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Kodak Printing Ektar
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PostPosted: Tue Oct 01, 2019 1:15 pm    Post subject: Re: Kodak Printing Ektar Reply with quote
kds315* wrote:


Agreed, never have I heard about rdiation issues with lenses containing Lanthanum glass!

https://www.fourmilab.ch/documents/radiation/lens/


Thanks for the link. Would be nice if ANY site had correct information though. For sure the radiation from Thoriated lenses is not all Alpha. Most may be, but the Kodak lenses I own are putting out significant Beta radiation that can't be stopped by putting in a metal box, let alone by the sheet of paper or few cm of air claimed by most of the online references.


PostPosted: Tue Oct 01, 2019 2:59 pm    Post subject: Re: Kodak Printing Ektar Reply with quote
Ray Parkhurst wrote:
Ernst Dinkla wrote:
macheck wrote:
Does anybody have any experience with Kodak Printing Ektars ?
I have two of them 4.5/113 and 4.5/103, what type of outer thread they have ?
http://camerapedia.wikia.com/wiki/Kodak_lenses, informs they are of Heliar type, photofinishing, 5-element lenses.

Macheck


No experience with them ....

Given their manufacturing period, the Heliar design, the radioactive Lanthanum or Thorium (first more likely) element(s) in them and their (L) coating, they could be compared with the Voigtländer Apo Lanthar wide format lenses that still fetch high prices on Ebay. Not the modern 65/125/180mm Apo Lanthars produced more recently by Cosina but the older wide format ones in leaf shutters.

Main differences; barrel design without adjustable aperture and an optical design aimed at printer magnifications. It still would be interesting to see whether the parts could fit in the older leaf shutters to give them an adjustable aperture. Speculative of course ....

I have not seen that many portraits and landscape images made with them, mainly close ups of flowers etc, either because the users expect them to perform better at those distances or they really are not suited for portraits etc.


From my understanding, Lanthanum is not generally radioactive. There is an isotope of Lanthanum which is radioactive, but it is extremely rare. According to my readings, radiation in lenses is almost exclusively due to Thorium. I don't have info on the ratio of Lanthanum and Thorium used in various glasses, but I'd assume the "Lanthar" lenses would use mostly or exclusively Lanthanum rather than Thorium. Are the Lanthar lenses radioactive? If so, it's probably due to some amount of Thorium added to the mix.


Well I went by the low measurement result in this thread and yes the Lanthanum could have some amount of Thorium added. The vintage Voigtländer Apo Lanthars are radioactive as well due to that addition. https://www.arnecroell.com/voigtlaender.pdf page 13

Addition: Voigtländer Apo Lanthar 15cm as measured by Croell has 16 uSv/h which should translate to 1.6mR/hr . That is about twice the measured RA of 1mR/hr of the Printing Ektar mentioned in this thread. Measuring method, instrument, kind of radiation assumed equal, probably is not though.


PostPosted: Tue Oct 01, 2019 5:29 pm    Post subject: Reply with quote
If it's radioactive, then almost for sure there is Thorium in the mix.

I was not able to get the measurement window right up against the lens surface, so my reading was a bit lower than it would be if I were closer.


PostPosted: Tue Oct 01, 2019 7:31 pm    Post subject: Reply with quote
Ray Parkhurst wrote:
If it's radioactive, then almost for sure there is Thorium in the mix.

I was not able to get the measurement window right up against the lens surface, so my reading was a bit lower than it would be if I were closer.


Well the Lanthanum used was possibly not that pure either. There is an interesting article/thread here that is more specific on Kodak lenses with RA and describing the sources of Lanthanum and Thorium. Certain monazite sands found in India. https://www.bnphoto.org/bnphoto/LostSites_MonaghanRadioactive.htm There is also mention of the use of Lanthanum in more lenses in that period than we know, simply because it was one of the first high-index low-dispersion glasses available. Kodak was ahead in the development of Lanthanum glasses, 7 types, before even Schott had it in the catalog.


PostPosted: Wed Oct 02, 2019 12:57 am    Post subject: Reply with quote
Ernst Dinkla wrote:
Ray Parkhurst wrote:
If it's radioactive, then almost for sure there is Thorium in the mix.

I was not able to get the measurement window right up against the lens surface, so my reading was a bit lower than it would be if I were closer.


Well the Lanthanum used was possibly not that pure either. There is an interesting article/thread here that is more specific on Kodak lenses with RA and describing the sources of Lanthanum and Thorium. Certain monazite sands found in India. https://www.bnphoto.org/bnphoto/LostSites_MonaghanRadioactive.htm There is also mention of the use of Lanthanum in more lenses in that period than we know, simply because it was one of the first high-index low-dispersion glasses available. Kodak was ahead in the development of Lanthanum glasses, 7 types, before even Schott had it in the catalog.


Looking a little deeper, I found the Thorium decay chain:

Thorium-232 (1.41e10 years)-->Alpha
Radium-228 (5.7 years)-->Beta
Actinium-228 (6.1 hours)-->Beta
Thorium-228 (1.9 years)-->Alpha
Radium-224 (3.6 days)-->Alpha
Radon-220 (55 seconds)-->Alpha
Polonium-216 (0.14 seconds)-->Alpha
Lead-212 (10.6 hours)-->Beta
Bismuth-212 (61 minutes)-->Beta to Polonium-212 (3e-7 seconds)-->Alpha to Lead-208 (Stable)
OR
Bismuth-212 (61 minutes)-->Alpha to Thallium-208 (3.1 minutes)-->Beta to Lead-208 (Stable)

99.98% of the Thorium on the planet is Thorium-232, mainly because it has such a long half-life, while the other isotopes have relatively short half-lives. The general consensus is that Thorium generates Alpha particles, but what actually happens is that each Thorium-232 atom produces (eventually) a Radium-228 atom. That Radium-228 degrades relatively quickly through the decay chain above, generating 3 or 4 Beta particles and 4 or 5 Alpha particles, until it terminates at Lead-208 (!!!).

It is these Beta particles that I have been reading on my monitor.

99.91% of the Lanthanum on the planet is Lanthanum-139, which is stable. 0.09% of Lanthanum is Lanthanum-138, which generates either a Beta particle to become Cerium-138, or a Gamma ray to become Barium-138. I don't know the decay chain for these, but I think that the 0.09% prevalence of Lanthanum-138, with its half-life of 1e11 years (10x that of Thorium-232) is why folks say that Lanthanum is 10000 times less radioactive than Thorium.
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