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Some quick Super Takumar 50mm f/1.4 questions.
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PostPosted: Wed May 11, 2022 4:55 pm    Post subject: Some quick Super Takumar 50mm f/1.4 questions. Reply with quote
Hello.
I have recently found an offer to purchase a 7 element, 6 blade Super Takumar 50mm f/1.4 for around 75€. There's two things I need to know.
1. Is it usable on a Canon EOS 6D mk. I? It shouldn't protrude too far since it doesn't have 8 elements.
2. There is a tiny ding on the front element, the seller said he can physically feel it so it's not fungus like I worried. Is there any chance that this damage to the glass could end up leaking radioactive dust? Perhaps this is a paranoid question but I want to be sure.


PostPosted: Wed May 11, 2022 6:10 pm    Post subject: Reply with quote
No the radioactive element is one of the internal ones and you'd need to grind up that specific element and ingest it before you would potentially have an issue of any radiation entering your body. There are reports of the takumar 50mm 1.4 lenses interfering with the mirror on the 6d so I would avoid it unless your willing to have a bit of the mirror shaved off the camera.

You can use Nikkor and Olympus lenses without an issue on that body but personally I'd opt for a mirrorless Sony system but that does restrict your AF lens choices.

$75 for a damaged 50mm F1.4 is a bit much tbh


PostPosted: Wed May 11, 2022 6:58 pm    Post subject: Reply with quote
Canon 5D mirror hits rear element of 7-element 1:1.4 / 50mm M42 TAKUMARs sometimes, but only when lens is focused to (or past) infinity. Turning focus ring slightly releases mirror without visible damage to mine over several years use with dozens of hits. Mine seemed to be temperature sensitive -- mirror did not hit in warm weather; hit more often when cold, sometimes only in portrait mode but not landscape, very intermittent.

The mirror hits 1:2 and 1:3.5 / 35mm TAKUMARS sometimes.

Forget the 1:3.5 / 24mm -- camera reports ERR99 and must be powered off and lens removed.

The mirror hits 1:4.5 / 20mm sometimes.

The FISHEYE, MACRO-TAKUMARs, and focal lengths greater than 50mm work fine -- no mirror hit.

Here's hoping that little front element "ding" is actually something that will easily clean off with a little solvent., such as water or lens cleaning fluid.


PostPosted: Wed May 11, 2022 8:47 pm    Post subject: Reply with quote
If you’re planning to use many mf lenses in the future, I would definitely opt for a mirrorless fullframe camera. I think the Sony A7 is the cheapest option.


PostPosted: Wed May 11, 2022 10:08 pm    Post subject: Reply with quote
Layer-cake wrote:
No the radioactive element is one of the internal ones and you'd need to grind up that specific element and ingest it before you would potentially have an issue of any radiation entering your body. There are reports of the takumar 50mm 1.4 lenses interfering with the mirror on the 6d so I would avoid it unless your willing to have a bit of the mirror shaved off the camera.

You can use Nikkor and Olympus lenses without an issue on that body but personally I'd opt for a mirrorless Sony system but that does restrict your AF lens choices.

$75 for a damaged 50mm F1.4 is a bit much tbh


I'd love to opt out for mirrorless but the finances are a little short right now to be honest. See, I first thought the 75€ was a good price since a good chunk of the Takumars you can get in my place of residence through spaces like eBay are often way over 150€ due to shipping and taxes. How much do you suggest it is worth? The ding is very small and I know for a fact that the lens is well centered. The seller sent me samples.


PostPosted: Thu May 12, 2022 4:39 am    Post subject: Reply with quote
I also think the price is a bit steep. 75€ is probably what I would pay for an example with no damage.


PostPosted: Thu May 12, 2022 7:45 am    Post subject: Reply with quote
caspert79 wrote:
I also think the price is a bit steep. 75€ is probably what I would pay for an example with no damage.


Well, again, any idea what an adequate price would be? As I said, here where I live they can usually be very expensive, over 150€ due to fees and shipping.


PostPosted: Thu May 12, 2022 7:46 am    Post subject: Reply with quote
visualopsins wrote:
Canon 5D mirror hits rear element of 7-element 1:1.4 / 50mm M42 TAKUMARs sometimes, but only when lens is focused to (or past) infinity. Turning focus ring slightly releases mirror without visible damage to mine over several years use with dozens of hits. Mine seemed to be temperature sensitive -- mirror did not hit in warm weather; hit more often when cold, sometimes only in portrait mode but not landscape, very intermittent.

The mirror hits 1:2 and 1:3.5 / 35mm TAKUMARS sometimes.

Forget the 1:3.5 / 24mm -- camera reports ERR99 and must be powered off and lens removed.

The mirror hits 1:4.5 / 20mm sometimes.

The FISHEYE, MACRO-TAKUMARs, and focal lengths greater than 50mm work fine -- no mirror hit.

Here's hoping that little front element "ding" is actually something that will easily clean off with a little solvent., such as water or lens cleaning fluid.


Thanks for the list, this will be helpful.


PostPosted: Thu May 12, 2022 9:18 am    Post subject: Reply with quote
Fandyus wrote:
caspert79 wrote:
I also think the price is a bit steep. 75€ is probably what I would pay for an example with no damage.


Well, again, any idea what an adequate price would be? As I said, here where I live they can usually be very expensive, over 150€ due to fees and shipping.


I think 100 € is reasonable for a very good example (the Super Multi Coated may fetch more), that's ex shipping. My estimation is that a little chip in the front element would probably halve that price. Not an issue probably when you use the lens, but maybe once you want to sell it again.


PostPosted: Thu May 12, 2022 10:11 am    Post subject: Reply with quote
This 7 element design was carried over into the k-mount. You can often find the SMC Pentax-m 50mm 1.4 for very reasonable prices and K-mount is also adaptable to Canon (same mirror issues of course). SMC coating makes the lens a bit less soft wide open. Other versions are SMC Pentax 50/1.4 (older) and SMC Pentax-A 50/1.4 (newer) the lens is still in production (in theory anyway) as the SMC Pentax FA 50mm 1.4 (AF version).


PostPosted: Thu May 12, 2022 7:16 pm    Post subject: Re: Some quick Super Takumar 50mm f/1.4 questions. Reply with quote
Fandyus wrote:
Hello.
I have recently found an offer to purchase a 7 element, 6 blade Super Takumar 50mm f/1.4 for around 75€. There's two things I need to know.
1. Is it usable on a Canon EOS 6D mk. I? It shouldn't protrude too far since it doesn't have 8 elements.
2. There is a tiny ding on the front element, the seller said he can physically feel it so it's not fungus like I worried. Is there any chance that this damage to the glass could end up leaking radioactive dust? Perhaps this is a paranoid question but I want to be sure.


2. No, the thorium element is at the back (5 and 6 out of 7) if it yellows its easy to clear with the sun or an ikea lamp.
Check Gerjan vanOosten radioactivity essay fir moire details


PostPosted: Thu May 12, 2022 7:58 pm    Post subject: Re: Some quick Super Takumar 50mm f/1.4 questions. Reply with quote
titrisol70 wrote:
Fandyus wrote:
Hello.
I have recently found an offer to purchase a 7 element, 6 blade Super Takumar 50mm f/1.4 for around 75€. There's two things I need to know.
1. Is it usable on a Canon EOS 6D mk. I? It shouldn't protrude too far since it doesn't have 8 elements.
2. There is a tiny ding on the front element, the seller said he can physically feel it so it's not fungus like I worried. Is there any chance that this damage to the glass could end up leaking radioactive dust? Perhaps this is a paranoid question but I want to be sure.


2. No, the thorium element is at the back (5 and 6 out of 7) if it yellows its easy to clear with the sun or an ikea lamp.
Check Gerjan vanOosten radioactivity essay fir moire details


As said already, no risk of radioactive dust with a ding on the front element of this lens.

Nevertheless, whilst thorium does not produce gamma radiation in the initial decay, its daughter elements further down the decay chain do produce some high energy gamma radiation. Whilst this isn't enough for concern when carrying the lens around on a day-trip, it is advisable not to store the lens within a two-meter radius or so of any place where a person can be spending extended cumulative periods of time (e.g. don't store it next to your bed or on your work-desk). Unlike alpha and beta radiation this high energy gamma radiation goes straight through even half a metre of lead, but intensity drops of very rapidly with distance (with a point source of radiation like a lens element), so keeping some distance when not in use is your only long-term option to keep radiation exposure to genuinely negligible limits.

Incidentally, they eventually stopped using thorium glass not no protect the consumer, but to protect the factory workers from the radioactive slurry produced during the grinding & polishing operations. This had become an issue e.g. when Swarovski was commissioned to make gun-sights with thorium glass for the Israeli army and some workers refused to work the glass (a gun sight is a dubious place to put a thorium element anyway, given its proximity to the eye!!). I learnt this from one of my colleagues whose father used to work for Swarovski.


PostPosted: Thu May 12, 2022 11:52 pm    Post subject: Re: Some quick Super Takumar 50mm f/1.4 questions. Reply with quote
RokkorDoctor wrote:
Unlike alpha and beta radiation this high energy gamma radiation goes straight through even half a metre of lead, ...


No.

Most gamma ray decays in the thorium series are in the range of 0.2 to 0.5 MeV. One centimeter of lead reduces 1 MeV gamma photons to 50%. Two centimeters of lead would reduce them to 25%, three cm to 12.5%, and so on. No way these gamma rays would go "straight through half a meter of lead" Wink!!

S


PostPosted: Fri May 13, 2022 9:02 am    Post subject: Re: Some quick Super Takumar 50mm f/1.4 questions. Reply with quote
stevemark wrote:
RokkorDoctor wrote:
Unlike alpha and beta radiation this high energy gamma radiation goes straight through even half a metre of lead, ...


No.

Most gamma ray decays in the thorium series are in the range of 0.2 to 0.5 MeV. One centimeter of lead reduces 1 MeV gamma photons to 50%. Two centimeters of lead would reduce them to 25%, three cm to 12.5%, and so on. No way these gamma rays would go "straight through half a meter of lead" Wink!!

S


My bad, I got my shielding materials confused. Concrete, not lead Wink. Faulty recollection from when I was looking at how much shielding was needed to survive the gamma radiation burst of an H-bomb... (don't ask).

Indeed, most of the gamma rays from the thorium decay chain are low enough energy to be stopped by a modest thickness of lead, but I do recall reading that it was the thallium-208 decay in the chain that is the problem with much higher energy gamma emissions at 2.6 MeV. I think it is much lower intensity in terms of %, but even in lead the mean free path of the Tl-208 gamma rays is still 20cm apparently, which is really rather long.

Carrying a lens for a couple of hours is rather different in terms of cumulative exposure compared to sleeping next to it 8 hours a day, 365 days a year, so I would still advise caution in terms of storing them long-term.

Incidentally (if memory doesn't fail me here Rolling Eyes ), I believe that storage of more than 5kg of Thorium becomes notifiable to the authorities (in the UK), but that would be a lot of lenses Wink
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