[rhodopsin]

Save your thoriated lenses for later!

8 grams of thorium could replace gasoline in cars | Geek.com

U.S. Researcher Preparing Prototype Cars Powered by Heavy-Metal Thorium

[RioRico]

A very wise move. Pentax lenses in general are hazardous. After only 36 years of exposure to them, my hair has turned gray and started to fall out.

This is especially noticeable (and hazardous) if you grind-up the lenses and eat them. And they're dangerous from a distance too, and retroactively. Why, my hair started turning silver 30 years ago, and I didn't even get my first SuperTak until 2008!

Yes, SuperTaks are extremely dangerous. If you encounter any, wrap them in lead foil and ship them to me -- I'll dispose of them safely, I promise.

[Blue]

I will do that. I need to dispose off about 7 Taks. Wait for my PM (sitting..., so you will not get tired of waiting )

I am glad you suggested sitting.

[Pepe Guitarra]

That explains many things I am going through, and I have had it only for few weeks. Instead, I had the 8 elements STak that does not have the Thorioum (sp?) coating.

A very wise move. Pentax lenses in general are hazardous. After only 36 years of exposure to them, my hair has turned gray and started to fall out.

John

[stevebrot]

not have the Thorioum (sp?) coating

The thorium is not a coating, but is actually part of the formula for the glass.


Steve

[Nesster]

The effects of thorium radiation were studied extensively in the early '60s, and found to cause hypnotic suggestibility in the test subjects. Pentax devised an ingenious method of leveraging this - if you play the sound of the Spotmatic shutter backwards, you'll hear "Buy More Pentax"

[callagh11]

So, correct me if I misunderstand (I may have bitten by Birsbane spider and become, er, stupider) eating 1.4 taks is not only cheaper than eating banana's it's better for my health.
Damn, and I had plans to use it to focus light onto some Tri-X.

Matt
(in Brisbane where banana prices are comming down, but still rival S-M-C taks pound for pound...)

[RioRico]

So, correct me if I misunderstand (I may have bitten by Birsbane spider and become, er, stupider) eating 1.4 taks is not only cheaper than eating banana's it's better for my health.

Correct. And unlike bananas, Taks won't go extinct within the next decade, according to biologists. So you can enjoy Tak smoothies without contributing to global decay. Huzzah!

[Frogfish]

Well if they were produced in the last year ... very radioactive.

[Mgarber]

I have a 6x7 format 105mm f2.4 which is showing moderate yellow tint. How do I get rid of it?

I heard that UV light will rid the lens of this tint, so I bought a 50 watt reptile light that emits UVA (and heat, unfortunately) and I've had it positioned just above the lens for 3 days, but it's had no effect (as far as I can tell from waking up in the morning and looking at it.)

The lens' serial number is 4241097. I heard the serials aren't sequential, so that might be pointless. But my other concern is that the lens might actually have some kind of slightly yellow coating, but every website I've checked says it's Thorium.

How do I fix my Thorium affliction?

[vladimiroltean]

I have a 6x7 format 105mm f2.4 which is showing moderate yellow tint. How do I get rid of it?

I heard that UV light will rid the lens of this tint, so I bought a 50 watt reptile light that emits UVA (and heat, unfortunately) and I've had it positioned just above the lens for 3 days, but it's had no effect (as far as I can tell from waking up in the morning and looking at it.)

The lens' serial number is 4241097. I heard the serials aren't sequential, so that might be pointless. But my other concern is that the lens might actually have some kind of slightly yellow coating, but every website I've checked says it's Thorium.

How do I fix my Thorium affliction?

Sell it.

[womble]

Having just acquired a Super Tak 35/2 I now have a very yellow lens. Unfortunately, we're unlikely to see the sun for the next four or five months... I'll just have to stick with loading the camera with Tri-X

K.

[TomB_tx]

My Super Takumar 50 f1.4 lenses "un-yellowed" amazingly in a day using an 18" fluorescent black-light fixture I've had stashed since the 1960s. Possibly the bulb you have doesn't cover the same UV wavelengths. I put a layer of aluminum foil in the front cap and placed the lenses front-down in a plastic tub, with the light fixture across the tub so it was about 2" over the back side of the lenses; then put a "tent" of aluminum foil over the fluorescent tube to concentrate the light down on the lenses, but with enough gap around the foil so any heat could escape. The lenses never felt warm with this setup, so no worry about the lubricants migrating inside the lenses.
The SuperTaks do have an amber lens coating instead of the bluish tint of the later SMC lenses, but the coating doesn't cause yellow tint in pictures.
My lenses gave a yellow cast visible in the viewfinder as well as on film. I left the lenses under the light for a couple days, even though the change over the first night was amazing. That got rid of the yellow tint.

[Mgarber]

My Super Takumar 50 f1.4 lenses "un-yellowed" amazingly in a day using an 18" fluorescent black-light fixture I've had stashed since the 1960s.

Was it the same kind of black light that one would find in a night club or fun house? I have some friends that run bars, they might have one like that.

[TomB_tx]

Was it the same kind of black light that one would find in a night club or fun house? I have some friends that run bars, they might have one like that.

Yes it was - same type.