Kodak Ektar 101mm - Thoriated?

EASmithV · Oct 21, 2011

Hey,

I was looking at a list of lenses, and the 101 Ektar was on it. I couldn't tell if it was tested for radioactivity by the author, or was found to be radioactive by the author. Does anyone know if the 101mm Ektar was Thoriated?

Bob-D659 · Oct 21, 2011

It won't hurt you if it is, well, unless you grind the the glass up and eat it.

EASmithV · Oct 21, 2011

I'm not worried about safety, this is in the interest of curiosity

Dan Fromm · Oct 21, 2011

I've had a number of lenses known to have been made with thoriated glass. Three TTH process lenses, one Repro-Claron. All had elements that were deep yellow or brownish before treatment with UV-B light.

I have two 101/4.5 Ektars, both older than the lenses mentioned above. All of their elements are crystal clear. No thoriated glass there, sorry. Whose list says they have it?

2F/2F · Oct 21, 2011

Hi,

Thorium lenses are harmless, but the glass yellows, making them unsuitable for most color shooting. You can get the yellow out via UV exposure, or just leave it in and shoot black and white only.

hpulley · Oct 21, 2011

I have an old thorium lens, wonderfully sharp and up to about a yellow #8 Wratten filter by now. I've heard that UV/sunlight can bleach it out but I like the effect for B&W.

guitstik · Oct 21, 2011

The early Minolta SR pre- MC lenses are supposed to be coated with thorium but I have yet to run across one. A friend of mine has a pre-AI Nikkor lens that has turned yellow from the thorium but that is the only one I have ever seen. I have been wanting to find an SR mount lens that has turned but no luck so far, I have even gone to the point of buying lenses off eBay from sellers with poor feedback to no avail.

brucemuir · Oct 21, 2011

I have a 35 1.4 Nikkor from the thorium period.
It's quite yellow.
I may try to clear it up because it's almost a full stop slower now.

I used to have a few 101 Ektars but they were all the Luminized versions and I have never heard these ever had thorium.

The honking fast Aero Ektars do.

MarkS · Oct 29, 2011

The 101 Ektars are perfectly normal Tessar-formula lenses- they have no thorium glass. Generally lens makers used thorium-containing glass for special high-performance optics (AeroEktars, 35/1.4 lenses, etc.) where the greater refractive index of thorium glass was needed to achieve the desired image quality. The state of the art has improved since those days, and thorium glass is no longer necessary (and there are probably regulations against its use).

AgX · Oct 29, 2011

I'm puzzled languagewise:

shouldn't it be "thoriumated" (if at all)?

Kodak Ektar 101mm - Thoriated?

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