File:Radioactive Lenses (group shot).jpg

English: Radioactive lenses -- group shot:

(a bit drab, not a very colorful group)

These lenses exhibit low-level radioactivity, probably caused by Thorium Oxide added to the glass to enhance its optical properties.

Top Row (Left to Right):

- CANON LENS FL 58mm 1:1.2 - CANON LENS FD 35mm 1:2 (chrome filter ring) - CANON LENS FD 55mm 1:1.2 S.S.C. ASPHERICAL - CANON LENS FD 17mm 1:4 S.S.C. - CANON LENS FL 50mm 1:1.8

Middle Row (Left to Right):

- AUTO YASHINON-DX 1:1.4 f=50mm YASHICA - AUTO YASHINON-DS 50mm 1:1.7 YASHICA - ASAHI OPT. Co. JAPAN Super-Multi-Coated Takumar 1:2/35 - ASAHI OPT. Co. JAPAN Super-Multi-Coated Takumar 1:1.8/55 - ASAHI OPT. Co. JAPAN Super-Multi-Coated Takumar 1:1.4/50

Bottom Row (Left to Right):

- Ernst Leitz GmbH Wetzlar Summicron f=5cm 1:2 (collapsible, M39) - OLYMPUS OM-SYSTEM G.ZUIKO AUTO-S 1:1.4 f=50mm (early) - FUJINON 1:1.4/50 FUIJI PHOTO FILM CO. (metal focus ring) - UV TOPCOR 1:2 f=50mm TOKYO KOGAKU - RE GN TOPCOR M 1:1.4 f=50mm TOKYO KOGAKU

Taken with Canon T2i (550D) with Canon EF 20mm f/2.8 lens. ISO 100, f/8, 0.3 sec

During the shot, the level of gamma radiation measured at the camera (about 0.5 meter above the lenses) was about 4-5x normal background, as measured with a Ludlum 44-2 NaI scintillation probe. One meter away, the level dropped to about 2x normal. (Ludlum 2221 settings: HV=775V, threshold(LLD)=10mV, background about 1900 CPM).

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Measurements (informal, unscientific)

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. . -------------------------------------------------------------------- 1) Surface (near contact) readings with geiger counter . . --------------------------------------------------------------------

These are the typical readings where the Geiger Mueller tube is pressed up as close to the front or rear glass as possible.

Ludlum Model 2221 Scaler/ratemeter, with Ludlum 44-9 Pancake GM probe Settings: High Voltage = 900 V, Threshold (LLD) = 55 mV

The 4 readings on each row are "F=r1/r2 R=r3/r4 CPM [x%]"

- r1 = close to front
- r2 = close to front with plastic cap (little/no alpha, some beta, most gamma)
- r3 = close to rear
- r4 = close to rear with plastic cap (little/no alpha, some beta, most gamma)  
- x% = Max(r1,r3)-background / same value for Pentax 50/1.4 S-M-C Takumar 

Lens caps off, focus at infinity, aperture fully open (may not affect some lenses) Each reading was a 10 minute average. Plastic cap off - background level was about 28CPM (26-30) - from 2x10 min averages. Plastic cap on - background level was about 27CPM (25-29) - from 4x10 min averages.

Lens: F=r1/r2 R=r3/r4 CPM Readings

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Slightly radioactive lenses: (not in group shot -- low radioactivity) - - - - - - - - - - - - - - - - - - -

Nikon Micro-Nikkor AI-S 200mm f/4: (not in group shot -- too tall, would be fuzzy) F=92/53 R=28/29 CPM [0.2%]

Canon FL 28mm f/3.5: F=34/34 R=102/65 CPM [0.3%]

Canon EF 135mm f/2 L: F=167/74 R=28/32 CPM [0.5%]

Canon EF 200mm f/2.8 L: F=170/69 R=27/26 CPM [0.5%]

Canon EF 400mm f/5.6 L: F=170/72 R=29/27 CPM [0.5%]

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Radioactive lenses (presumably with thorium): - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

Olympus Zuiko MC Macro 20mm f/3.5: (not in group shot -- too small, no lenscap) F=818/342 R=37/33 CPM [3%]

Canon FD 35mm f/2 (concave): F=524/473 R=1422/1061 CPM [5%]

Topcon UV Topcor 50mm f/2: F=212/190 R=1427/933 CPM [5%]

Yashica Auto Yashinon-DX 50mm f/1.4: F=54/47 R=2715/1157 CPM [10%]

Canon FL 58mm f/1.2: F=481/449 R=3074/2321 CPM [11%]

Yashica Auto Yashinon-DS 50mm f/1.7: F=525/466 R=3434/2474 CPM [13%]

Topcon RE GN Topcor 50mm f/1.4: F=623/591 R=4483/3278 CPM [17%]

Steinheil Auto-Quinon 55mm f/1.9 KE mount (chrome, black arm): F=6542/2661 R=184/165 CPM [24%]

Canon Lens FD 17mm f/4: F=126/96 R=8957/3635 CPM [33%]

Olympus G.Zuiko 50mm f/1.4: F=12238/5397 R=201/191 CPM [46%]

Canon FL 50mm f/1.8: F=95/85 R=14116/5346 CPM [53%] {Super Canomatic R 50mm f/1.8 is about the same}

Pentax S-M-C Takumar 55mm f/1.8: F=194/169 R=17251/7028 CPM [64%]

Leica Collapsible Summicron 50mm f/2 (M39): F=17769/7597 R=863/668 CPM [66%]

Pentax S-M-C Takumar 35mm f/2 (49mm filter): F=738/641 R=18663/8336 CPM [70%]

Auto Rikenon 55mm f/1.4: F=132/129 R=22937/7565 CPM [85%]

AUTO mamiya/sekor 55mm f/1.4 (M42, chrome+black, flat rear glass) F=2500/2008 R=26078/8430 CPM [97%]

Pentax S-M-C Takumar 50mm f/1.4: F=858/778 R=26838/12512 CPM [100%]

Canon FD 55mm f/1.2 S.S.C. Aspherical: F=33251/16713 R=6226/4725 CPM [124%]

Fujica Fujinon 50mm f/1.4 (old style): F=26115/13222 R=35197/16306 CPM [131%]

Konica Hexanon AR EE 57mm f/1.2 (green EE): F=40328/17606 R=28597/10412 CPM [150%] . . .

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2) Gamma counts 100mm away from side of lens . . ---------------------------------------------------------------

These readings should give a better indication of how much exposure you'd get farther away from the lens.

Ludlum Model 2221 Scaler/Ratemeter, with Ludlum 44-10 "high energy" gamma scintillation probe (2" x 2" NaI)

Settings: High Voltage = 850 V (middle of 500–1200 V range), Threshold (discriminator) = 10 mV. These settings gave a background reading of about 4400 CPM, which is near the minimum that this probe is supposed to read for the background. I wonder if the NaI crystal is degraded?

Method: The probe was placed horizontally on a table, with a small amount of lead shielding near the crystal. This reduced the background reading to about 1500cpm. The lens being measured was placed with the "hotter" end (front or back) downward, at the same level as the bottom of the probe. The lens was wide open (if possible), focused at infinity (if possible), and had both front and rear caps on (correct caps, when available). A 10 minute run with the 2221 scaler was done, and compared to 10 minute runs with no lens (background).

In the table, the "xxx CPM", value is xxx = (C-B)/10, where C is the 10-minute count 100mm away from the lens, and B is the 10-minute (shielded) background count. The "[ppp%] is the xxx value for this lens compared to the xxx value for the 50mm f/1.4 S-M-C Takumar, computed as a percent.

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Lens: xxx CPM [ppp%]

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Olympus Zuiko MC Macro 20mm f/3.5: 132 CPM [0.5%]

Yashica Auto Yashinon-DX 50mm f/1.4: 1043 CPM [4%]

Canon Super-Canomatic R 50mm f/1.8: 2292 CPM [9%]

Canon FL 50mm f/1.8: 2393 CPM [10%]

Canon Lens FD 17mm f/4: 3129 CPM [13%]

Steinheil Auto-Quinon 55mm f/1.9 KE mount (chrome, black arm): 3774 CPM [15%]

Topcon UV Topcor 50mm f/2: 4146 CPM [17%]

Pentax S-M-C Takumar 55mm f/1.8: 4790 CPM [20%]

Olympus G.Zuiko 50mm f/1.4: 5042 CPM [21%]

Auto Rikenon 55mm f/1.4: 5750 CPM [24%]

Leica Collapsible Summicron 50mm f/2 (M39): 7576 CPM [31%]

Minolta MC W.Rokkor - SI 28mm f/2.5: 11241 CPM [46%]

Yashica Auto Yashinon-DS 50mm f/1.7: 12018 CPM [49%]

Canon FD 35mm f/2 (concave): 14463 CPM [59%]

Topcon RE GN Topcor 50mm f/1.4: 19108 CPM [78%]

Canon FL 58mm f/1.2: 19290 CPM [79%]

Canon Super-Canomatic R 58mm f/1.2: 19328 CPM [79%]

Pentax S-M-C Takumar 35mm f/2 (49mm filter): 20087 CPM [82%]

AUTO mamiya/sekor 55mm f/1.4 (M42, chrome+black, flat rear glass) 21251 CPM [87%]

Pentax S-M-C Takumar 50mm f/1.4: 24350 CPM [100%]

Konica Hexanon AR EE 57mm f/1.2 (green EE): 30656 CPM [126%]

Fujica Fujinon 50mm f/1.4 (old style): 36486 CPM [150%]

Canon FD 55mm f/1.2 S.S.C. Aspherical: 46532 CPM [191%]

Note: There is no detectable gamma radiation coming out from four of the lenses marked "slightly radioactive" in the first section, so they do not appear in this section.