[ZombieArmy]

My exact lens:
Fuji Photo Film Co. (Fujinon) 55mm f/1.8 Lens Reviews - Miscellaneous Lenses - Pentax Lens Review Database

I'm just curious, I know not all yellowed lenses are radioactive. If I had a geiger counter I'd check for myself.

[Driline]

Just keep it away from your nads man if you ever want to have kids.

[ZombieArmy]

Just keep it away from your nads man if you ever want to have kids.

But would it help me develop super powers?

[boriscleto]

But would it help me develop super powers?

Only if it bites you.

[ZombieArmy]

Only if it bites you.

What if I point it at my Tarantula and then have her bite me.

Of course the point is moot of the lens isn't radioactive

[pathdoc]

Are you asking if it's a threat, or are you asking because you want to submit a pic to the radioactive lens club?

[WPRESTO]

Camerapadia has a long list of lenses that have been positively tested for radioactivity because of thorium oxide in some lens elements (go to Camerapedia or GOOGLE "radioactive camera lenses" then click on Camerapedia among the search results). The Fujinon f1.8 is not on the list, but the f1.4 is. It's been well known to Pentaxians that some of the early 50mm f1.4 M42 Super Takumar lenses are radioactive*, together with several other early Pentax lenses especially the extreme specification WA models (20mm f4.5; 35mm f2). The old standard test: in complete darkness place the lens, caps off and filter threads down, atop a small sheet of printing/enlarging paper. Leave for perhaps 48 hours, then develop the paper. If the lens is radioactive, a dark circle will appear where the lens was sitting. No need for Stop and Fix trays unless you want to send a black spot to someone, .

*I still have mine on my 1st version Spotmatic, but it has nothing to do with the ghosts, gargoyles, demons, and other monsters I can only see with my right eye.

[ZombieArmy]

Are you asking if it's a threat, or are you asking because you want to submit a pic to the radioactive lens club?

Pure curiosity, also the latter would be nice but it seems like none of the fujinon 55 f1.8s are radioactive. Funny, wonder what causes the yellowing then.

[pathdoc]

I recently bought Ansel Adams' books "The Camera" and "The Negative". In the latter, he talks about a technique called "prefogging", that is, give the film a little tiny bit of exposure under controlled conditions, then expose the desired image for better shadow detail. It made me wonder - mostly half-seriously only - whether leaving one frame of a 35mm film for a prolonged period behind the shutter of a camera with one of these lenses in it (especially in the days when shutters were all cloth) might have created this effect and helped "lift" some images, thus leading to the reputation some of those lenses enjoy.

Then again, this hypothesis could easily be disproved either by getting the same results digitally or shooting through a fresh roll of film really fast.

[stevebrot]

Funny, wonder what causes the yellowing then.

Is the lens visibly yellowed or just "warm" in its rendering? A lens yellowed by radiation has a distinctive appearance, sort of a dim brownish tint, that is quite obvious.

You may find this discussion on the Flickr "M42 Fujinon" group pertinent:

https://www.flickr.com/groups/1170632@N20/discuss/72157622940516503/


Steve

[Not a Number]

The Canadian Balsam used for cementing elements can yellow with age.

And not all radioactive lenses will yellow either. It seems the yellowing is caused by chemical changes in impurities in the thorium salts and later lenses lack these impurities.

[ZombieArmy]

Is the lens visibly yellowed or just "warm" in its rendering? A lens yellowed by radiation has a distinctive appearance, sort of a dim brownish tint, that is quite obvious.

You may find this discussion on the Flickr "M42 Fujinon" group pertinent:

Radioactive thorium Lenses | M42 Fujinon lenses | Flickr


Steve

Lens is nearly amber when looking at the color of the lens itself.

[stevebrot]

The Canadian Balsam used for cementing elements can yellow with age.

And not all radioactive lenses will yellow either. It seems the yellowing is caused by chemical changes in impurities in the thorium salts and later lenses lack these impurities.

Yes, the balsam cement may yellow with age and it is also true that radiation may not result in yellowing. Here are a few points:

• Yellowing or other color changes in irradiated glass is a well-known phenomenon caused by chemical-structural changes to the the glass (displacement of electrons resulting in so-called color centers). Whether a glass will yellow when irradiated depends on its composition.
• Some lenses are radioactive due to intentional doping, usually with thorium (all isotopes are radioactive). Most radioactive lenses fall into this category.
• A small number of lenses have incidental radioactivity secondary to poor purity of ingredients added to the melt
• While color changes may result from doping glass with radioisotopes, the same may be accomplished with direct exposure to strong radiation
• The various "cures" for yellowing (heat, UV light, visible light, etc.) all depend on "bumping" of electrons back to ground state to disrupt the color centers
• I have heard a couple of explanations as to why thoriated glass disappeared from camera optics in the early-to-mid 1970s:
  • Improved designs and manufacturing process made thorium doping unnecessary and its use was dropped to cut costs and simplify manufacturing
  • Regulations were tightened regarding thorium in consumer goods
  • Inhalation health risk to workers from thorium dust
  Of the above, I lean towards the first explanation.

It may be noted that some lanthanum-doped lenses (e.g. Industar 61 L variants) are measurably radioactive, though probably not from the weakly radioactive lanthanum. It is thought that thorium was also added to the mix as part of the "secret sauce".


Steve

[stevebrot]

Lens is nearly amber when looking at the color of the lens itself.

When looking "at" the lens or "through" the glass?


Steve

[ZombieArmy]

When looking "at" the lens or "through" the glass?


Steve

It's definitely very colored when looking at it. Looking through it it's hard to tell and I can't mount it because of the stupid metal tab on the thing that I need to file down.