Radioactive Lenses

Why use thorium in lenses?

Simply, thorium allowed the lens manufacturer to produce high quality lenses at a reduced price. Its optical properties of high refractivity and low dispersion allowed lens designers to minimize chromatic aberration and utilize lenses of lower curvature. Lanthanum was also used. Lanthanum has very weak radioactive properties.

Is it dangerous?

Generally NO. Estimated exposure when these lenses were in primary use was .7 mrem per year for the average photographer and 2 mrem per year for busy professionals. Normal background radiation exposure for people has been estimated at 620 mrem per year by the NRC. However, if you are concerned about the use of these lenses; don't use them.

NOTE: Thorium doped telescope eyepieces contain high levels of thorium (25%) and will cause damage to the cornea.

Lenses That May Contain Thorium or Lanthanum

Kodak Ektar 101mm f/4.5 (Miniature Crown Graphic camera) lens mfg. 1946
Kodak Ektar 38mm f/2.8 (Kodak Instamatic 814 camera) lens mfg 1968-1970
Kodak Ektanar 50mm f/2.8 (Kodak Signet 80 camera) lens mfg. 1958-1962 (3 examples)
Kodak Ektanar 90mm f/4 (Kodak Signet 80 camera) lens mfg. 1958-1962
Kodak Ektanar, 44mm f/2.8 (Kodak Signet 30, Kodak Signet 50, Kodak Automatic 35/Motormatic 35 cameras) lenses mfg. 1959-1969
Kodak Ektanon 50mm f/3.9 (Kodak Bantam RF camera) lens mfg. 1954-1957
Kodak Ektanon 46mm f/3.5 (Kodak Signet 40 camera) lens mfg. 1956-1959
Kodak Anastar 44mm f/3.5 (Kodak Pony IV camera)
Kodak Color Printing Ektar 96mm f/4.5 lens mfg. 1963
WEP Auto Weiton 35mm f2
Argus Cintagon 50mm f/2.8
Agfa Color Solinar 2.8/50
Bell & Howell Director Series (Model 1208?) XL Super 8 movie camera; Zoom Lens f: 1.2 \ F: 9-22.5 mm
Canon FL 50/1.4 (very early version)
Canon FL 50/1.8 I
Canon FL 58/1.2
Canon FD 17mm f/4
Canon FD 35mm f/2.0 (versions from the early 1970's - concave front element)
Canon FD 55mm f/1.2 S.S.C. Aspherical
Canon (SUPER-CANOMATIC LENS) R 50mm 1:1.8
Carl Zeiss Jena Pancolar 55mm f1.4
Carl Zeiss Jena Pancolar 50mm f1.8 "Zebra" (1964-67, up to serial number 8552600)
Carl Zeiss Jena Biometar 80mm f2.8 "Zebra" "(Only P6 mount version )
Carl Zeiss Jena Flektogon 50mm f4 "Zebra" "(Only P6 mount version )
Carl Zeiss Jena Prakticar 50mm f1.4 (1st version with engravings around the outer side of barrel)
Carl Zeiss Tessar 80mm f/2.8 (old silver Hasselblad version)
Enna München Lithagon 1:3.5 35mm (M42)
Focal 35mm f/2.8
Fujica Fujinon 19mm f/3.5 EBC (Arkku at mflenses.com)
Fujica Fujinon 35mm f/1.9 EBC (Arkku at mflenses.com)
Fujica Fujinon 50mm f/1.4 non-EBC early style
Fujica Fujinon 50mm f/1.4 EBC early style
Fujica Fujinon 100mm f/2.8 EBC
Fujica Fujinon 400mm f/4.5 EBC
Fujica Fujinon 600mm f/5.6 EBC
GAF Anscomatic 38mm f/2.8
Kodak Aero-Ektars
Kodak Ektanon 4-inch Projection Lens f/3.5
Kodak Instamatic M24/26 Super 8 Camera YouTube
Kodak Ektar 80mm f/2.8 (for Hasselblad 1600F and 1000F, made 1948-1950)
Kodak Ektar 135mm f/3.5 (for Hasselblad 1600F and 1000F, made 1949)
Konica Hexanon AR 50mm f1.4 (smallest aperture 16; green AE marking)
Konica Hexanon 57mm f1.2
Konica Hexanon 21mm f4
Leica 50mm f/2 Collapsible Summicron
Leitz Wetzlar Summicron 5cm f2 (M39)
Mamiya/Sekor 55mm f/1.4 (m42, chrome+black, flat rear element)
Mamiya/Sekor SX 55mm f/1.8
Minolta MC W. Rokkor-SI 1:2.5 28mm (early variants)
Minolta MC Rokkor-PG 1:1.2 58mm
Minolta MC Rokkor 1:1.7 85mm (the earliest variant of the MC line)
Mitakon (Zhongyi) 50mm f0.95 Ver I Speedmaster
Mitakon (Zhongyi) 50mm f0.95 Ver II Dark Knight
Nikkor 35mm f/1.4 (early variant)
Olympus Zuiko MC Macro 20mm f/3.5
Olympus Zuiko Auto-S 1:1,2/55 mm (first version)
Olympus Zuiko Auto-S 1:1,4/50 mm "Silvernose"
Olympus Zuiko Pen F 1:1.8/38mm
Olympus Zuiko Pen F 1:1.4/40mm
Rikenon AUTO 55mm f/1.4 (Also Sears)
Schneider Repro-Claron
Schneider 135mm f/3.5 Xenotar
SMC Pentax 50mm f/1.4
SMC Takumar 20mm f/4.5
SMC Takumar 35mm f/2.0
Super Takumar 35mm f/2.0
SMC Takumar 50mm f/1.4
Super Takumar 50mm f/1.4 (the latest version with 7 elements - red 'infrared mark' being on the left side of DoF scale '4')
SMC Macro Takumar 50mm f/4.0
Super Takumar 55mm f/1.8
Super-Multi-Coated Takumar 55mm f/1.8
SMC Takumar 55mm f/1.8 (select lenses)
Super Takumar 55mm f/2.0
SMC Takumar 55mm f/2.0
SMC Takumar 85mm f/1.8
Super Takumar 6x7 105mm f2.4
Steinheil Auto-Quinon 55mm f/1.9 KE mount
Tele-Takumar 6.3 300mm
Topcor RE GN 50/1.4
Topcon UV Topcor 50mm f/2
Yashinon-DX 28mm f/2.8 (Yashica)
Yashinon-DS 50mm f/1.4 (Yashica)
Yashinon-DS 50mm f/1.7 (Yashica)
Yashinon-DX 50mm f/1.4 (Yashica)
Yashinon-DX 50mm f/1.8 (Yashica)
Yashinon-DS-M 50mm f/1.4 (Yashica)
Yashinon-DS-M 50mm f/1.7 (Yashica)
Yashinon-DS-M 55mm f/1.2 (Yashica)
Yashinon-ML 50mm f/1.7 (Yashica)
Yashinon 55mm f1.2 (Tomioka)
Ultragon 115mm f/5.5
Vivitar Series 1 28mm f1.9
Voigtlander 50mm Nokton Prominent
Voigtlander 15cm Apo-Lanthar
Voigtlander 21cm Apo-Lanthar
Voigtlander 30cm Apo-Lanthar
Voigtlander Zoomar 36-82mm f2.8
Wollensak Raptar 28-75mm f2.3
Zenitar-M 50mm f1.7

My lens turned yellow!

If thorium doped lenses are stored for prolonged periods of time they will yellow. Regular exposure to sunlight prevents this yellowing.

If the yellowing is severe it may have an affect on the color balance of your photos.

You can de-yellow your lens. The simplest way is to leave the lens in sunlight until it clears up. This could take weeks though. A faster way is to place a UV light bulb directly over the lens. It should clear up in a few days. If you are using an incandescent bulb, be aware that it will create heat and should be placed a minimum of 6 inches from your lens. LED bulbs can be placed very close to the lens. The addition of aluminum foil, placed under the lens as a reflector may help speed up the process.