver I Speedmaster
Mitakon (Zhongyi) 50mm f0.95 Ver II Dark Knight
Nikkor 35mm f/1.4 early model
Olympus Zuiko MC Macro 20mm f/3.5
Olympus Zuiko Auto-S 55mm f/1.2 (The copy we have is not radioactive)
Olympus Zuiko Auto-S 50mm f/1.4 with silver front, front 6.83µSV/h, watch video >>
Olympus Zuiko Auto-S 28mm tf/3.5 early model
Olympus Zuiko Pen F 38mm f/1.8, rear 7.5µSV/h
Olympus Zuiko Pen F 40mm f/1.4, rear 3.81 µSV/h, watch video >>
Olympus Zuiko Auto-S 50mm f/1.4 M42, rear 3.59 µSV/h, watch video >>
Olympus 35 ECR Zuiko 42mm f/2.8 0.81 µSv/h, watch video >>
Olympus Quickmatic Zuiko 36mm f/2.8 1.89 µSv/h, watch video >>
Pentax SMC Takumar 20mm f/4.5
Pentax SMC Takumar 35mm f/2.0
Pentax Super Takumar 35mm f/2.0
Pentax SMC Takumar 50mm f/1.4 serial no. 7065627, rear 7.59 µSv/h, watch video >>
Pentax Super-Takumar 50mm f/1.4 serial no. 3717120, rear 16.9 µSv/h, watch video >>
Pentax SMC 50mm f/1.4 PK mount, first version
Pentax SMC Macro Takumar 50mm f/4.0, rear 1.22 µSv/h, watch video >>
Pentax Super Takumar 55mm f/1.8 serial no. 2832909, rear 7.44 µSv/h, watch video >>
Pentax Super-Multi-Coated Takumar 55mm f/1.8, rear 8.71 µSv/h
Pentax Super Takumar 55mm f/2.0 serial no. 2439477, rear 8.75 µSv/h, watch video >>
Pentax SMC Takumar 55mm f/2.0 
Pentax SMC Takumar 85mm f/1.8 (85mm f/1.9 is not radioactive)
Pentax SMC Takumar 120mm f/2.8 6.34µSv/h, watch video >>
Pentax Super Takumar 6x7 105mm f2.4
Pentax Tele-Takumar 300mm f/6.3
Pentax 6x7 metered prism measured 2.31 µSv/h at the eyepiece
Porst Color Reflex MC Auto 55mm f/1.2
Ricoh Auto 126 Rikenon 35mm 2.8 0.64 µSv/h, watch video >>
Ricoh Auto Shot Rikenon 35mm 2.8 0.83 µSv/h, watch video >>
Rikenon AUTO 55mm f/1.4 (The copy we have is not radioactive)
Rodenstock XR-Heligon f/0.75 50mm 
Rolleiflex 2.8C, 1954, with Schneider Xenotar 80mm 2.8
Rollei XF A110 with Tessar 23mm f/2.8 1.95 µSv/h, watch video >>
Rollei XF 35 with Sonnar 40mm f/2.3 1.46 µSv/h, watch video >>
Schneider Kreuznach Curtagon 35/2.8 front 1.58 µSv/h, watch video >>
Schneider 135mm f/3.5 Xenotar 
Schneider Repro-Claron
Steinheil Auto-Quinon 55mm f/1.9 KE mount
Topcor RE GN 50/1.4
Topcor UV 50mm f/2
Yashica ME with Yashinon 38/2.8 front 2.63 µSv/h, watch video >>
Yashinon-DX 28mm f/2.8 0.28 µSv/h
Yashinon-DS 50mm f1.4 0.68 µSv/h
Yashinon-DS 50mm f1.7 0.76 µSv/h
Yashinon-DX 50mm f/1.4 1.35 µSv/h
Yashinon-DX 50mm f/1.8
Yashinon-DS-M 50mm f/1.4 0.57 µSv/h
Yashinon-DS-M 50mm f/1.7, rear 10.9 µSv/h, watch video >>
Yashinon-DS-M 55mm f/1.2 1.06 µSv/h
Yashinon-ML (first version) 50mm f/1.7
Yashinon 55mm f1.2 0.98 µSv/h made by Tomioka, also sold as Cosinon, Chinon, Tominon, Tomioka and Revuenon
Vivitar Series 1 28mm f/1.9 (The copy we have is not radioactive)
Voigtländer Skoparet 35/3.4, rear 2.51 µSv/h, watch video >>
Voigtlander 50mm Nokton Prominent
Voigtlander 15cm Apo-Lanthar 16 μSv/h
Voigtlander 21cm Apo-Lanthar 27 μSv/h
Voigtlander 30cm Apo-Lanthar 35 μSv/h
Voigtlander Skopagon 40/2 front 2.31 μSv/h, watch video >>
Voigtlander Super-Dynarex 135mm f/4, rear 1.49 μSv/h, watch video >>
Voigtlander Zoomar 36-82mm f/2.8 3.1 μSv/h
Voigtlander Ultragon 115mm f/5.5 1.5 μSv/h
Voigtländer VF135 with Color-Skoparex 40/2.3, front 1.34 µSv/h, watch video >>
Wollensak Raptar 28-75mm f2.3
Yashica 35 ME with 38/2.8 2.66 µSv/h measured from the front
Zeiss Super Ikonta 532/16 with Zeiss Tessar 80/2.8 9.19 µSv/h, watch video >> 
Zeiss Super Ikonta 533/16 with Zeiss Opton Tessar 80/2.8 10.06 µSv/h, watch video >>
Zenitar-M 50mm f1.7

Perspective

Normal background radiation is around 0.2 µSv/h. It may differ by a decimal or so up or down without being abnormal, and there may also be some variation in the precision of the meter being used. From here on in this section we are talking about µSv and not µSv/h, meaning the total dose and not dose per hour. To give some perspective, if you sleep next to another human being, you receive 0.05 µSv. Yes, we are all slightly radioactive. If you eat a banana, you receive 0.1 µSv. Bananas contain potassium-40, which is radioactive. One of the beneficial minerals that bananas are rich in is potassium, which naturally consists of 0.01% of the radioactive isotope 40K (potassium-40). No, it is not dangerous to eat bananas. However, if you eat 1000 bananas at once, the radioactivity could become high, but I think other problems would occur before that. That means 1000 bananas at the same time, not spread out over a lifetime, so you can safely eat bananas. If you X-ray your arm, you receive 1 µSv, a dental X-ray gives 5 µSv, and if you fly from New York to Los Angeles you receive 40 µSv.

The lenses emit gamma radiation

Alpha particles are large and heavy and consist of helium nuclei with two protons and two neutrons. Because of this, they quickly lose their kinetic energy, reach a maximum of about 10cm in air, and can be stopped by something as simple as a sheet of paper. They cannot penetrate skin, but they are very dangerous if you eat or inhale them. Beta particles consist of electrons and/or positrons. Since they are smaller, the ionization is lower and they can therefore penetrate further into matter. They can travel around 10 meters in air, but only penetrate a millimeter or so into skin. The radiation is easily stopped by something like a plastic sheet. Beta radiation can leave shadows on analog film. Gamma radiation, according to science, consists of photons and is electromagnetic radiation. Gamma radiation travels at the speed of light and passes easily through most metals, though not lead. What we measure here is gamma radiation.

Are there any new lenses that are radioactive?

No, this only applies to old lenses and cameras. Today, lanthanum is used instead.

Radioactive viewfinders

Now I come to a bigger problem: some manufacturers also used thorium oxide in viewfinder glass. In that case, you have a radioactive source right next to your eye, and it is not protected by skin either. Some cameras that may have radioactive viewfinders include the Pentax 6x7 and Pentacon Six. I have measured 2.31 µSv/h from the viewfinder on a Pentax metered prism. If someone asked whether they could shoot gamma rays into your eye, you would probably say no to that question, regardless of the level of radiation. Even though this is relatively weak radiation, it is still 10 times higher than background radiation. I would not use such a viewfinder myself.

Are radioactive lenses dangerous?

The levels of radioactivity are very low, but you should not grind down the glass and eat it, or inhale it. That would be bad. You should also not sleep with the lens under your pillow. As a rule, the radiation is so weak on the lenses I have measured that already at a distance of 10 cm from the optics, no radiation can be measured at all.

Are Russian lenses radioactive?

Many people believe that Russian lenses might be the most radioactive lenses of all. This is probably due to the Soviet Union’s often inadequate handling of radioactivity and its regrettable attitude toward human life. Despite this, Russian lenses are usually not radioactive at all. The Helios-44 series, which are the best-known Russian lenses, are not radioactive at all. The only Russian lens I know of that actually is radioactive is the Zenitar-M 50mm f/1.7, and even then only certain versions of that lens contain thorium oxide in the glass. So not all Zenitar-M 50mm f/1.7 lenses are radioactive.

The decay chain

For those who are truly interested, you can see the decay chain here:

Th-232  ──α──▶  Ra-228  ──β──▶  Ac-228  ──β + γ──▶  Th-228
              ↓
              (gamma-weak)

Th-228  ──α──▶  Ra-224  ──α──▶  Rn-220  ──α──▶  Po-216
                                        ↓
                                        (short-lived, gas)

Po-216  ──α──▶  Pb-212  ──β + γ──▶  Bi-212
                           │
                           ├──α──▶  Tl-208  ──β + **γ** (2.6 MeV) ─▶  Pb-208 (stable)
                           └──β + γ──▶  Po-212  ──α──▶  Pb-208 (stable)
 

Is it really gamma radiation?

Yes. Watch the video below to see that it really is gamma radiation we are dealing with. The radioactivity can vary between different lenses even when they are the same model, usually depending on when they were manufactured.

 

 

Can you set fire to a wad of paper using a radioactive lens? Watch the video below.

 

I created a YouTube channel to save videos from measurements all in one place. Click here to watch >>

Text and image: © Thomas Lövgren

Updated 2026-05-26